Publications

Here you will find an overview of my publications, sorted by year. For each publication I give the title, the citation and either the abstract or a short description of the content. A pdf of the paper can be downloaded by clicking on the PDF button. For papers for which I cannot provide a pdf on my website, you will find a link to the corresponding journal. Many of these papers are available on ResearchGate or can otherwise be requested by emailing me.

This page was last updated on: 22.02.2025

Accepted

2025

The osteology, taxonomy, and phylogenetic placement of Seeleyosaurus guilelmiimperatoris (Plesiosauroidea, Microcleididae) from the Lower Jurassic Posidonia Shale of Germany

Sachs, S., Madzia, D., Marx, M., Roberts, A., Hampe, O. & Kear, B.P. (2025) The osteology, taxonomy, and phylogenetic placement of Seeleyosaurus guilelmiimperatoris (Plesiosauroidea, Microcleididae) from the Lower Jurassic Posidonia Shale of Germany. The Anatomical Record: 1-62. 

---Seeleyosaurus guilelmiimperatoris is an early-diverging plesiosauroid from the lower Toarcian (Lower Jurassic) of the Posidonienschiefer Formation (Posidonia Shale) of Holzmaden, southwestern Germany. It is known from almost complete skeletons of two osteologically mature individuals, the holotype and a referred specimen that was largely destroyed during World War II. Although well-preserved and substantially complete, the anatomy of Seeleyosaurus and its taxonomic and phylogenetic significance remain insufficiently understood. Here, we provide a complete osteological description of the taxon. Seeleyosaurus guilelmiimperatoris can be diagnosed based on a unique combination of characters, including one autapomorphy: the tall and basally constricted neural spines of the posterior cervical, pectoral, and dorsal vertebrae which have a sinusoidal shape in lateral view. Our study supports the validity of the plesiosauroid taxon Plesiopterys wildi, which was considered a junior synonym of Seeleyosaurus in a previous joint assessment of the taxa. Our phylogenetic evaluation places S. guilelmiimperatoris among Microcleididae, in congruence with previous studies. However, in contrast to earlier phylogenetic reconstructions, our analyses, which take into account numerous changes to the character matrix, reconstruct S. guilelmiimperatoris as falling within the Microcleidus clade. While we admit that Seeleyosaurus might potentially be considered a species of Microcleidus, we refrain from promoting this nomenclatural change pending an osteological and taxonomic reassessment of Microcleidus spp. as well as other, potentially closely related forms, such as Lusonectes sauvagei.

Skin, scales, and cells in a Jurassic plesiosaur

Marx, M., Sjövall, P., Kear, B.P., Jarenmark, M., Eriksson, M.E., Sachs, S., Nilkens, K., Op De Beeck, M. & Lindgren, J. (2025) Skin, scales, and cells in a Jurassic plesiosaur. Current Biology 35: 1–8. 

---Plesiosaurs are an iconic group of Mesozoic marine reptiles with an evolutionary history spanning over 140 million years (Ma). Their skeletal remains have been discovered worldwide; however, accompanying fossilized soft tissues are exceptionally rare. Here, we report a virtually complete plesiosaur from the Lower Jurassic (∼183 Ma) Posidonia Shale of Germany that preserves skin traces from around the tail and front flipper. The tail integument was apparently scale-less and retains identifiable melanosomes, keratinocytes with cell nuclei, and the stratum corneum, stratum spinosum, and stratum basale of the epidermis. Molecular analysis reveals aromatic and aliphatic hydrocarbons that likely denote degraded original organics. The flipper integument otherwise integrates small, sub-triangular structures reminiscent of modern reptilian scales. These may have influenced flipper hydrodynamics and/or provided traction on the substrate during benthic feeding. Similar to other sea-going reptiles, scalation covering at least part of the body therefore probably augmented the paleoecology of plesiosaurs.

A re-description of the teleosauroid Macrospondylus bollensis (Jaeger, 1828) from the Posidonienschiefer Formation of Germany

Johnson, M.M., Sachs, S., Young, M.T. & Abel, P. (2025) A re-description of the teleosauroid Macrospondylus bollensis (Jaeger, 1828) from the Posidonienschiefer Formation of Germany. PalZ: 1-26. 

---Teleosauroid crocodylomorphs were a successful, diverse and abundant clade that expanded near-globally during the Jurassic Period. Teleosauroids are commonly found in Toarcian strata (Early Jurassic) within Europe, with multiple unique specimens pertaining to four taxa having been discovered in the Posidonienschiefer Formation (= Posidonia Shale) in southwestern Germany. The majority of these specimens have been referred to Macrospondylus bollensis (Jaeger, 1828), a basal machimosaurid species previously assigned to the genus Steneosaurus. Macrospondylus bollensis, as a species, is known to have a long and impressive history; unfortunately, the holotype of Ma. bollensis is poorly understood, rarely referenced in the current literature and is often incorrectly thought to be a teleosauroid specimen from Whitby. The actual holotype (housed at the Museum für Mineralogie und Geologie in Dresden), while badly burned, offers valuable information on basal teleosauroid postcranial material. We provide a detailed re-description of Macrospondylus bollensis, recognize it as a valid taxon and compare it with other Toarcian and machimosaurid teleosauroids. In addition, we evaluate the ecology and biogeographical distribution of Macrospondylus.

Paddelechsen aus Gronau

Schwermann, A.H. & Sachs, S. (2025) Paddelechsen aus Gronau. Jahrbuch des Kreises Borken 2025: 264-267.

---Die Plesiosaurier (Paddelechsen) sind eine faszinierende Tiergruppe des Mesozoikums (Erdmittelalter), also der Periode, die auch als Zeitalter der Dinosaurier bezeichnet wird. In der öffentlichen Wahrnehmung werden Plesiosaurier schnell in einem Atemzug mit Dinosauriern genannt. Tatsächlich handelt es sich um zwei voneinander getrennte Tiergruppen, die sich beide in der Trias (252-201 Millionen Jahre) entwickelt haben.  Während die sich Dinosaurier bekanntermaßen zu einer sehr diversen Gruppe landlebender Vierbeiner entwickelt haben, steht am Beginn der Plesiosaurier-Evolution eine, wenn man so möchte, Umkehr in der Lebensweise.

2024

Cricosaurinae Koken, 1888 (Archosauria, Crocodylomorpha, Metriorhynchidae): proposed emendation to Cricosaurusinae to remove homonymy with Cricosaurinae Cope, 1875 (Lepidosauria, Squamata, Xantusiidae)

Young, M.T, Herrera, Y., Wilberg, E., Sachs, S., Abel, P. & Andrade, M.B. (2024) Case 3871 – Case 3871 – Cricosaurinae Koken, 1888 (Archosauria, Crocodylomorpha, Metriorhynchidae): proposed emendation to Cricosaurusinae to remove homonymy with Cricosaurinae Cope, 1875 (Lepidosauria, Squamata, Xantusiidae). The Bulletin of Zoological Nomenclature 81(1): 53-61.

---The purpose of this application, under Article 55.3 of the ICZN Code, is to remove the homonymy between the unused Cricosaurinae Koken, 1888 (Archosauria, Crocodylomorpha, Metriorhynchidae) (type genus Cricosaurus Wagner, 1858) and the in-use senior homonym Cricosaurinae Cope, 1875 (Lepidosauria, Squamata, Xantusiidae) (type genus Cricosaura Gundlach & Peters in Peters, 1863). We propose to emend the stem of the name of the type genus of the unused Cricosaurinae Koken, 1888 from Cricosaur- to Cricosaurus-, which would result in Cricosaurusinae Koken, 1888. Reversal of precedence (Article 23.9 of the Code) is invoked for the subjective synonymy between Cricosaurini Koken, 1888, herewith treated as a nomen oblitum, and Rhacheosaurini Young, Bell & Brusatte, 2011, herewith treated as a nomen protectum.

Early-diverging plesiosaurs from the Pliensbachian (Lower Jurassic) of northwestern Germany

Sachs, S., Hornung, J.J. & Madzia, D. (2024) Early-diverging plesiosaurs from the Pliensbachian (Lower Jurassic) of northwestern Germany. PeerJ 12:e18408

---The knowledge of Pliensbachian (Early Jurassic, ∼192.9–184.2 Ma) plesiosaurs is notoriously insufficient. Although there have been specimens described from different parts of the world, only three of them have been established as diagnosable taxa. Here, we describe two previously unreported lower Pliensbachian plesiosaur occurrences that originate from two sites located in North Rhine-Westphalia, Germany. One of the new occurrences is represented by three cervical and three indeterminable vertebrae from Werther, the other includes two associated pectoral or anterior dorsal vertebrae from Bielefeld. Although highly incomplete, the Werther individual, which derived from the Uptonia jamesoni Zone, is found to represent the only reliably identified early Pliensbachian pliosaurid known to date. Its material is geographically and stratigraphically proximate to the late Pliensbachian pliosaurid Arminisaurus schuberti, found in a clay-pit located in the Bielefeld district of Jöllenbeck. However, even though the Werther plesiosaur and A. schuberti show a broadly similar morphology of the preserved cervical section, a precise identification of the Werther taxon is currently impossible.

Die Suche nach den verschollenen Knochen von Plesiosaurus kanzleri

Schwermann, A.H. & Sachs, S. (2024) Die Suche nach den verschollenen Knochen von Plesiosaurus kanzleri. Archäologie in Westfalen-Lippe 2023: 31-33.

---Plesiosaurier (Paddelechsen) sind eine Gruppe von Reptilien, die sich dadurch auszeichnet, dass sie vollständig an ein Leben im Meer angepasst war. Sie sind aus landlebenden Reptilien hervorgegangen und haben eine bemerkenswerte Umwandlung von Körperbau und Lebensweise durchlaufen. Aus den vier Extremitäten, die bei ihren Vorfahren noch für das Laufen auf festem Untergrund geeignet waren, haben sich bei den Plesiosauriern vier Paddel entwickelt. Der spindelförmige Körper ist eine Anpassung, wie man sie auch bei anderen, schnell schwimmenden Tieren bemerkt.

Assessing the hydro- and thermodynamic capabilities of long-necked plesiosaurs using computational fluid dynamics

Marx, M., Szász, R., Eriksson, M.E., Kear, B., Sachs, S. & Lindgren, J. (2024) Assessing the hydro- and thermodynamic capabilities of long-necked plesiosaurs using computational fluid dynamics. SVP 84th Annual Meeting Program Guide: 364.

---Reconstructing the appearance of ancient organisms is a major focal point of paleontological research. Typically, our ideas for life-like reconstructions derive from exquisitely preserved specimens with soft tissues. However, many animals are not commonly preserved with fossilized soft parts and among these are the plesiosaurs. These marine reptiles have a fossil record that extends over more than 130 million years during the Mesozoic Era, and their remains have been found in deposits representing both warm, equatorial waters and cold, highlatitude environments. Reconstructions of plesiosaurs are often characterized by a narrow, snake-like neck attached to sea turtle-like body. However, this design is at odds with the otherwise prevalent spindle- to torpedo-shaped bauplan of marine animals. Given the presence of plesiosaurs in coldwater environments, it is reasonable to assume that these secondarily aquatic reptiles utilized blubber for insulation, in similarity with modern-day whales and adult individuals of the leatherback turtle (Dermochelys coriacea). Blubber is also beneficial in enhancing streamlining, which reduces drag. To test this alternative scenario, a traditional long-necked form was 3D generated along with a blubber-lined geometry to assess their hydro- and thermodynamic capabilities using computational fluid dynamics. A model that is both hydrodynamic and thermodynamically efficient is here hypothesized as the most likely candidate for the actual appearance of a plesiosaur in life. Computational fluid dynamics is a burgeoning experimental approach in paleontology that holds great potential as an avenue to assess likelihood scenarios for reconstructions of the appearance and adaptations of extinct animals.

A new genus of metriorhynchid crocodylomorph from the Lower Cretaceous of Germany

Sachs, S., Young, M. T., Hornung, J. J., Cowgill, T., Schwab, J. A., & Brusatte, S. L. (2024) A new genus of metriorhynchid crocodylomorph from the Lower Cretaceous of Germany. Journal of Systematic Palaeontology 22(1): 2359946.

---Here we describe a new genus and species of metriorhynchid crocodylomorph, Enalioetes schroederi gen. et sp. nov., from the lower Valanginian Stadthagen Formation (Lower Cretaceous) of north-western Germany. Enalioetes schroederi is the most complete and well-preserved Cretaceous metriorhynchid skull known to date, preserving most of the cranium and mandible, the atlas-axis complex and the first postaxial cervical vertebra. The specimen was previously attributed to the coeval enigmatic metriorhynchid Enaliosuchus (a nomen dubium) and, more recently, to Cricosaurus. Although the specific epithet schroederi has been used frequently in the literature, it has never been formally established. Herein, we demonstrate that the new taxon is distinct from all known metriorhynchids by a unique combination of characters including several autapomorphies such as: the lack of bulbous dorsolateral expansion in the posterior nasal cavity; mediolateral distance between the orbital canals being approximately 1.5 times the diameter of the orbital canals; lacrimal with dorsoventrally deep anterior process ventral to the preorbital fossa being equal to or greater than the depth of the jugal anterior process and the anterodorsal process of the lacrimal; and ascending processes at atlas intercentrum extending far dorsally to level of neural canal. Enalioetes schroederi contributes to the sparse global record of Cretaceous metriorhynchids and represents one of the stratigraphically youngest occurrences of the group. It can thus help to enhance our understanding of the metriorhynchid diversity during the Cretaceous Period.

Recovering lost time in Syria: New Late Cretaceous (Coniacian-Santonian) elasmosaurid remains from the Palmyrides mountain chain

Alhalabi, W.A., Bardet, B., Sachs, S., Kear, B.P., Joude, I.B., Yazbek, M.K., Godoy, P.L. & Langer, M. C. (2024) Recovering lost time in Syria: New Late Cretaceous (Coniacian-Santonian) elasmosaurid remains from the Palmyrides mountain chain. Cretaceous Research 159: 105871.

---Despite its relatively limited vertebrate fossil record, Syria currently records the largest number of documented Mesozoic marine reptile occurrences among the Middle Eastern countries. In particular, the phosphatic deposits of the Palmyrides mountain chain have yielded fossils of aquatic squamates, bothremydid and chelonioid marine turtles, as well as elasmosaurid plesiosaurs. Nevertheless, new discoveries have not been reported for the last two decades. Here, we describe the partial skeleton of an elasmosaurid plesiosaur from Syria, which comprises the middle and posterior cervical series, together with articulated pectoral, dorsal and anterior caudal parts of the vertebral column, with associated rib fragments. The fossil was excavated from Coniacian-Santonian phosphatic deposits of the Al Sawaneh el Charquieh mines, in the central part of the southwestern Palmyrides, about 200 km northeast of Damascus. The specimen can be assigned to Elasmosauridae based on the cervical centra morphology and, although incomplete, is significant because it not only represents likely the oldest, but also the currently most complete plesiosaur skeleton recovered from the Middle East.

Exquisite skeletons of a new transitional plesiosaur fill gap in the evolutionary history of plesiosauroids

Sachs, S., Eggmaier, S. & Madzia, D. (2024) Exquisite skeletons of a new transitional plesiosaur fill gap in the evolutionary history of plesiosauroids. Frontiers Earth Sciences 12: 1-10.

---Plesiosaurs are Mesozoic reptiles fully adapted to an aquatic lifestyle. Throughout their evolutionary history exceeding 140 million years plesiosaurs dispersed globally, achieved substantial diversity, occupied a variety of ecological niches, and experienced multiple faunal turnovers. Of those, the Early/Middle Jurassic transition event (∼175–171 Mya) has recently became of increased interest because it apparently profoundly affected all three major lineages of plesiosaurs. Once dominant Rhomaleosauridae started to vanish, while Pliosauridae and Plesiosauroidea diversified and gave rise to several clades that flourished for tens of millions of years. Here, we report exquisite, three-dimensionally preserved skeletons of a new plesiosaur from the Lower Jurassic of Germany. Franconiasaurus brevispinus gen. et sp. nov. lived during the late Toarcian (∼175 Mya), near the onset of the Early–Middle Jurassic turnover. Franconiasaurus displays an intriguing mixture of features, combining characters almost uniformly distributed among early plesiosaurs with those typically observed in later-diverging members of the clade. Phylogenetic analyses firmly place Franconiasaurus as the sister taxon to Cryptoclidia, bridging an evolutionary gap between early plesiosauroids, such as Plesiosaurus-like forms and microcleidids, and later-diverging representatives of the clade, such as cryptoclidids, leptocleidians, and elasmosaurids.

The history, systematics, and nomenclature of Thalattosuchia (Archosauria: Crocodylomorpha)

Young, M.T., Wilberg, E.W., Johnson, M.M., Herrera, Y., Brandalise de Andrade, M., Brignon, A., Sachs, S., Abel, P., Foffa, D., Fernandez, M.S., Vignaud, P., Cowgill, T. & Brusatte, S.L. (2024) The history, systematics, and nomenclature of Thalattosuchia (Archosauria: Crocodylomorpha). Zoological Journal of the Linnean Society 200(2): 547–617.

---The use of more than one nomenclatural code is becoming increasingly common in some biological sub-disciplines. To minimize nomenclatural instability, we have decided to establish a higher level systematization for Thalattosuchia under both the International Code of Phylogenetic Nomenclature (‘PhyloCode’) and the International Code of Zoological Nomenclature (‘Zoological Code’). We undertook a series of phylogenetic analyses with an expanded dataset to examine the origins of Thalattosuchia within Crocodylomorpha, and determined the clade’s diagnostic characters. Based on these analyses, we provide updated diagnoses for Thalattosuchia and its subclades under both the PhyloCode and Zoological Code. We also introduce two new nomina that are regulated under the PhyloCode (Neothalattosuchia and Euthalattosuchia), and the nomen Dakosaurina, which is registered under both nomenclatural codes. Moreover, we introduce PhyloCode-compliant phylogenetic definitions for Thalattosuchia and its subclades. As we cannot reliably discriminate between the positional hypotheses for Thalattosuchia within Crocodylomorpha, the clades’ origins are as much of a mystery today as they were over a century ago. However, we hope that using the same diagnostic characters to define the same clades, with the same nomina, under both nomenclatural codes will be an example to others to follow.

2023

The rise of macropredatory pliosaurids near the Early-Middle Jurassic transition

Sachs, S., Madzia, D., Thuy, B. & Kear, B.P. (2023) The rise of macropredatory pliosaurids near the Early-Middle Jurassic transition. Scientific Reports 13: 17558

---The emergence of gigantic pliosaurid plesiosaurs reshaped the trophic structure of Mesozoic marine ecosystems, and established an  ~ 80 million-year (Ma) dynasty of macropredatory marine reptiles. However, the timescale of their ‘defining’ trait evolution is incompletely understood because the fossil record of gigantic pliosaurids is scarce prior to the late-Middle Jurassic (Callovian),  ~ 165.3 Ma. Here, we pinpoint the appearance of large body size and robust dentitions to early-Middle Jurassic (Bajocian) pliosaurids from northeastern France and Switzerland. These specimens include a new genus that sheds light on the nascent diversification of macropredatory pliosaurids occurring shortly after the Early-Middle Jurassic transition, around  ~ 171 Ma. Furthermore, our multivariate assessment of dental character states shows that the first gigantic pliosaurids occupied different morphospace from coeval large-bodied rhomaleosaurid plesiosaurs, which were dominant in the Early Jurassic but declined during the mid-Jurassic, possibly facilitating the radiation and subsequent ecomorph acme of pliosaurids. Finally, we posit that while the emergence of macropredatory pliosaurids was apparently coordinated with regional faunal turnover in the epeiric basins of Europe, it paralleled a globally protracted extinction of other higher trophic-level marine reptiles that was not completed until after the earliest-Late Jurassic,  ~ 161.5 Ma.

Unusual plesiosaur vertebrae from the Lower Jurassic Posidonia Shale of Germany

Sachs, S., Abel, P. & Madzia, D. (2023) Unusual plesiosaur vertebrae from the Lower Jurassic Posidonia Shale of Germany. Historical Biology 36(10):  2124-2132.

---The Toarcian (upper Lower Jurassic) strata of the world-renowned Posidonia Shale of Central Europe have yielded diverse assemblages of marine vertebrates. Some of them, such as those of the Holzmaden area in southwestern Germany, are among the best-preserved specimens of Lower Jurassic vertebrate taxa. Here, we provide a reassessment of ‘Plesiosaurus’ bavaricus, a long-overlooked plesiosaur taxon from the Posidonia Shale of northern Bavaria (southern Germany), established based upon two isolated cervical centra and a caudal vertebra. The cervical material exhibits an intriguing character combination, providing evidence for the presence of a distinct plesiosaur taxon in the upper Lower Jurassic of the Posidonia Shale of Germany. Additionally, we report another isolated cervical vertebra, likewise from the Posidonia Shale of Bavaria, that shows striking similarities to the type cervicals of ‘P’. bavaricus. Following our study of the Bavarian specimens, we hypothesise that, despite their substantial incompleteness, it seems likely that the material belonged to the same taxon, either species or a group of species, distinct from other plesiosaurs known from the Posidonia Shale.

Preserved skin with putative scales in a new plesiosaur from the Jurassic Posidonia Shale of Germany

Marx, M., Sjövall, P., Jarenmark, M., Eriksson, M.E., Kear, B., Sachs, S., Nilkens, K., Op De Beeck, M. & Lindgren, J. (2023) Preserved skin with putative scales in a new plesiosaur from the Jurassic Posidonia Shale of Germany. 8th International Meeting on Mesozoic fishes and aquatic tetrapods Abstract Volume: 39

---Little is known about the soft tissue anatomy of plesiosaurs, because documented specimens preserving non-skeletal body remains are extremely rare. However, a newly prepared plesiosauroid plesiosaur from the Lower Jurassic Posidonia Shale of Germany includes patches of soft tissues in the tail region and along the trailing edge of one forelimb. These were studied using an array of analytical techniques, including IR microspectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), electron microscopy, and thin sectioning. The results reveal the presence of residual epidermis (≤ 250 μm thick) with morphologically distinguishable stratum corneum and stratum spinosum. Both keratinocytes and the remains of melanophores are also visible. SEM and TEM imaging confirm the presence of remnant pigment cells with dense clusters of melanosome organelles. ToF-SIMS indicates the presence of aliphatics, aromatics, and possibly also degraded eumelanin. SEM imaging of demineralized tissue from the front flipper shows an absence of melanosomes, instead revealing what appears to be scale-like residues with layers visible in cross-section possibly corresponding to the Oberhaut, and β-keratin layers. In addition, a thin section of the forelimb tissue demonstrated a thin and dark exterior-most layer that might represent the scale surface stratum with underlying keratinocytes. Although removed during preparation, detailed pre-preparation photographs of the tail area served to indicate the presence of a fluke – only the second example ever recorded in a plesiosaur. In summary, our novel in-depth analysis of plesiosaur soft tissues demonstrates a relatively thick epidermis with putative scales covering at least the forelimbs. The occurrence of melanophores and melanosomes on the ventral side of the tail suggests a dark coloration in at least part of the animal.

A high-diversity assemblage of herbivorous dinosaurs from a Barremian-Aptian Paleoupland locality of Northwestern Germany

Hornung, J.J., Madzia, D., Sachs, S. & Schwermann, A.H. (2023) A high-diversity assemblage of herbivorous dinosaurs from a Barremian-Aptian Paleoupland locality of Northwestern Germany. – In: Alba, D.M., Marigó, J., Nacarino-Meneses, C., Villa, A. (Eds.), Book of Abstracts of the 20th Annual Conference of the European Association of Vertebrate Palaeontologists. Palaeovertebrata, Special Volume 1: 124. 

---Upland environments are severely underrepresented in the fossil record, which causes substantial gaps in our knowledge of their paleodiversity. Barremian–Aptian upland paleokarst fissure and cave deposits exposed at Balve-Beckum in northwestern Germany yield a large amount of vertebrate remains. Disarticulated and fragmentary bones and teeth represent a diverse vertebrate fauna that includes selachians, osteichthyans, lissamphibians, mammals, squamates, turtles, crocodyliforms, and pterosaurs, as well as ornithischian, theropod, and sauropodomorph dinosaurs. Sedimentological and taphonomical information indicate a complex, probably multiphasic history of enrichment, sorting, and deposition of the material within a cave system that was formed in Paleozoic carbonates. Abundant ornithopods and rare sauropods are represented by larger disarticulated bones and bone fragments, as well as by several isolated teeth. The current sample includes at least two morphotypes of iguanodontian teeth corresponding to different positions within the tooth row or, potentially, several taxa. Aside from rare fragments of larger individuals, sauropod remains include small tooth crowns, probably from hatchling-sized individuals, representing two morphotypes that indicate two different taxa. There are also small, isolated tooth crowns displaying ornithischian features. A minimum of five morphotypes are recognized, probably representing at least three different taxa. The morphotypes differ from other Early Cretaceous ornithischians known from wellsampled localities such as the Wessex and Weald basins. This indicates that a high diversity of herbivorous dinosaurs was present at Balve, which adds to the previously known faunal community at the site. Current research aims to elucidate the relationships, paleoecology, and taphonomy of this fauna.

A new ‘transitional’ plesiosaur from the uppermost Lower Jurassic of Germany

Sachs, S., Eggmaier, S. & Madzia, D. (2023) A new ‘transitional’ plesiosaur from the uppermost Lower Jurassic of Germany. – In: Alba, D.M., Marigó, J., Nacarino-Meneses, C., Villa, A. (Eds.), Book of Abstracts of the 20th Annual Conference of the European Association of Vertebrate Palaeontologists. Palaeovertebrata, Special Volume 1: 232. 

---Cryptoclidian plesiosaurs are a diverse and globally distributed clade of plesiosauroids that existed from the Middle Jurassic to the latest Cretaceous and comprised cryptoclidids, elasmosaurids, and leptocleidians. Their emergence is generally thought to be associated with the restructuring of the upper tier of marine ecosystems during the Early/Middle Jurassic transitional interval. However, no plesiosaur taxa have so far been discovered to bridge the gap between ‘typical’ plesiosauroid representatives of the Early Jurassic, such as microcleidids, and the ‘typical’ plesiosauroids of the Middle and Late Jurassic—the cryptoclidids. Here we report a new plesiosauroid taxon from the upper Toarcian (uppermost Lower Jurassic) of the Jurensismergel Formation of Mistelgau in Franconia, northern Bavaria, Germany. The new taxon is based upon two exquisite specimens, preserving most of the skeleton and including parts of the mandible, teeth, and a nearly complete postcranium. Phylogenetic analyses place the new plesiosauroid at a well-supported position as a sister taxon to Cryptoclidia, providing evidence for the presence of a ‘transitional’ plesiosaur that helps to fill the gap between the Early Jurassic and Middle to Late Jurassic plesiosaur faunas.

The first record of sauropod dinosaurs from a palaeotopographical upland environment and its implications for megaherbivorous dinosaur faunal turnover in the Early Cretaceous of northwestern Europe

Hornung, J.J., Sachs, S. & Schwermann, A.H. (2023) The first record of sauropod dinosaurs from a palaeotopographical upland environment and its implications for megaherbivorous dinosaur faunal turnover in the Early Cretaceous of northwestern Europe. Geologie und Paläontologie in Westfalen 97, 1-34.

---A fragmentary centrum of a dorsal vertebra and a manual ungual phalanx of eusauropod dinosaurs from the Upper Barremian – Lower Aptian of Balve in western Germany are described. The dorsal centrum shares potential synapomorphies with the enigmatic genus Ornithopsis and can probably be referred to a titanosauriform. The Balve record is of significance as it represents the only known direct evidence of this clade from an upland environment in Europe, which is assumed to have reached palaeoelevations of several hundred meters above sea level. Taphonomic signatures at some of the material from this site indicate prolonged surface exposure plus various stages of wear caused by water transport. The remains were finally deposited in sediment traps within a karst cave or fissure system. The fossil record suggests a retreat or shift of sauropod habitat range from coastal plains and lowlands to hinter- and uplands during the Early Cretaceous in northwest Europe. It is hypothesized that this was linked to the faunal replacement of low- and mid-level browsing sauropods (e.g. diplodocoideans) by iguanodontian ornithopods near the Jurassic-Cretaceous boundary in this region. High-browsing titanosauriform sauropods had small overlap in the trophic niche with the ornithopods, facilitating a sympatric coexistence of both groups. However, their range was dependent on highcanopy vegetation that was probably more abundant in uplands. The previously observed “mid-Cretaceous bottleneck” in sauropod diversity may therefore be a result of partial extinction and/or a sampling bias, as the preservation of upland faunas are very exceptional. However, it is be cautioned to interpolate these regional observations to global sauropod diversity patterns.

A 'long-forgotten' plesiosaur provides evidence of large-bodied rhomaleosaurids in the Middle Jurassic of Germany

Sachs, S., Abel, P. & Madzia, D. (2023). A 'long-forgotten' plesiosaur provides evidence of large-bodied rhomaleosaurids in the Middle Jurassic of Germany. Journal of Vertebrate Paleontology 42(5): e2205456

---Described in 1858, Trematospondylus macrocephalus is one of the earliest established plesiosaur taxa. However, despite being historically significant, the taxon disappeared from the literature shortly after its initial description and has not been mentioned for over a century. Thus, it has never been properly assessed. The holotype comprises seven vertebrae, including a supposed sacral vertebra and caudal vertebrae. The specimens were collected from the Lochen mountain massif near Balingen in southwestern Germany and derive from the Dentalienton Formation. As such, they are most likely early Bathonian (Middle Jurassic) in age. Here, we provide a thorough redescription of the material, illustrate it, and assess its phylogenetic affinities through a parsimony analysis. Our results show that T. macrocephalus shares characters with members of the Rhomaleosauridae, including, for example, the length-height ratio of the caudal centra as well as the placement of caudal ribs and hemapophyseal facets. Rhomaleosaurid affinities of the material are likewise supported by our phylogenetic analysis. Comparisons further indicate that the taxon belonged to large-bodied members of the clade, with a body length similar to that of Rhomaleosaurus. Even though the material does not enable Trematospondylus to be properly diagnosed, thus making it a nomen dubium, it still adds to the rare Middle Jurassic record of rhomaleosaurid plesiosaurs. At the same time, it enhances our knowledge of the plesiosaur taxic diversity during the pre-Callovian Middle Jurassic, which has been very limited.

2022

A new Early Cretaceous assemblage of iguanodontian dinosaurs from Western Germany

Sachs, S., Schwermann, A.H., Hornung, J.J. & Madzia, D. (2022) A new Early Cretaceous assemblage of iguanodontian dinosaurs from Western Germany. 82 Annual meeting of the Society of Vertebrate Paleontology, Abstracts: 291.

---The Lower Cretaceous (Barremian-Aptian) fissure filling at Balve in North Rhine-Westphalia (Western Germany) has yielded a diverse vertebrate fauna, comprising selachians, osteichthyes, amphibians, squamates, crocodiles, turtles, pterosaurs, theropod, sauropodomorph, and ornithischian dinosaurs, as well as mammals. The locality has been excavated since 2002 by the LWL Museum of Natural History in Münster and regular field seasons still provide new material every year. Within the past two decades a variety of ornithopod remains were uncovered at Balve. These comprise cranial remains (a partial dentary and isolated teeth) as well as postcranial material, including vertebrae, ribs, a sacrum, a scapula, pollex claws, and pelvic, and limb bone elements. The specimens can be largely assigned to Iguanodon-grade styracosternans. While most elements are isolated and show taphonomic wear, at least some equally sized vertebrae and the sacrum were found in close association and may belong to a single, immature individual. Larger elements (e.g., a vertebral centrum) match the size of adult Iguanodon bernissartensis specimens. Peripheral skeletal elements (pedal bones and caudal vertebrae) dominate quantitatively. Large bones are prone to be fragmented. The material potentially includes a robust and a gracile morphotype, but the disarticulated preservation and the presence of various ontogenetic stages require further investigation. The potential co-occurrence of a robust and gracile form would mirror coeval occurrences from England, Bernissart (Belgium), and the geographically close Nehden locality in Brilon (Germany).

The ultimate ‘Iffyosaur’ – an unusual ichthyosaur composite containing British and German material of different geological stages

Lomax, D.R., Sachs, S. & Hall, A. (2022) The ultimate ‘Iffyosaur’ – an unusual ichthyosaur composite containing British and German material of different geological stages. Paludicola 14(1): 32-42.

---Composite fossils can distort our evaluation of the morphology and variation of a species if unrecognised or misidentified. Many Early Jurassic ichthyosaurs collected during the 19th century have been identified as composites, but the problem is not restricted to historic specimens. More recently collected material, including some specimens for sale on the fossil market, are also composites or have been modified. One such specimen (RNHM F5672), said to be from the Lower Lias of Dorset, England, appears to be an almost complete skeleton, but comprises at least three individuals along with a carefully reconstructed and carved skull, and an apparent replica coracoid and forefin. The forefin, if a cast of a genuine specimen, shows a unique set of characters not previously observed in any ichthyosaur. Additionally, various caudal and dorsal vertebrae of indeterminate ichthyosaurs were pieced together to give the appearance of a complete, articulated vertebral column. One authentic block, containing the hindfins, the pelvic girdle and some ribs, can be assigned to Ichthyosaurus conybeari, based on characters of the hindfins. It comes from the Lower Jurassic (Sinemurian) of the Charmouth-Lyme Regis area, Dorset. The entire ‘skeleton’ is set into a large block of matrix which is from the Lower Jurassic (Toarcian) Posidonia Shale of Holzmaden, Germany. Therefore, this fossil represents a composite of material from multiple specimens belonging to perhaps two different genera, collected from two different countries and from two different geological stages.

Historical significance and taxonomic status of Ischyrodon meriani (Pliosauridae) from the Middle Jurassic of Switzerland

Madzia, D., Sachs, S. & Klug, C. (2022) Historical significance and taxonomic status of Ischyrodon meriani (Pliosauridae) from the Middle Jurassic of Switzerland. PeerJ 10: e13244

---Ischyrodon meriani is an obscure pliosaurid taxon established upon an exceptionally large tooth crown of a probable Callovian (Middle Jurassic) age that originates from Wölflinswil, Canton of Aargau, Switzerland. Despite being known for almost two centuries, the specimen remains poorly researched. Historically, I. meriani has been associated, or even considered conspecific, with Pliosaurus macromerus and Liopleurodon ferox. However, neither of the two hypotheses have been tested through detailed comparisons or using modern quantitative methods. Here, we redescribe the type of Ischyrodon meriani, illustrate it, and compare to teeth of thalassophonean pliosaurids, with special focus on Jurassic representatives of the clade. Multivariate analyses show close similarities to L. ferox but comparable structures to those of I. meriani, including a distinctive pattern of the apicobasal ridges, are also observable in some mid-Cretaceous brachauchenines from the ‘Polyptychodon’ assemblage of East and South East England. While it is likely that I. meriani represents a Liopleurodon-like taxon, or is indeed conspecific with L. ferox, which would make I. meriani the proper name for the species, any such taxonomic considerations are hindered by the fragmentary nature of the type specimens of both these taxa as well as limited knowledge of the dental variability within and between individual jaws of L. ferox. Currently, I. meriani is best treated as a nomen dubium. Finally, we discuss the potential implications of I. meriani being conspecific with L. ferox, and additionally provide a commentary on the taxonomic status of Liopleurodon.

Gyrosteus mirabilis – ein großer Störverwandter aus einem Ahrensburger Liasgeschiebe

Hornung, J.J. & Sachs, S. (2022) Gyrosteus mirabilis – ein großer Störverwandter aus einem Ahrensburger Liasgeschiebe. Fossilien 2022(4): 14-17.

---Die Chondrosteiden sind eine kleine Familie ursprünglicher, störartiger Fische im Unterjura Europas, von denen einige eine eindrucksvolle Größe erreichen konnten. Bislang sind aus marinen Ablagerungen Englands und Süddeutschlands drei Arten bekannt. Jetzt gelang zum ersten Mal der Nachweis des Chondrosteiden Gyrosteus mirabilis auch in einem liassischen Geschiebe von Ahrensburg bei Hamburg, dessen Ursprung im Baltischen Becken liegt.

2021

An anhanguerian pterodactyloid mandible from the lower Valanginian of Northern Germany, and the German record of Cretaceous pterosaurs

Abel, P., Hornung, J.J., Kear, B.P. & Sachs, S. (2021) An anhanguerian pterodactyloid mandible from the lower Valanginian of Northern Germany, and the German record of Cretaceous pterosaurs. Acta Palaeontologica Polonica 66(3): s005-s012

---The record of Cretaceous pterosaur remains from Germany is sparse. The material recovered to date includes the fragmentary holotypes of Targaryendraco wiedenrothi and Ctenochasma roemeri, as well as a few isolated pterodactyloid teeth and some indeterminate skeletal elements, together with a plaster cast of a large Purbeckopus manus imprint. Here, we report the discovery of a pterodactyloid pterosaur mandible from lower Valanginian strata of the Stadthagen Formation in the Lower Saxony Basin of Northern Germany. Based on the size and spacing of its alveoli, this fossil is attributable to the cosmopolitan Early Cretaceous pteranodontoid clade Anhangueria. Moreover, it represents the first and only known pterosaur from the Valanginian of Germany and is one of only a handful Valanganian pterosaur occurrences presently recognized worldwide. In addition to the approximately coeval Coloborhynchus clavirostris from the Hastings Bed Group of southern England, the Stadthagen Formation pterosaur mandible is among the stratigraphically oldest identifiable anhanguerians.

Das Drügendorfer Krokodil ein fränkischer Riese mit europaweiter Verwandtschaft

Abel, P., Sachs, S. & Young, M.T. (2021) Das Drügendorfer Krokodil ein fränkischer Riese mit europaweiter Verwandtschaft. Fossilien 2021(5): 24-31.

---Während des Mesozoikums haben sich mehrere Gruppen von Landreptilien unabhängig voneinander wieder an ein Leben im Meer angepasst. Neben den heute noch lebenden Meeresschildkröten waren es im Mesozoikum vor allem die Ichthyosaurier, Mosasaurier, sowie Plesiosaurier und andere Sauropterygier, die sich in den damaligen Meeren erfolgreich ausbreiten konnten. Eine weitere eher weniger bekannte, aber nicht minder erfolgreiche Gruppe waren die Thalattosuchier, ein Zweig von Meereskrokodilen, die vom Frühen Jura bis zum Ende der Frühen Kreide nahezu weltweit verbreitet waren. Während eine Gruppe der Thalattosuchier, die Teleosauroiden, oberflächlich heutigen Krokodilen wie den asiatischen Gavialen glichen, entstanden mit den Metriorhynchoiden auch Arten, die ähnlich zu den Ichthyosauriern und Mosasauriern verschiedene Anpassungen für ein dauerhaftes Leben im Meer entwickelten.

Equatorial pliosaurid from Venezuela marks the youngest South American occurrence of the clade

Bastiaans, D., Madzia, D., Carillo-Briceno, J.D. & Sachs, S. (2021) Equatorial pliosaurid from Venezuela marks the youngest South American occurrence of the clade. Scientific Reports 11, 15501.

---Pliosaurids were the dominant macropredators in aquatic environments at least since the Middle Jurassic until their extinction in the early Late Cretaceous. Until very recently, the Cretaceous record of Pliosauridae has been poor and difficult to interpret from the taxonomic and phylogenetic perspective. Despite that the knowledge of Cretaceous pliosaurids improved in recent years, numerous aspects of their evolutionary history still remain only poorly known. Here, we report the first pliosaurid material from Venezuela. The taxon is most likely earliest Cenomanian in age, thus representing the youngest occurrence of Pliosauridae from South America. The Venezuelan taxon is based on a well-preserved tooth crown whose morphology and outer enamel structural elements appear to resemble especially those observable in the giant pliosaurid Sachicasaurus vitae from the Lower Cretaceous of Colombia. The new discovery extends the pliosaurid record on the continent by more than 10 million years and likely marks the southernmost Upper Cretaceous occurrence of Pliosauridae, worldwide. We also briefly discuss the affinities of the enigmatic Venezuelan elasmosaurid Alzadasaurus tropicus and highlight similarities to elasmosaurids from the Western Interior Seaway.

A new species of Cricosaurus (Thalattosuchia, Metriorhynchidae) based upon a remarkably well-preserved skeleton from the Upper Jurassic of Germany

Sachs, S., Young, M.T., Abel, P. & Mallison, H. (2021) A new species of Cricosaurus (Thalattosuchia, Metriorhynchidae) based upon a remarkably well-preserved skeleton from the Upper Jurassic of Germany. Palaeontologia Electronica, 24(2): a24.

---Herein we describe a new and exceptionally well-preserved skeleton of the metriorhynchid thalattosuchian Cricosaurus from the upper Kimmeridgian Torleite Formation of Painten in Bavaria (Southern Germany). The specimen is articulated, shows soft-tissue preservation, and represents one of the most complete metriorhynchid skeletons known. The exceptional preservation allows us to explore the morphological variation of the tail region in the Metriorhynchidae, a part of the skeleton that has long been neglected. Based on our description and phylogenetic analyses, we name this specimen Cricosaurus albersdoerferi sp. nov. Our phylogenetic analyses recover a Cricosaurus subclade composed of four species from Southern Germany and one from Argentina. We provide revised diagnoses for the Southern German members of this subclade, revealing the presence of at least four closely-related Cricosaurus species in the late Kimmeridgian-early Tithonian of Southern Germany. Interestingly, within this subclade there is evidence of rapid change in tail construction and feeding ecology. However, there is no evidence of sympatry between these taxa, and the two species known from the same ammonite subzone are exclusively found in different northern-Tethys lagoons. Most interesting, however, is the variation in the skulls, dorsal neural spines, the tail displacement units, and flukes between these different species. This previously unexplored variation within Metriorhynchidae hints to differences in locomotory abilities between different species.

Evidence of two lineages of metriorhynchid crocodylomorphs in the Lower Cretaceous of the Czech Republic

Madzia, D., Sachs, S., Young, M.T., Lukeneder, A. & Skupien, P. (2021) Evidence of two lineages of metriorhynchid crocodylomorphs in the Lower Cretaceous of the Czech Republic. Acta Palaeontologica Polonica 66(2): 357-367.

---Metriorhynchid crocodylomorphs were an important component in shallow marine ecosystems during the Middle Jurassic to Early Cretaceous in the European archipelago. While metriorhynchids are well known from western European countries, their central and eastern European record is poor and usually limited to isolated or fragmentary specimens which often hinders a precise taxonomic assignment. However, isolated elements such as tooth crowns, have been found to provide informative taxonomic identifications. Here we describe two isolated metriorhynchid tooth crowns from the upper Valanginian (Lower Cretaceous) of the Štramberk area, Czech Republic. Our assessment of the specimens, including multivariate analysis of dental measurements and surface enamel structures, indicates that the crowns belong to two distinct geosaurin taxa (Plesiosuchina? indet. and Torvoneustes? sp.) with different feeding adaptations. The specimens represent the first evidence of Metriorhynchidae from the Czech Republic and some of the youngest metriorhynchid specimens worldwide.

Cranial osteology of the mid-Cretaceous elasmosaurid Thalassomedon haningtoni from the Western Interior Seaway of North America

Sachs, S., Lindgren, J., Madzia, D. & Kear, B.P. (2021) Cranial osteology of the mid-Cretaceous elasmosaurid Thalassomedon haningtoni from the Western Interior Seaway of North America. Cretaceous Research 123: 104769.

---Thalassomedon haningtoni is one of the most completely preserved elasmosaurid plesiosaurians described to date. Unlike most other elasmosaurid fossils, both the holotype and a second referred specimen — which were recovered from the middle Cenomanian Graneros Shale in the mid-western USA — are represented by intact skulls with articulated postcranial skeletons. Thalassomedon haningtoni thus constitutes an ideal ‘model elasmosaurid taxon’ that contributes significant character state data towards resolving contested relationships within the clade. Here, we present a detailed reassessment of the cranial osteology of T. haningtoni with the aim of evaluating its disputed species-level monophyly, together with its broader phylogenetic affinities. We identify several key diagnostic cranial traits including a sharply tapered premaxillary rostrum with a pronounced dorsomedian ridge that extends to the tip of the snout, a proportionately very small and rounded external bony nasal opening, and an anisodont functional dentition that incorporates a pair of enlarged ‘fangs’ in the second maxillary tooth position. Our phylogenetic analyses using first-hand scores unequivocally support classification of the Graneros Shale specimens as conspecific. Furthermore, consistent nesting with other North American elasmosaurid taxa suggests that T. haningtoni could evidence successive lineage divergences that took place within the Western Interior Seaway during the middle to latest Cretaceous.

Cutting the Gordian knot: a historical and taxonomic revision of the Jurassic crocodylomorph Metriorhynchus

Young, M.T., Brignon, A., Sachs, S., Hornung, J.J., Foffa, D., Kitson, J.J.N., Johnson, M.M. & Steel, L. (2021) Cutting the Gordian knot: a historical and taxonomic revision of the Jurassic crocodylomorph Metriorhynchus. Zoological Journal of the Linnean Society 192(2): 510–553.

---Metriorhynchidae was a clade of extinct crocodylomorphs that adapted to a pelagic lifestyle, becoming a key component of Mesozoic lagoonal and coastal marine ecosystems. The type genus Metriorhynchus is one of the best-known genera of Mesozoic crocodylomorphs, and since the mid-19th century, the ‘concept’ of Metriorhynchus has become associated with the referred species Me. superciliosus. Historically Metriorhynchus has been the most species-rich genus in Metriorhynchidae, with most Middle Jurassic species and many Late Jurassic species referred to the genus at some point in their history. However, the type species Me. geoffroyii has largely been omitted in the literature. Its type series is a chimera of multiple metriorhynchid species, and a type specimen has never been designated. Moreover, phylogenetic analyses have repeatedly shown that the 19th–20th century concept of Metriorhynchus is not monophyletic – to the point where only referring every metriorhynchid species, and some basal metriorhynchoids, to the genus would render it monophyletic. Herein we designate a lectotype for Me. geoffroyii, re-describe it and restrict the genus Metriorhynchus to the type species. We also establish the new genus Thalattosuchus for Me. superciliosus, thereby cutting the ‘Gordian knot’ of Metriorhynchus with Th. superciliosus.

Evidence of thalattosuchian crocodylomorphs in the Portland Stone Formation (Late Jurassic) of England, and a discussion on Cretaceous teleosauroids

Young, M.T. & Sachs, S. (2021) Evidence of thalattosuchian crocodylomorphs in the Portland Stone Formation (Late Jurassic) of England, and a discussion on Cretaceous teleosauroids. Historical Biology 33(9): 1473-1476.

---We report the first definite specimen of a thalattosuchian crocodylomorph from the Portland Stone Formation of England. This specimen (an isolated tooth crown) can be referred to the teleosauroid genus Machimosaurus based on its conical shape, distinctive enamel ornamentation and lack of carinae. Understanding the faunal composition of the Portland Stone Formation is key to elucidating the distinct shift in crocodylomorph taxa that occurred during the Tithonian-to-Berriasian in Europe. One of the most striking aspects of this faunal shift is the hypothesised extinction of Teleosauroidea in Europe. The presence of Machimosaurus in the Portland Stone Formation supports the hypothesis that the localised marine regression in Europe at the Jurassic–Cretaceous boundary, and the resultant habitat loss, contributed to the absence of teleosauroids in Europe during the Berriasian. However, the fossil record of thalattosuchians during the Cretaceous is notorious scarce. We review the purported Cretaceous record of teleosauroids, and agree that closer to the equator this clade survived for at least 20 million years after the Jurassic–Cretaceous boundary.

2020

The enigma of Enaliosuchus, and a reassessment of the Lower Cretaceous fossil record of Metriorhynchidae

Sachs, S., Young, M. T. & Hornung, J.J. (2020) The enigma of Enaliosuchus, and a reassessment of the Lower Cretaceous fossil record of Metriorhynchidae. Cretaceous Research 114: 104479. 

---Enaliosuchus macrospondylus Koken, 1883 was one of the first thalattosuchian taxa from the Cretaceous to be described. The type series includes an atlas-axis complex, remnants of three post-axial cervical vertebrae, several dorsal vertebrae, a caudal vertebra, an incomplete femur and a fragmentary sacral rib from the upper Valanginian of northern Germany. Additionally, two isolated, non-thalattosuchian, tooth crowns from the uppermost Valanginian to lowermost Hauterivian of different localities in northern Germany were tentatively assigned to E. macrospondylus by Koken. The taxon was established for the distinctive the atlas-axis morphology, in particular the apparent lack of an axis parapophysis. Enaliosuchus macrospondylus has been considered a valid taxon in recent studies, based upon a largely complete metriorhynchid specimen from the Valanginian of France that had been referred to this taxon, an assignment that has never been questioned. Here we provide a detailed re-description of the E. macrospondylus holotype specimen and determine whether it is diagnostic, and if a referral of the French specimen to E. macrospondylus is justified. We also discuss whether E. macrospondylus and another metriorhynchid specimen from the Valanginian of northern Germany, described as Enaliosuchus schroederi, are conspecific. Finally, we provide an overview of the current knowledge of metriorhynchid diversity during the Cretaceous.

Reassessment of Enaliosuchus schroederi, a metriorhynchid crocodylomorph from the Lower Cretaceous of northern Germany

Sachs, S., Young, M. T. & Hornung, J.J. (2020) Reassessment of Enaliosuchus schroederi, a metriorhynchid crocodylomorph from the Lower Cretaceous of northern Germany. 2nd Palaeontological Virtual Congress. Book of abstracts: 141.

---During the Jurassic, metriorhynchid crocodylomorphs radiated in marine ecosystems. However, their Cretaceous fossil record is sparse. This hampers our understanding of their marine specialisations, particularly as the first evidence mesopelagic adaptations are seen in Valanginian specimens. One of the best preserved Cretaceous metriorhynchids is the holotype of Enaliosuchus schroederi, comprising a three-dimensionally preserved skull (lacking the anterior rostrum), atlas-axis, first postaxial cervical vertebra, and associated ribs. The specimen derives from the lower Valanginian Stadthagen Formation and was found in a now abandoned clay pit in Sachsenhagen, northern Germany. Initially referred to the genus Enaliosuchus in 1921 by Schroeder, Kuhn (1936) later named the specimen Enaliosuchus schroederi. Later studies disagreed on the taxonomic status of Enaliosuchus, its type species E. macrospondylus and whether E. schroederi is a valid species. Most recently both species have been referred to the Late Jurassic genus Cricosaurus. Our reassessment of the type material of E. macrospondylus and E. schroederi found clear differences in their atlas-axis morphologies, validating E. schroederi as a distinct taxon. These differences include: the atlas intercentrum extending to the dorsal part of the atlas centrum in E. schroederi whereas it only extends to the midsection of the atlas centrum in E. macrospondylus. The E. schroederi skull is also diagnostic, in lacrimal and sclerotic ring morphology, and orbit size. These craniofacial differences are significant when compared to the Late Jurassic Cricosaurus species. Our reassessment of the Enaliosuchus schroederi holotype begins to elucidate metriorhynchid morphological diversity at the zenith of their marine adaptations.

Convergent evolution and possible constraint in the posterodorsal retraction of the external nares in pelagic crocodylomorphs

Young, M.T., Sachs, S., Abel, P., Foffa, D., Herrera, Y. & Kitson, J.J.N. (2020) Convergent evolution and possible constraint in the posterodorsal retraction of the external nares in pelagic crocodylomorphs. Zoological Journal of the Linnean Society 189: 494-520.

---Amongst Mesozoic marine reptiles, metriorhynchid crocodylomorphs were unique in evolving into pelagically adapted forms with little-to-no posterodorsal retraction of the external nares. Narial retraction is a common adaptation seen in sustained swimmers, notably occurring during cetacean evolution. Mesosaurids and the basalmost known members of ichthyosauriforms, thalattosaurians, saurosphargids, sauropterygians, pleurosaurids and mosasauroids had the external nares divided by an ossified bar, bound by multiple cranial bones and were positioned back from the tip of the rostrum. However, metriorhynchids evolved from taxa with a single external naris bound solely by the premaxilla, and positioned near the tip of an elongate rostrum. We posit that metriorhynchids were uniquely disadvantaged in evolving into sustained swimmers. Herein we describe three Late Jurassic metriorhynchid cranial rostra that display differing degrees of narial retraction. In our new phylogenetic analyses, the backwards migration of the narial fossa posterior margin occurred independently at least four times in Metriorhynchidae, whereas the backwards migration of the anterior margin only occurred twice. Although Rhacheosaurini share the backwards migration of the anterior and posterior narial margins, posterodorsal retraction occurred differently along three lineages. This culminated in the Early Cretaceous, where a rhacheosaurin evolved nares bound by the premaxilla and maxilla, and significantly posterodorsally retracted.

Inner ear sensory system changes as extinct crocodylomorphs transitioned from land to water

Schwab, J.A., Young, M.T.,  Neenan, J.M.,  Walsh, S.A., Witmer, L.M., Herrera, Y., Allain, R., Brochu, C.A., Choiniere, J.N., Clark, J.M., Dollman, K.N., Etches, S., Fritsch, G., Gignac, P.M., Ruebenstahl, A., Sachs, S., Turner, A.H., Vignaud, P., Wilberg, E.W., Xu, X., Zanno, L.E. & Brusatte, S.L. (2020) Inner ear sensory system changes as extinct crocodylomorphs transitioned from land to water. PNAS 117(19): 10422-10428.

---Major evolutionary transitions, in which animals develop new body plans and adapt to dramatically new habitats and lifestyles, have punctuated the history of life. The origin of cetaceans from land-living mammals is among the most famous of these events. Much earlier, during the Mesozoic Era, many reptile groups also moved from land to water, but these transitions are more poorly understood. We use computed tomography to study changes in the inner ear vestibular system, involved in sensing balance and equilibrium, as one of these groups, extinct crocodile relatives called thalattosuchians, transitioned from terrestrial ancestors into pelagic (open ocean) swimmers. We find that the morphology of the vestibular system corresponds to habitat, with pelagic thalattosuchians exhibiting a more compact labyrinth with wider semicircular canal diameters and an enlarged vestibule, reminiscent of modified and miniaturized labyrinths of other marine reptiles and cetaceans. Pelagic thalattosuchians with modified inner ears were the culmination of an evolutionary trend with a long semiaquatic phase, and their pelagic vestibular systems appeared after the first changes to the postcranial skeleton that enhanced their ability to swim. This is strikingly different from cetaceans, which miniaturized their labyrinths soon after entering the water, without a prolonged semiaquatic stage. Thus, thalattosuchians and cetaceans became secondarily aquatic in different ways and at different paces, showing that there are different routes for the same type of transition.

Metriorhynchid crocodylomorphs from the lower Kimmeridgian of Southern Germany: evidence for a new large-bodied geosaurin lineage in Europe

Abel, P., Sachs, S. & Young, M. T. (2020) Metriorhynchid crocodylomorphs from the lower Kimmeridgian of Southern Germany: evidence for a new large-bodied geosaurin lineage in Europe. Alcheringa 44(2): 312-326.

---Over the last two centuries, numerous exquisitely preserved thalattosuchian crocodylomorph skeletons have been found in the Jurassic strata of Southern Germany. While the majority of these specimens occur in Toarcian and upper Kimmeridgian–lower Tithonian deposits, thalattosuchian remains are otherwise rare in strata representing different stages of the Jurassic. Here, we describe skeletal elements from two large-bodied thalattosuchians attributable to the family Metriorhynchidae – these were recovered from lower Kimmeridgian sediments in Bavaria and Baden-Württemberg, respectively. These new metriorhynchid fossils are closely comparable in both stratigraphic age and dental morphology, and thus may be congeneric. Furthermore, our phylogenetic analysis suggests affinity with metriorhynchid remains from France, Switzerland, and the UK. We interpret these taxa as members of an as-yet unnamed geosaurine metriorhynchid lineage (herein termed the ‘E-clade’) from the Kimmeridgian and Tithonian of Europe, which appears to be related to species of Torvoneustes from England and Mexico, and Purranisaurus potens from Argentina, collectively contributing to ‘Subclade T’ of the tribe Geosaurini. Finally, the metriorhynchid material described herein suggests preservation as a ‘bloat and float’ carcass that underwent diagenetic dispersal within a limestone-marl-alternation deposited in an off-shore epicontinental marine environment.

Enigmatic plesiosaur vertebral remains from the middle Turonian of Germany

Sachs, S., Madzia, D., Püttmann, T. & Kear, B.P. (2020) Enigmatic plesiosaur vertebral remains from the middle Turonian of Germany. Cretaceous Research 110: 104406. 

---The Turonian (93.9-89.8 Ma) was a key transitional interval of plesiosaur evolution, during which pliosaurid apex predators (dominant since the Middle Jurassic) rapidly declined, and polycotylids correspondingly radiated as middle trophic-level pursuit hunters. Paradoxically, however, the fossil record of Turonian plesiosaurs is globally sparse, especially in continental Europe where only a handful of fragmentary specimens have been recovered from localities in the Czech Republic, Germany and Poland. Here, we report on a new European Turonian plesiosaur occurrence from the Bochum Grünsand Member of the Duisburg Formation in the city of Unna, western Germany. These remains comprise a series of eight mid-series cervical vertebrae with articulated ribs that can be precisely correlated to the lower middle Turonian UC8aeUC8b calcareous nannofossil biozones. The vertebrae display a distinctive character state combination, including transversely broad lozenge-shaped centra that are anteroposteriorly compact, bear amphicoelous articular surfaces, inset lateral sides, and large zygapophyses that are broader than the corresponding centra. Although phylogenetically inconclusive, these features are compatible with coeval polycotylids. The Bochum Grünsand Member vertebrae thus augment the currently scant knowledge of Turonian plesiosaurs from Europe, and support assertions that the regional assemblage was taxonomically diverse at that time. 

First record of Gyrosteus mirabilis (Actinopterygii, Chondrosteidae) from the Toarcian (Lower Jurassic) of the Baltic region

Hornung, J. & Sachs, S. (2020) First record of Gyrosteus mirabilis (Actinopterygii, Chondrosteidae) from the Toarcian (Lower Jurassic) of the Baltic region. PeerJ 8:e8400.

---An isolated hyomandibula from a lower Toarcian carbonate concretion of the Ahrensburg erratics assemblage (Schleswig-Holstein, northern Germany) represents the first record of a chondrosteid fish from the Lower Jurassic of the southwestern Baltic realm. Except for its smaller size, the specimen is morphologically indistinguishable from corresponding elements of Gyrosteus mirabilis from the Toarcian of Yorkshire, England. This find, which probably originates from the western Baltic basin between Bornholm Island (Denmark) and northeastern Germany, markedly expands the known range of this chondrosteid taxon across the northern part of the strait connecting the Boreal Sea with the Tethys Ocean during the Early Jurassic. For the first time the extension of the paleogeographic range of a chondrosteid species beyond its type area is documented, which can contribute to future studies of vertebrate faunal provincialism during the Lower Jurassic in Europe.

2019

Rare evidence of a giant pliosaurid-like plesiosaur from the Middle Jurassic (lower Bajocian) of Switzerland

Sachs, S., Klug, C & Kear, B.P. (2019) Rare evidence of a giant pliosaurid-like plesiosaur from the Middle Jurassic (lower Bajocian) of Switzerland. Swiss Journal of Palaeontology 138: 337–342. 

---Here, we describe part of a large-bodied macrophagous plesiosaur jaw from the lower Bajocian (Middle Jurassic) Passwang Formation near Arisdorf in the Basel-Land canton of Switzerland. The specimen preserves the posterior glenoid extremity of the right mandibular ramus comprising the surangular, angular, articular, and probably the prearticular. Notable character states include a transversely expanded surangular that incorporates a prominent medial ridge adjacent to the glenoid and a shallow dorsal fossa, together with a conspicuous trough extending across the lateral surfaces of both the surangular and angular; there is also a basally broad and medially deflected retroarticular process. Collectively, these features suggest affinities with Middle–Late Jurassic pliosaurids, as well as some coeval rhomaleosaurids. Based on such comparisons, we estimate that the Passwang Formation mandible was approximately 1.5 m long when complete, and thus approaches the size range of the largest-known pliosaurids. This discovery supplements the sparse record of diagnostic pliosaurid-like remains from Switzerland and contributes to the currently incomplete knowledge of pre-Callovian Middle Jurassic plesiosaurs globally.

Behind the Scenes at the Museum - Naturkunde-Museum Bielefeld, Germany

Sachs, S. & Keiter, M. (2019) Behind the Scenes at the Museum - Naturkunde-Museum Bielefeld, Germany. The Palaeontology Newsletter 102: 27-31.

---The Naturkunde-Museum Bielefeld is a municipal natural history museum with a long history. Initially the natural history collections were part of the Museum der Stadt Bielefeld (Museum of the city of Bielefeld), established on 3rd October 1906, that encompassed a history and a nature department. These departments were separated and formed independent museums in 1930 (Keiter and Sachs 2018). The Natural History Museum moved into the Kaselowsky villa where it remained until World War II when the collections were moved to rural locations in order to protect them from Allied bombings. After the war, no permanent home could be found for almost 20 years (from 1946 to 1964). During this time, the collection, neglected and distributed among several attics, suffered heavily. A large number of specimens was lost.

The mystery of Mystriosaurus: Redescribing the poorly known Early Jurassic teleosauroid thalattosuchians Mystriosaurus laurillardi and Steneosaurus brevior

Sachs, S., Johnson, M.M., Young, M.T. & Abel, P. (2019) The mystery of Mystriosaurus: redescribing the poorly known Early Jurassic teleosauroid thalattosuchians Mystriosaurus laurillardi and Steneosaurus brevior. Acta Palaeontologica Polonica 64(3): 565-579.

---The genus Mystriosaurus, established by Kaup in 1834, was one of the first thalattosuchian genera to be named. The holotype, an incomplete skull from the lower Toarcian Posidonienschiefer Formation of Altdorf (Bavaria, southern Germany), is poorly known with a convoluted taxonomic history. For the past 60 years, Mystriosaurus has been considered a subjective junior synonym of Steneosaurus. However, our reassessment of the Mystriosaurus laurillardi holotype demonstrates that it is a distinct and valid taxon. Moreover, we find the holotype of "Steneosaurus" brevior, an almost complete skull from the lower Toarcian Whitby Mudstone Formation of Whitby (Yorkshire, UK), to be a subjective junior synonym of M. laurillardi. 

A possible anhangueran pterosaur mandible from the Lower Cretaceous of Germany

Abel, P., Hornung, J.J., Kear, B.P. & Sachs, S. (2019) A possible anhangueran pterosaur mandible from the Lower Cretaceous of Germany. Program and abstracts. XVII Conference of the EAVP – Brussels, Belgium 2 – 6 July 2019: 7.

---Cretaceous pterosaur fossils are rare in Germany. The specimens documented to date are limited to only a few fragmentary body fossils and footprint traces from different Lower Cretaceous strata. Here we add to this sparse, but palaeobiogeographically significant record with the description of an incomplete mandible from marine sediments of the lower Valanginian Stadthagen Formation of Sachsenhagen in northern Germany. The remains are represented by the posterior section of a gracile symphyseal rostrum with a delicate midline ridge along its ventral edge. A pronounced lateral longitudinal groove also extends below the alveolar rim. Broken tooth crowns are preserved in the mesiodistally elongate alveoli, which are widely spaced (increasingly so posteriorly) and labially inclined without raised rims. Although precise generic affinities are uncertain, the shape and arrangement of the alveoli are reminiscent of Camposipterus nasutus Seeley 1869, from the Albian of England (which was defined on the basis of an incomplete cranial rostrum), as well as mandibles of the putative anhangueran taxon Cearadactylus atrox Leonardi & Borgomanero 1985, together with the unequivocal anhanguerids Anhanguera piscator Kellner & Tomida 2000, Tropeognathus mesembrinus Wellnhofer 1987, and Ludodactylus sibbicki Frey et al. 2003, (all of which additionally share the presence of a symphyseal ridge). We therefore conclude that the Stadthagen Formation pterosaur potentially constitutes one of the stratigraphically earliest occurrences of Anhangueria, and is at present the only known exemplar of this recovered from Germany.

Reassessment of the enigmatic pterosaur ‘Ornithocheirus’ wiedenrothi from the Lower Cretaceous of northern Germany

Abel, P., Hornung, J.J., Kear, B.P. & Sachs, S. (2019) Reassessment of the enigmatic pterosaur ‘Ornithocheirus’ wiedenrothi from the Lower Cretaceous of northern Germany. Starck, M. & Huysseune, A. (eds) International Congress of Vertebrate Morphology (ICVM) Abstract Issue 2019. Journal of Morphology, Supplement 280: S73-S74.

---In stark contrast to the famously rich Jurassic fossil record, the documented occurrences of Cretaceous pterosaur remains from Germany are extremeley sparse. To date, only a few bones and footprint traces have been found in strata of Berriaisian–Hauterivian age. The most complete and best-preserved of these specimens is the holotype of ‘Ornithocheirus’ wiedenrothi from the lowermost Hauterivian (Endemoceras amblygonium Zone) Stadthagen Formation of Engelbostel, near Hanover in Lower Saxony, northern Germany. This fragmentary skeleton comprises parts of the mandible, including a long symphyseal rostrum, some forelimb elements, and a section of a dorsal rib. The mandible displays several distinctive features, most notably, an anteriorly directed spur-like process at the tip of the mandibular symphysis, and an enlarged and anterodorsally inclined pair of teeth at the first tooth position in the jaw (these are also bordered by a prominent sulcus). When first described in 1990, ‘O.’ wiedenrothi was assigned to Ornithocheirus based on similarities with ‘Ornithocheirus’ compressirostris, which was then classified as the type species of the genus. However, ‘O.’ compressirostris has since been referred to Lonchodectes, which resembles ‘O.’ wiedenrothi in its lanceolate mandibular rostrum, and oval alveolar profile with raised alveolar ridges. ‘Ornithocheirus’ wiedenrothi is not directly comparable with the likely monotypic Ornithocheirus sensu stricto as no equivalent mandibular elements have been recovered for the type species O. simus. Consequently, while we concur with lonchodectid affinity, we consider ‘O.’ wiedenrothi to possibly represent a separate genus, and thus a novel addition to the Early Cretaceous pterosaur diversity of Europe.

A new species of the metriorhynchid crocodylomorph Cricosaurus from the Upper Jurassic of southern Germany

Sachs, S., Young, M., Abel, P. & Mallison, H. (2019) A new species of the metriorhynchid crocodylomorph Cricosaurus from the Upper Jurassic of southern Germany. Acta Palaeontologica Polonica 64(2): 343-356.

---Here we describe a new species of the metriorhynchid thalattosuchian Cricosaurus, C. bambergensis sp. nov., from the Upper Jurassic Torleite Formation of Wattendorf near Bamberg, Bavaria (southern Germany). The holotype and only known specimen is a nearly complete skeleton that shows a number of diagnostic traits including a bicarinate dentition formed by labiolingually compressed tooth crowns that lack a conspicuous enamel ornamentation and the presence of a distinct midline ridge with paired depressions on the palatines. Our phylogenetic analysis recovers a grouping of Cricosaurus bambergensis sp. nov. with C. elegans and C. suevicus. The implications of the new Cricosaurus species to the species complex from the late Kimmeridgian–early Tithonian of southern Germany is discussed. Our description of C. bambergensis demonstrates that the specific, and morphological, diversity of Cricosaurus in southern Germany was higher than previously thought. This coincides with the recent trend of re-evaluating the species-complexes of extant taxa, and the identification of new “cryptic species”. As such, the crocodylomorph fossil record will need to be re- examined to ensure there is not an underestimation of their biodiversity.

Morphological and phylogenetic aspects of the dentition of Megacephalosaurus eulerti, a pliosaurid from the Turonian of Kansas, USA, with remarks on the cranial anatomy of the taxon

Madzia, D., Sachs, S. & Lindgren, J. (2019) Morphological and phylogenetic aspects of the dentition of Megacephalosaurus eulerti, a pliosaurid from the Turonian of Kansas, USA, with remarks on the cranial anatomy of the taxon. Geological Magazine 156(7): 1201-1216.

---Megacephalosaurus eulerti is a large macropredatory plesiosaur representing one of the last members of the diverse pliosaurid clade Brachaucheninae. The taxon was established upon a nearly complete skull including the mandible and fragments of the postcranial skeleton originating from the lower middle Turonian (Upper Cretaceous) of Kansas, USA. Owing to its age, reasonable completeness and its state of preservation, M. eulerti bears important anatomical details regarding the last brachauchenines. Here we assess the dentition of the taxon, compare the teeth to those of other thalassophonean pliosaurids and comment on the utility of these results for inferences of the phylogenetic relationships of the last brachauchenines. Additionally, we provide remarks on the cranial anatomy of M. eulerti, revise character scores of this taxon used in current phylogenetic studies and address the phylogenetic relationships within Brachaucheninae. Parsimony analyses, aimed to test different character sampling and tree-search strategy, inferred only a single unambiguous synapomorphy uniting a clade formed by mid- to Late Cretaceous brachauchenines: presence of subcircular rather than subtrihedral/trihedral cross-sectional shape of the teeth. Still, the last brachauchenines (Brachauchenius and Megacephalosaurus) can be roughly characterized by a switch from anisodont to subisodont dentition and reduction of their tooth count. Nevertheless, the overall knowledge of the origin, phylogenetic relationships and distinguishability of brachauchenine pliosaurids remains poor and represents a subject for further extensive studies and modifications in taxon and character sampling. 

Filling the biostratigraphical gap: first choristoderan from the Lower–mid-Cretaceous interval of Europe

Reiss, S., Scheer, U., Sachs, S. & Kear, B.P. (2019) Filling the biostratigraphical gap: first choristoderan from the Lower–mid-Cretaceous interval of Europe. Cretaceous Research 96: 135-141. 

---Choristodera is a clade of extinct aquatic reptiles whose fossils have been found in freshwater and marginal marine deposits from Europe, Asia and North America. The European record is the most extensive, spanning at least the Middle Jurassic to early Miocene, and incorporates the stratigraphically oldest and youngest members of the group. Despite this, there is an unexplained ∼70 myr gap in European choristoderan fossil occurrences. Here we fill this hiatus with the discovery of an isolated choristoderan dorsal vertebra from the lower Cenomanian ‘Rotkalk’ red limestone facies of the Essen Greensand Formation in Mülheim/Ruhr, North Rhine-Westphalia, western Germany. This specimen represents the first identifiable European choristoderan from the Kimmeridgian–Campanian interval, and displays a diagnostic state combination including an amphiplatyan centrum with synapophyses on the transverse processes that are level with the neurocentral suture. The palaeobiogeographical distribution of choristoderans thus likely transected the entire Laurasian landmass throughout the Cretaceous, with perceived stratigraphical interstices being a result of incomplete sampling. 

2018

Plesiosaurier-Funde aus dem Mittleren Jura von Hildesheim

Sachs, S. & Nyhuis, C. (2018) Plesiosaurier-Funde aus dem Mittleren Jura von Hildesheim. Naturhistorica 160: 115-128.

---Plesiosaurier-Reste aus dem Mittleren Jura der Tongrube Temme in Hildesheim werden beschrieben. Das Material umfasst einen großen unvollständigen Zahn sowie diverse postcraniale Reste. Eine sichere Zuordnung zur Gattung Liopleurodon ist für den Zahn möglich. Isolierte Cervicalwirbel zeigen typische Merkmale der Familie Pliosauridae, und ein unvollständiges distales Ende eines Propodiums stammt vermutlich ebenfalls von einem Vertreter diese Gruppe. Weitere isolierte Cervicalwirbel können cryptoclididen Plesiosauriern zugeordnet werden. Die Hildesheimer Reste ergänzen die spärlichen Plesiosaurier-Funde aus dem Mittleren Jura Deutschlands. Nach Kenntnis der Autoren sind das die ersten Belege dieser Gruppe aus dem Mittleren Jura von Niedersachsen.

A global perspective on Mesozoic marine amniotes

Sachs, S., Lindgren J. & Kear, B.P. (2018) A global perspective on Mesozoic marine amniotes. Alcheringa 42(4): 457-460

---Mosasaurs are squamates that became the dominant predatory marine reptiles in the Late Cretaceous about 98–66 million years ago. Although early members of this group possessed body profiles similar to living terrestrial lizards, many of the later, more derived forms were streamlined and equipped with finlike limbs and a bilobed (hypocercal) tail fluke that would have enabled powerful swimming (Lindgren et al. 2010). Ecomorphological comparisons indicate that mosasaurs were probably very similar to modern pelagic sharks in terms of their hydrodynamic performance, and thus are convergent in both body form and locomotory style with other highly modified secondarily aquatic amniotes, including advanced ichthyosaurians (which were extremely specialised basallybranching non-saurian diapsids) and whales (Lindgren et al. 2011).

Ein Plesiosaurier aus dem Amaltheenton (Pliensbachium, Jura) von Bielefeld

Sachs, S. (2018) Ein Plesiosaurier aus dem Amaltheenton (Pliensbachium, Jura) von Bielefeld. 

Geologie und Paläontologie in Westfalen 90: 67-68.

---Bereits in den frühen 1980er Jahren entdeckte der Hannoveraner Fossiliensammler Lothar Schulz ein unvollständiges Plesiosaurier-Skelett in der Amaltheenton-Formation (oberes Pliensbachium, Unterjura) der Tongrube Beukenhorst II im Bielefelder Stadtteil Jöllenbeck (Schubert 2018). Der Fund umfasst, nebst diversen Fragmenten, etwa 90 Einzelknochen. Unter diesen befindet sich ein unvollständiger Unterkiefer, Zähne, sowie Teilen der Wirbelsäule, der Gürtelknochen und der Extremitäten (Sachs & Keiter 2018). Der Jöllenbecker Plesiosaurier gelangte später in den Besitz von Siegfried Schubert, einem Sammler von Fossilien aus der Region Bielefeld. Im Jahr 2015 übergab Herr Schubert den Fund dem Naturkunde-Museum Bielefeld, wo er seitdem unter der Inventarnummer Namu ES/jl 36052 verwahrt wird.

Reassessment of the Styxosaurus snowii (Williston, 1890) holotype specimen and its implications for elasmosaurid plesiosaurian interrelationships

Sachs, S., Lindgren J. & Kear, B.P. (2018) Reassessment of the Styxosaurus snowii (Williston, 1890) holotype specimen and its implications for elasmosaurid plesiosaurian interrelationships. Alcheringa 42(4): 560-574. 

---The holotype (KUVP 1301) of Styxosaurus snowii—one of the earliest described elasmosaurid plesiosaurians—consists of a well-preserved cranium, mandible and articulated sequence of anterior–mid-series cervical vertebrae found in the lowermost Campanian strata of the Smoky Hill Chalk Member in the Niobrara Formation of Kansas, USA. This particular specimen has proven important for recent phylogenies of Elasmosauridae, and is integral to resulting definitions of the subfamily-level clade, Styxosaurinae. Despite this, KUVP 1301 has not been redescribed or figured in detail since its original taxonomic establishment. We, therefore, re-evaluated KUVP 1301 and assessed its phylogenetic implications. Several notable character states are pertinent for diagnosing S. snowii at genus and species level: (1) an anisodont functional dentition comprising enlarged premaxillary and dentary teeth with a pair of maxillary ‘fangs’, and elongate posterior-most dentary teeth that overlap the upper tooth row; (2) a prominent dorsomedian crest extending from the tip of the premaxillary rostrum, and expanding into a low ‘mound-like’ boss between the external bony nasal openings and orbits; (3) a pronounced convex projection on the posterolateral edge of the squamosals; and (4) platycoelous post-axial cervical vertebral centra that are substantially longer than high, and bear both lateral longitudinal ridges and ventral notches. Character state comparisons with the congeneric subfamily specifier Styxosaurus browni suggest that taxonomic distinction is possible, but equivocal. We, therefore, restrict our definition of Styxosaurus to morphologies observable in KUVP 1301. Furthermore, phylogenetic analysis of our first-hand data returns inconsistent elasmosaurid intra-clade relationships, especially with regard to Styxosaurinae. Consequently, we posit that a more targeted reassessment of Elasmosauridae is necessary to resolve both species-level topologies and higher taxonomy within the group. 

First evidence of a large predatory plesiosaurian from the Lower Cretaceous non-marine ‘Wealden facies’ deposits of northwestern Germany

Sachs, S., Hornung, J.J., Lallensack, J. & Kear, B.P. (2018) First evidence of a large predatory plesiosaurian from the Lower Cretaceous non-marine ‘Wealden facies’ deposits of northwestern Germany. Alcheringa 42(4): 501-508. 

---Here, we describe the incomplete mandible of a large-skulled ‘pliosauromorph’ plesiosaurian from the Lower Cretaceous (Berriasian) of northwestern Germany. The fossil derives from limnic–brackish ‘Wealden facies’ deposits of the Deister Formation (Bückeberg Group), and is preserved as a natural mould in fine-grained sandstone. Examination of the original remains, in conjunction with a three-dimensional photogrammetrically digitized ‘cast’, revealed a conspicuous rosette of symphyseal alveoli, which would otherwise typically characterize Early–Middle Jurassic macrophagous plesiosaurians including rhomaleosaurids and the pliosaurid Simolestes. The Deister Formation ‘pliosauromorph’ represents the first record of a large-bodied plesiosaurian macrocarnivore from the ‘Wealden-facies’ strata of Europe, and thus adds a previously unrecognized trophic level of aquatic apex predators to the Early Cretaceous non-marine ecosystems of Europe. 

A rare new Pliensbachian plesiosaurian from the Amaltheenton Formation of Bielefeld in northwestern Germany

Sachs, S. & Kear, B.P. (2018) A rare new Pliensbachian plesiosaurian from the Amaltheenton Formation of Bielefeld in northwestern Germany. Alcheringa 42(4): 487-500.

---We describe a new plesiosaurian from the upper Pliensbachian Amaltheenton Formation of Bielefeld in northwestern Germany. The taxon is based upon an incomplete associated skeleton comprising part of the right mandibular ramus, several teeth, a series of cervical, pectoral, dorsal and caudal vertebrae, as well as ribs, limb girdle elements including a nearly complete right scapula, and various distal limb bones. A unique character state combination serves to distinguish the Amaltheenton Formation remains from other previously documented Early Jurassic plesiosaurians. The most important features are the presence of a longitudinal notch incising the posterior rim of the glenoid fossa and retroarticular process, and a pronounced ventrolateral shelf on the scapula, both of which constitute derived states otherwise shared with Early Cretaceous leptocleidians. However, phylogenetic analysis using a ‘total group’ Plesiosauria data-set that specifically accommodates for Pliensbachian taxa unanimously placed the Amaltheenton Formation plesiosaurian among Early–Middle Jurassic pliosaurids. This discovery is significant because it reveals unexpected homoplasy, but also because it establishes what is only the third formally named plesiosaurian taxon thus far documented from Pliensbachian strata worldwide. 

Soft-tissue evidence for homeothermy and crypsis in a Jurassic ichthyosaur

Lindgren, J., Sjövall, P., Thiel, V., Zheng, W., Ito, S., Wakamatsu, K., Hauff, R., Kear, B.P., Engdahl, A., Alwmark, C., Eriksson, M.E., Jarenmark, M., Sachs, S., Ahlberg, P.E., Marone, F., Kuriyama, T., Gustafsson, O., Malmberg, P., Thomen, A., Rodríguez-Meizoso, I., Uvdal, P., Ojika, M. & Schweitzer, M.H. (2018) Soft-tissue evidence for homeothermy and crypsis in a Jurassic ichthyosaur. Nature 564: 359–365.

---Ichthyosaurs are extinct marine reptiles that display a notable external similarity to modern toothed whales. Here we show that this resemblance is more than skin deep. We apply a multidisciplinary experimental approach to characterize the cellular and molecular composition of integumental tissues in an exceptionally preserved specimen of the Early Jurassic ichthyosaur Stenopterygius. Our analyses recovered still-flexible remnants of the original scaleless skin, which comprises morphologically distinct epidermal and dermal layers. These are underlain by insulating blubber that would have augmented streamlining, buoyancy and homeothermy. Additionally, we identify endogenous proteinaceous and lipid constituents, together with keratinocytes and branched melanophores that contain eumelanin pigment. Distributional variation of melanophores across the body suggests countershading, possibly enhanced by physiological adjustments of colour to enable photoprotection, concealment and/or thermoregulation. Convergence of ichthyosaurs with extant marine amniotes thus extends to the ultrastructural and molecular levels, reflecting the omnipresent constraints of their shared adaptation to pelagic life. 

Not worth mentioning? Paleontological collections of small museums: the example of Bielefeld (North Rhine Westphalia, Germany).

Keiter, M. & Sachs, S. (2018) Not worth mentioning? Paleontological collections of small museums: the example of Bielefeld (North Rhine Westphalia, Germany). In: Beck, L.A., & Joger, U (eds.) Palaeontological collections of Germany, Austria and Switzerland. Springer, Berlin: 69-76.

---The Naturkunde-Museum in Bielefeld (Germany) is one of the smaller Museums of Nature in Germany, but it harbors a large collection of paleontological specimens. This collection mainly comprises material from the region, and as such is a valuable local archive for the history of life and environment. Among the highlights are several holotypes of Mesozoic vertebrates and invertebrates, a valuable assemblage of fossils from the Oligocene Doberg locality, as well as Pleistocene vertebrate material. It is any museum’s responsibility to take care of and develop such a historical heritage and convey its worth to the public. 

Thalattosuchian remains from the late Aalenian Eisensandstein Formation of Baden-Württemberg, southwestern Germany

Abel, P., Sachs, S. & Young, M. T. (2018) Thalattosuchian remains from the late Aalenian Eisensandstein Formation of Baden-Württemberg, southwestern Germany. Geobonn 2018, Abstracts: 223.

---The fossil record of marine reptiles from the Aalenian is globally poor. In Germany they are mostly limited to isolated and fragmentary remains, although at least one ichthyosaur, Stenopterygius aaleniensis, is known from a complete and articulated skeleton. The Aalenian thalattosuchian record has not yet been studied in detail, and a number of specimens are still undescribed. Among these unpublished fossils is cranial and postcranial material from the late Aalenian Eisensandstein Formation (“Dogger β”) of Baden-Württemberg (SW Germany) that is housed at the Staatliches Museum für Naturkunde Stuttgart. Despite their fragmentary nature, this material can be attributed to both major thalattosuchian subclades, Teleosauroidea and Metriorhynchoidea. The teleosauroid material includes five incomplete rostra, one dorsal and two caudal vertebrae. Metriorhynchoids are represented by a fragmentary dentary and an isolated postorbital. Most specimens derive from localities in Aalen-Wasseralfingen and they are preserved in an iron oolite matrix. The same region yielded historical material of which some was described in the 1840s as Glaphyrorhynchus aalensis. These specimens, which were held in the collection of Graf zu Münster, appear to be lost and the validity of Glaphyrorhynchus, which was one of the first described thalattosuchians from Germany, cannot be confirmed. The material from the Eisensandstein Formation forms part of an ongoing projec to describe the Aalenian thalattosuchian record of Germany. Although only fragments are preserved, their study enhances our knowledge of Thalattosuchia – particularly helping to close some stratigraphic gaps in their fossil record. Furthermore, the material offers new insight into the late Aalenian marine ecosystems.

Einblicke in die Evolution der Thalattosuchier - Meereskrokodile des Mesozoikums

Young, M.T., Sachs, S. & Abel, P. (2018) Einblicke in die Evolution der Thalattosuchier - Meereskrokodile des Mesozoikums. Fossilien 3/2018: 16-23. 

---Die Gruppe der Crocodylomorpha, die alle heutigen Krokodile und deren ausgestorbene Verwandte umfasst, hat eine lange, abwechslungsreiche Evolution hinter sich. Ihre ältesten Vertreter aus der Späten Trias (vor ca. 237 Millionen Jahren) waren noch reine Landbewohner, deren Körperbau eher Windhunden als heutigen Krokodilen glich.

Mosasaurid and plesiosaurian remains from marginal facies of the lower Campanian (Upper Cretaceous) Bottrop and Vaals formations of western Germany

Sachs, S., Hornung, J. & Scheer, U. (2018) Mosasaurid and plesiosaurian remains from marginal facies of the lower Campanian (Upper Cretaceous) Bottrop and Vaals formations of western Germany. Cretaceous Research 87: 358-367. 

---Isolated remains of mosasaurids and plesiosaurians are recorded from the lower Campanian Bottrop and Vaals formations of North Rhine-Westphalia, western Germany. A tooth crown from Bottrop- Fuhlenbrock, referred to an elasmosaurid plesiosaurian, represents the first record of this group from late-Upper Cretaceous strata of the area. Another presumed plesiosaurian remain is a fragmentary gastralium from Duisburg-Walsum. Some of the mosasaurid material from the Bottrop Formation (a tooth crown and vertebrae from Bottrop-Fuhlenbrock and Duisburg-Walsum) is assigned to the subfamily Plioplatecarpinae. The Vaals Formation, which is a lateral equivalent of the Bottrop Formation, yielded a single tooth crown, found at Aachen-Bildchen, that is here referred to the genus Hainosaurus. These finds from the Bottrop and Vaals formations constitute evidence of the presence of these taxa in proximal shelf to nearshore settings during the Campanian. The mosasaurid occurrences in particular may be an indicator that diversity and abundance increased in more basinward facies and greater palaeowaterdepth. 

Fossil Focus: Thalattosuchia

Young, M. T., Sachs, S. & Abel, P. (2018) Fossil Focus: Thalattosuchia. Palaeontology Online 8(5): 1-13.

---To most people, crocodilians are large-bodied carnivores that have been unchanged since the age of the dinosaurs. However, during their 230 million-year history, modern crocodilians and their extinct relatives evolved a stunning diversity of body plans, with many looking very different from those alive today (crocodi les, alligators, caimans and gharials).

Arminisaurus schuberti – Ein neuer Plesiosaurier aus dem oberen Pliensbachium von Bielefeld und die Methoden seiner Konservierung

Sachs, S. & Keiter, M. (2018) Arminisaurus schuberti – Ein neuer Plesiosaurier aus dem oberen Pliensbachium von Bielefeld und die Methoden seiner Konservierung. Der Steinkern 32: 50-58.

---Verglichen mit den anderen Stufen des Unterjura sind Funde von Reptilien im Pliensbachium (182,7– 190,8 Mio. J.) eher selten (Sachs & Kear, 2017), weshalb ihre taxonomische Diversität für diesen Zeitabschnitt nur zum Teil bekannt ist. In der Literatur wird daher zuweilen von der “Pliensbachium-Lücke” gesprochen (Bardet et al., 2008). Dies gilt auch für die Gruppe der Plesiosaurier. Von diesen Meeresreptilien sind speziell aus dem nachfolgenden Toarcium eine große Zahl verschiedener Arten bekannt (Sachs et al., 2016; Vincent et al., 2017) und es liegen diverse, teils vollständige Skelette vor. Man denke etwa an die Funde aus der Region um Holzmaden (Hauff & Hauff, 1981) oder Whitby (Lomax, 2011).

Turonian marine amniotes from the Opole area in southwest Poland

Sachs, S., Jagt, J.W.M., Niedźwiedzki, R., Kędzierski, M., Jagt-Yazykova, E. & Kear, B.P. (2018) Turonian marine amniotes from the Opole area in southwest Poland. Cretaceous Research 84: 578-587. 

---A few isolated plesiosaurian and mosasauroid squamate teeth were collected from the Opole area in southwest Poland during the late nineteenth century. Calcareous nannofossil analysis of their associated rock matrix indicates an early Turonian age (nannofossil zone UC7; Mytiloides ex gr. labiatus and Inoceramus apicalis inoceramid zones), which is significant because this constitutes a globally enigmatic interval of marine amniote evolution. The Opole plesiosaurian teeth are attributable to polycotylids, but an indeterminate mesopodial was also recovered. They are similar to specimens from the Cenomanian–Turonian in the Saxonian Cretaceous Basin of Germany and the Chalk succession of England, but differ from polycotylid remains found in the coeval Bohemian Cretaceous Basin of the Czech Republic, which are far more robust. The mosasaurid tooth crown from Opole compares favourably with dentary and maxillary teeth of a number of Turonian yaguarasaurines and basal russellosaurines, but in having well-developed carinae and a smooth labial and strongly folded/markedly striated lingual tooth surfaces it can be differentiated from taxa such as Yaguarasaurus columbianus (Colombia), Romeosaurus fumanensis and R. sorbinii (both Italy) and ‘Mosasaurus’ gracilis (England). However, a single record from the Bohemian Cretaceous Basin may refer to a conspecific form. All this suggests a potential for slight compositional differences between Cenomanian–Turonian marine amniote assemblages across central and northern Europe, although otherwise these regions probably constituted a common faunal belt bordering the Tethys Ocean.

2017

The dentition of Megacephalosaurus eulerti (Plesiosauria, Pliosauridae) from the Turonian of Kansas and comments on the phylogenetic relationships of the last brachauchenines

Madzia, D., Sachs, S. & Lindgren, J. (2017) The dentition of Megacephalosaurus eulerti (Plesiosauria, Pliosauridae) from the Turonian of Kansas and comments on the phylogenetic relationships of the last brachauchenines. The Palaeontological Association, Abstracts of Annual Meeting, London: 93.

---Megacephalosaurus eulerti was a large brachauchenine pliosaurid that roamed the Western Interior Seaway during the middle Turonian (Late Cretaceous). The type specimen (FHSM VP-321) consists of a nearly complete skull including the dentaries, and associated incomplete postcranial material. We assessed the dental morphology of Megacephalosaurus and the variability observed in its dentition. The results show that the dentition of M. eulerti was subisodont and subhomodont, with the most apparent differences observed in the development of the apicobasal ridges, which branch in some teeth. However, the taxonomic utility of this feature is debatable and perhaps depends on the part of the tooth crown where it develops. We further revised the cranial anatomy of the taxon, which allowed for a reassessment of some of its morphological characters used in recent phylogenetic studies. Our parsimony analyses inferred a single unambiguous synapomorphy uniting the node comprising mid- to Late Cretaceous brachauchenines (presence of conical teeth with a subcircular cross-sectional shape). The latest brachauchenines (Brachauchenius and Megacephalosaurus) can be also roughly characterized by reduction of their maxillary tooth count and, perhaps, a switch from anisodont to subisodont dentition. However, the phylogenetic relationships remain somewhat elusive and would probably improve following modifications in data sampling.

Reste eines Elasmosauriers aus der Oberkreide von Schleswig-Holstein in der Sammlung des Naturkunde-Museums Bielefeld

Sachs, S. & Ladwig, J. (2017) Reste eines Elasmosauriers aus der Oberkreide von Schleswig-Holstein in der Sammlung des Naturkunde-Museums Bielefeld. Berichte Naturwissenschaftlicher Verein für Bielefeld und Umgegend 55: 28-36.

---Im Sommer 2016 erhielt das Naturkunde-Museum Bielefeld diverse Reste eines Elasmosauriers aus dem Obercampanium von Kronsmoor (Kreis Steinburg) in Schleswig-Holstein. Das Material umfasst fragmentarische Wirbel und Phalangen sowie nicht näher bestimmbare Fragmente. Weitere Teile des gleichen Skeletts (ein Zahn, Cervical-, Dorsal-und Caudalwirbel, Teile der Gliedmaßen und 110 Gastrolithen) befinden sich in der Sammlung des Geologischen Instituts der Universität Hamburg sowie in Privatsammlungen.

Reptilienfunde aus dem Muschelkalk von Gogolin

Sachs, S. & Hornung, J.J. (2017) Reptilienfunde aus dem Muschelkalk von Gogolin. In: Scheer, U. & Stottrop, U. (eds) Erdgeschichten. Geologie im Ruhr Museum. Verlag der Buchhandlung Walther König, Essen: 140-141.

---Das Ruhr Museum besitzt in seinen Sammlungsbeständen einige Reptilienfunde aus dem Muschelkalk von Gogolin in Oberschlesien (heute Gmina Gogolin, Polen). Zu diesen gehört das hier gezeigte Kieferfragment, das die charakteristische abgeflachte und robuste Bezahnung der Placodontier aufweist, welche der Gruppe ihren deutschen Namen Pflasterzahnsaurier einbrachte. Placodontier waren im Wasser lebende Reptilien, deren kräftige Zähne dazu dienten die Schalen ihrer Nahrung zu knacken, die wahrscheinlich aus Muscheln und Armfüßern bestand (Neenan, 2014). Die flachen „Pflasterzähne“ saßen sowohl im seitlichen Bereich der Kiefer, als auch auf dem Gaumen. Placodontier sind bisher nur aus der Triaszeit bekannt und brachten eine Reihe von verschiedenen Körperformen hervor. Einige Arten erinnern an die heutigen Galapagos-Meerechsen, andere mit ihrer Gestalt und dem Panzer aus Knochenplatten eher an Meeresschildkröten. Die meisten Placodontier wurden etwa 1 oder 2 m lang. Sie gehören in die weitere Verwandtschaft der Schuppenkriechtiere (Echsen und Schlangen), haben aber keine lebenden Verwandten mehr. Gogolin gehört zu den klassischen Fundstellen für Muschelkalkfossilien und lieferte auch schon früh Wirbeltierfossilien. So berichtete bereits Hermann von Meyer, der Vater der Wirbelpaläontologie in Deutschland, in seiner Monographie „Die Saurier des Muschelkalkes mit Rücksicht auf die Saurier aus dem bunten Sandstein und Keuper“ (Meyer, 1847-1855) von Reptilienfunden aus dem Gogoliner Raum. Später erforschten zum Beispiel Georg Gürich aus Breslau und Anton Schrammen aus Hildesheim weiteres Material (Gürich, 1884; Schrammen, 1899). Nebst Gogolin selbst sind auch andere Fundorten in Oberschlesien für Muschelkalkfossilien bekannt, so zum Beispiel Chorzów (Königshütte), Krapkowice (Krappitz), Zakrzów (Sakrau/Sacrau) oder Tarnowskie Góry (Tarnowitz).

A new basal elasmosaurid (Sauropterygia: Plesiosauria) from the Lower Cretaceous of Germany

Sachs, S., Hornung, J. J. & Kear, B. P. (2017) A new basal elasmosaurid (Sauropterygia: Plesiosauria) from the Lower Cretaceous of Germany. Journal of Vertebrate Paleontology 37(4): e1301945.

---Here we report on a new basal elasmosaurid plesiosaurian, Lagenanectes richterae, gen. et sp. nov., from the Lower Cretaceous (probably Upper Hauterivian) of Germany. The material includes a partial skull (cranium and mandible), the atlas-axis complex, additional cervical vertebrae, caudal vertebrae, an ilium, and limb elements. The basioccipital and atlas intercentrum are pathologically deformed, probably due to an osteomyelitic infection. Two potential autapomorphies were found in the mandible: (1) the alveolar margin at the symphysis is laterally expanded with the rostral-most alveoli being markedly procumbent and situated along the lateral margins of the dentaries; and (2) the ventral midline at the symphysis is produced into a prominent wedge-shaped platform indented by numerous irregular pits. Lagenanectes richterae, gen. et sp. nov., also shows a number of typical elasmosaurid traits, including a longitudinal lateral ridge on the cervical vertebral centra (although a ventral notch is absent) and teeth with oval cross-sections. Lagenanectes richterae, gen. et sp. nov., is one of the best-preserved plesiosaurians from the Lower Cretaceous of Europe.

On the largest Ichthyosaurus: A new specimen of Ichthyosaurus somersetensis containing an embryo

Lomax, D. & Sachs, S. (2017) On the largest Ichthyosaurus: A new specimen of Ichthyosaurus somersetensis containing an embryo. Acta Palaeontologica Polonica 62(3): 575-584.

---A formerly undescribed Ichthyosaurus specimen from the collection of the Niedersächsisches Landesmuseum (Lower Saxony State Museum) in Hannover, Germany, provides valuable new information. The skeleton was collected from the Lower Jurassic strata (lower Hettangian, Blue Lias Formation) of Doniford Bay, Somerset, UK. However, the specimen is a composite as almost the entire tail has been added and other parts are reconstructed. Regardless of the incomplete preservation, the estimated total length of this individual, based on the skull and precaudal length, is between 300 and 330 cm and it is thus the largest unequivocal example of the genus Ichthyosaurus. Cranial and postcranial characters, specifically from the maxilla, lacrimal, jugal, the humerus, and the ilium justify a referral to I. somersetensis. A fork-like shape of the proximal end of the ilium is unusual and has not been reported for any species of Ichthyosaurus. Likewise the presence of four elements in the third row of the hindfin, indicated by the presence of a bifurcation is novel for the species and has wider implications for the taxonomic utility of hindfins within the genus. The specimen also bears an embryo, which is only the third embryo known for Ichthyosaurus and the first to be positively identified to species level.

Pliosauromorph plesiosaurian remains from the Late Cretaceous of northwestern Germany

Sachs, S., Bertling, M. & Kear, B.P. (2017) Pliosauromorph plesiosaurian remains from the Late Cretaceous of northwestern Germany. In: 15th Annual Meeting of the European Association of Vertebrate Palaeontologists Munich, Germany. Zitteliana 91: 78-79.

---Plesiosaurian skeletal remains are rare in Late Cretaceous strata of Europe. During several years in the 1950`s, various cranial and postcranial elements of a pliosauromorph plesiosaurian had been collected by amateurs at Anröchte, North Rhine-Westphalia, northwestern Germany. They were donated to the Geomuseum of the WWU, Münster, but remained unstudied over decades: their softness combined with the embedment in a hard siliceous rock precluded preparation until suitable techniques were developed. These remains represent the most complete plesiosaurian reptile find from Turonian strata in Europe, but they have only been studied provisionally as yet. The material comes from the Soest Greensand Member (Salder Formation) of Late Turonian age. Included are elements of the skull and lower jaw, isolated teeth, vertebrae, a scapula, an ilium and limb elements. The teeth are robust and conical, bearing prominent enamel ridges on the surface of the crown. The cervicals are amphicoelous. Characteristics at the propodials include a facet for a supernumerary epipodial at the humerus and femur as well as a massive, dome-shaped capitulum at the femur. The robust, conical teeth and the massive rostrum demonstrate that the Anröchte plesiosaurian was a pliosauromorph and an apex predator in its environment.

Reappraisal of the ʽDorking Specimen’: An Upper Cretaceous brachauchenine pliosaurid from England

Madzia, D., Sachs, S., Evans, M., Lindgren, J., Kear, B.P. & Cau, A. (2017) Reappraisal of the ʽDorking Specimen’: An Upper Cretaceous brachauchenine pliosaurid from England. In: 15th Annual Meeting of the European Association of Vertebrate Palaeontologists Munich, Germany. Zitteliana 91: 55-56.

---Brachauchenine pliosaurids were marine macropredatory reptiles that might have been the only evolutionary lineage of pliosaurid plesiosaurians that crossed the Jurassic-Cretaceous boundary. Yet progress in understanding their origins and phylogenetic relationships has been hindered by limited knowledge of Early Cretaceous brachauchenine pliosaurid diversity and disparity relative to Late Cretaceous members of the clade. Late Cretaceous brachauchenines currently include only three valid taxa: Brachauchenius lucasi and Megacephalosaurus eulerti, initially described from the Turonian of Kansas, as well as ʽPolyptychodonʼ hudsoni from the Turonian of Texas. In Europe, the clade has long been represented by the widely distributed taxon Polyptychodon interruptus. However, recent reappraisal of the original type material of Polyptychodon from the mid-Cretaceous of England has shown that P. interruptus lacks diagnostic features, prompting a revision of all available specimens attributed to this classic taxon. Arguably the most complete is a partial cranium from the Cenomanian–middle Turonian of Dorking, England. This has been dubbed the ʽDorking specimen’, and was first described in 1860 by Sir Richard Owen, who referred it to Polyptychodon interruptus. Its historical association has also subsequently prompted suggestions that the specimen be designated the neotype of P. interruptus. Though incomplete, its morphology allows for comparisons with other brachauchenines, suggesting its potentially distinct nature. The phylogenetic placement of the specimen further supports the affinity with other Late Cretaceous brachauchenine pliosaurids, which clearly occupied apex-predator niches in marine ecosystems (including those of Europe) up until the end of the Turonian.

Redescription of the elasmosaurid plesiosaurian Libonectes atlasense from the Upper Cretaceous of Morocco

Sachs, S. & Kear, B.P. (2017) Redescription of the elasmosaurid plesiosaurian Libonectes atlasense from the Upper Cretaceous of Morocco. Cretaceous Research 74: 205-222. 

---The holotype of Libonectes atlasense is an almost complete skeleton from Upper Cretaceous (mid-Turonian) rocks of the Goulmima area in eastern Morocco. Initial assessment of this specimen in 2005 proposed generic referral based on stratigraphical contemporaneity with Libonectes morgani from the Cenomanian–Turonian of Texas, U.S.A. Nevertheless, relative differences in the profile of the premaxillary-maxillary tooth row, position of the external bony nasal opening, number of teeth and rostral inclination of the mandibular symphysis, proportions of the axial neural arch, and number of cervical and pectoral vertebrae were used to distinguish between these species. As part of an on-going comparative appraisal of elasmosaurid plesiosaurian osteo-anatomy, we re-examined the type and formally referred material of both L. atlasense and L. morgani in order to establish species validity, as well as compile a comparative atlas for use in future works. Our inspections revealed that these reportedly distinct species-level fossils are in fact virtually indistinguishable in gross morphology. Indeed, the only substantial difference occurs in relative prominence of the midline keel along the mandibular symphysis, which might be explained by intraspecific variation. Furthermore, our observations permit an amendment to the published generic diagnosis of Libonectes with the confirmation of important states such as the likely presence of a pectoral bar, distocaudal expansion of the humerus, and an epipodial foramen. In addition, novel features include a prominent ‘prong-like’ ventral midline process on the coracoids, and the development of a median pelvic bar that encloses a central fenestration. The composite remains of L. morgani thus constitute one of the most complete elasmosaurid skeletal hypodigms documented worldwide, and evidence a trans-Atlantic distribution for this apparently dispersive species during the early–Late Cretaceous. 

Cenomanian–Turonian marine amniote remains from the Saxonian Cretaceous Basin of Germany

Sachs, S., Wilmsen, M., Knüppe, J., Hornung, J. & Kear, B.P. (2017) Cenomanian–Turonian marine amniote remains from the Saxonian Cretaceous Basin of Germany. Geological Magazine 154(2): 237-246. 

---The Saxonian Cretaceous Basin constitutes an important source of rare Late Cretaceous marine amniote fossils from Germany. It is also historically famous, having been documented in a series of monographic works published by the distinguished German palaeontologist Hanns Bruno Geinitz in the nineteenth century. The most productive rock units include the upper Cenomanian Dölzschen Formation and upper Turonian Strehlen and Weinböhla limestones (lower Strehlen Formation). A survey of curated specimens recovered from these deposits has now identified isolated teeth of probable polycotylid and elasmosaurid plesiosaurians, as well as several humeri that are referred to protostegid marine turtles. The Saxonian Cretaceous Basin formed a continuous epeiric seaway with the Bohemian Cretaceous Basin during late Cenomanian – Turonian time. A western connection to the North Sea Basin also existed via the North German and Münsterland Cretaceous basins. The Mesozoic marine amniote remains from these regions therefore record a coeval northern European fauna that was probably homogeneous across the northern peri-Tethyan margin during Late Cretaceous time. 

2016

Kreide-Fossilien in Sachsen. Teil 15. Reptilien / Reptiles

Sachs, S.; Hornung, J. J.; Knüppe, J.; Wilmsen, M. & Kear, B.P. (2016) 15. Reptilien / 15. Reptiles. In: Niebuhr, B.; Wilmsen, M. (eds.) Kreide-Fossilien in Sachsen, Teil 2. Geologica Saxonica 62: 169-179.

---Reptilien gehören in der sächsischen Kreide (Elbtal-Gruppe) zu den Seltenheiten. Die wenigen bekannten Reste sind historische Funde, die erstmals im 19. Jahrhundert von Hanns Bruno Geinitz bearbeitet wurden. Sie stammen aus zwei stratigraphischen Einheiten, der Dölzschen-Formation (oberes Obercenomanium) sowie dem Strehlener und Weinböhlaer Kalk der unteren Strehlen-Formation (mittleres Oberturonium) und wurden fast ausschließlich im heutigen Stadtgebiet von Dresden gesammelt. Die Exemplare aus der Dölzschen-Formation sind sehr fragmentarisch erhalten und konnten keiner Gruppe mit Sicherheit zugeordnet werden. Das Material aus dem Strehlener Kalk hingegen zeigt, dass zwei Plesiosaurier-Familien (Elasmosauridae und ?Polycotylidae) sowie verschiedene marine Schildkröten der Familie Protostegidae im sächsischen Kreidebecken vorkamen. Hinweise auf Squamaten (Mosasauridae und Dolichosauridae), wie von Geinitz (1875a) postuliert, fehlen hingegen.

Reappraisal of Europe’s most complete Early Cretaceous plesiosaurian: Brancasaurus brancai Wegner, 1914 from the “Wealden facies” of Germany

Sachs, S., Hornung, J.J. & Kear, B.P. (2016) Reappraisal of Europe’s most complete Early Cretaceous plesiosaurian: Brancasaurus brancai Wegner, 1914 from the “Wealden facies” of Germany. PeerJ 4: 5745.

---The holotype of Brancasaurus brancai is one of the most historically famous and anatomically complete Early Cretaceous plesiosaurian fossils. It derived from the Gerdemann & Co. brickworks clay pit near Gronau (Westfalen) in North Rhine-Westphalia, northwestern Germany. Stratigraphically this locality formed part of the classic European ''Wealden facies,'' but is now more formally attributed to the uppermost strata of the Bückeberg Group (upper Berriasian). Since its initial description in 1914, the type skeleton of B. brancai has suffered damage both during, and after WWII. Sadly, these mishaps have resulted in the loss of substantial information, in particular many structures of the cranium and limb girdles, which are today only evidenced from published text and/or illustrations. This non-confirmable data has, however, proven crucial for determining the relationships of B. brancai within Plesiosauria: either as an early long-necked elasmosaurid, or a member of the controversial Early Cretaceous leptocleidid radiation. To evaluate these competing hypotheses and compile an updated osteological compendium, we undertook a comprehensive examination of the holotype as it is now preserved, and also assessed other Bückeberg Group plesiosaurian fossils to establish a morphological hypodigm. Phylogenetic simulations using the most species-rich datasets of Early Cretaceous plesiosaurians incorporating revised scores for B. brancai, together with a second recently named Bückeberg Group plesiosaurian Gronausaurus wegneri (Hampe, 2013), demonstrated that referral of these taxa to Leptocleididae was not unanimous, and that the topological stability of this clade is tenuous. In addition, the trait combinations manifested by B. brancai and G. wegneri were virtually identical. We therefore conclude that these monotypic individuals are ontogenetic morphs and G. wegneri is a junior synonym of B. brancai. Finally, anomalies detected in the diagnostic features for other ``Wealden'' plesiosaurians have prompted reconsiderations of interspecies homology versus intraspecific variability. We therefore propose that the still unresolved taxonomy of B. brancai should emphasize only those character states evident in the examinable fossil material, and specifically accommodate for growth-related modifications delimited via osteologically mature referred specimens.

Cyclotosaurus buechneri – ein neuer Riesenlurch aus der oberen Trias von Bielefeld

Witzmann, F., Sachs, S. & Nyhuis, C. (2016) Cyclotosaurus buechneri – ein neuer Riesenlurch aus der oberen Trias von Bielefeld. Der Steinkern 27: 46-51.

---

Mehrere Meter große, entfernt an Krokodile erinnernde Lurche, die sogenannten Capitosaurier, beherrschten in der Trias die limnischen Ökosysteme in weiten Teilen der Welt. Ein Vertreter der Capitosaurier, der aufgrund seiner rundum geschlossenen Ohröffnung zu den Rundohrlurchen (Cyclotosaurier) gezählt werden kann, wurde vor über 40 Jahren im Schilfsandstein der oberen Trias von Bielefeld entdeckt – ein Novum für Norddeutschland, findet man die Überreste solcher Riesen doch zumeist in triassischen Sedimenten Süddeutschlands. Der Fund wurde jetzt erstmals wissenschaftlich ausgewertet und es zeigte sich, dass es sich um eine neue Art der Gattung Cyclotosaurus handelt.

Protostegid marine turtle remains from the Cenomanian (Late Cretaceous) of the Kassenberg (Mülheim an der Ruhr, Western Germany)

Sachs, S., Scheer, U. & Rabi, M. (2016) Reste von protostegiden Meeresschildkröten aus dem Cenomanium (Oberkreide) des Kassenberges (Mülheim an der Ruhr, Westdeutschland / Protostegid marine turtle remains from the Cenomanian (Late Cretaceous) of the Kassenberg (Mülheim an der Ruhr, Western Germany). Berichte Naturwissenschaftlicher Verein für Bielefeld und Umgegend 54: 32-43.

---Postcranial remains of protostegid turtles from the lowermost Cenomanian of Mülheim an der Ruhr (Western Germany) are described. The material includes fragments from the carapace and appendicular skeleton of a taxon with a medium carapace length of approximately 20-30 cm. The turtle remains supplement the record of this group from the Cenomanian of Germany and the fossil fauna of the Kassenberg.

Big-headed marine crocodyliforms and why we must be cautious when using extant species as body length proxies for long-extinct relatives

Young, M., Rabi, M., Bell, M., Foffa, D., Steel, L., Sachs, S. & Peyer, K. (2016) Big-headed marine crocodyliforms and why we must be cautious when using extant species as body length proxies for long-extinct relatives. Palaeontologia Electronica 19.3.(30A:): 1-14.

---Body size is commonly used as a key variable for estimating ecomorphological trends at a macroevolutionary scale, making reliable body length estimates of fossil taxa critically important. Crocodylomorphs (extant crocodylians and their extinct relatives) evolved numerous 'aberrant' body-plans during their ~230 million-year history, ranging from ‘hooved’ terrestrial species to dolphin-like pelagic species. Such clades evolved distinct cranial and femoral scaling ratios (compared to total body length), thereby making extant taxa unsuitable proxies for estimating their body lengths. Here we illustrate that the fossil clade Teleosauridae also fits into this category. Teleosaurids were a predominately shallow marine clade that had a global distribution during the Jurassic. Known to have evolved a wide range of body lengths (2–5 m based on complete skeletons), there is currently no way of reliably estimating the size of incomplete specimens. This is surprising, as some teleosaurids have been considered very large (9–10 m in total length), thus making Teleosauridae the largest bodied clade during the first 100 million years of crocodylomorph evolution. Our examination and regression analyses of the best preserved teleosaurid skeletons demonstrates that: they were smaller than previously thought, with no known specimen exceeding 7.2 m in length; and that they had proportionally large skulls, and proportionally short femora, when compared to body length. Therefore, while many teleosaurid species evolved a cranial length of ≥1 m, these taxa would not necessarily have been larger than species living today. We advise caution when estimating body length for extinct taxa, especially for those outside of the crown group.

Overview of Marine Reptiles from the Turonian of the Opole area, southwest Poland

Sachs, S., Niedźwiedzki, R., Kędzierski, M., Kear, B.P., Jagt-Yazykova, E. & Jagt, J.W.M. (2016) Overview of Marine Reptiles from the Turonian of the Opole area, southwest Poland. XIV Annual Meeting of the European Association of Vertebrate Palaeontologist: 80.

---Turonian strata in the Opole area are well known for their well-preserved invertebrate fossils. Amongst the earliest descriptions is Leonhard’s 1897 monograph “Die Fauna der Kreideformation in Oberschlesien”, in which some isolated tetrapod elements, including mosasauroid and plesiosaurian teeth as well as a fragmentary bone named Plesiosauridarum were listed. Part of Leonhard's material is now curated in the collection of the Department of Paleozoology of University of Wrocław. Further, yet undescribed, specimens were found in the collection of the Ruhrmuseum in Essen. At present several plesiosaurian teeth, one mosasauroid tooth and a paddle element (? a plesiosaurian mesopodial) are available. Leonhard assigned the first-named to Polyptychodon interruptus. These are slender, yet conical with strong apicobasal striations, which justify reference to pliosauromorph plesiosaurians. They differ from typically more massive teeth of Late Cretaceous pliosaurids (Brachauchenius/Megacephalosaurus) and those found in coeval strata of the Bohemian Cretaceous Basin (BCB, Czech Republic) and more closely resemble teeth of polycotylids. Interestingly, a similar tooth has recently been described from Turonian strata of the Saxonian Cretaceous Basin (SCB, Germany). So far, mosasauroids are unknown from the SCB; however, a tethysaurine mosasauroid was described from the BCB. A recurved mosasauroid tooth crown, assigned to Liodon anceps by Leonhard (along with a second one tooth that could not be reloacted) shows well-developed carinae, strong lingual folds and finer ornament adapically and a near-smooth labial side with faint facetting. A comparison with coeval, or slightly younger, material from England is needed to assign this material to a genus, or family. Leonhard’s mysterious Plesiosauridarum could not be relocated, yet on the basis of his description and illustration, it can be identified as a damaged mosasauroid vertebra.

5th Triennial Mosasaur Meeting – a global perspective on Mesozoic marine amniotes. Abstracts and Program

Kear, B.P., Lindgren, J. & Sachs, S. (eds) (2016) 5th Triennial Mosasaur Meeting – a global perspective on Mesozoic marine amniotes. Abstracts and Program: 49 p.

Evidence for a Simolestes-like plesiosaurian from the Berriasian (Lower Cretaceous) limnic-brackish Bückeberg group of northwestern Germany

Sachs, S., Hornung, J.J., Lallensack, J. & Kear, B.P. (2016) Evidence for a Simolestes-like plesiosaurian from the Berriasian (Lower Cretaceous) limnic-brackish Bückeberg group of northwestern Germany. In: Sachs, S., Kear, B.P. & Lindgren (eds) 5th Triennial Mosasaur Meeting – a global perspective on Mesozoic marine amniotes. Abstracts and Program: 35-37.

---The middle to late Berriasian Bückeberg Group of northwestern Germany has yielded a number of plesiosaurian fossils. These include Europe's most complete Lower Cretaceous plesiosaurian, Brancasaurus brancai, in the fine grained, argillaceous Isterberg Formation near Gronau in Westfalen. Recently a second taxon, Gronausaurus wegneri was identified from the same locality and stratum (Hampe 2013) A higher diversity in the Bückeberg Group plesiosaurian assemblage is indicated by pliosauromorph and other plesiosaurian vertebrae from strata in the upper part of the sequence (see e.g. Koken 1896; Hornung et al., 2013), and both vertebrae and rib components described as Plesiosaurus degenhardti, from sandstones of the more marginal Deister Formation near Obernkirchen, Lower Saxony (Koken 1896). The only plesiosaurian cranial remains thus far documented from the Bückeberg Group were with the holotype specimens of B. brancai, and G. wegneri. These collectively characterize the classical "plesiosauromorph" morphology of a comparatively small head, long neck and slender conical teeth. Here we report on a newly discovered incomplete mandible representing a large-skulled, macrophagous plesiosaurian found within the coarse-grained nearshore facies from the Deister Formation of the Bückeberge range, probably near Obernkirchen. 

Re-description of Thalassomedon haningtoni – an elasmosaurid from the Cenomanian of North America

Sachs, S., Kear, B.P. & Lindgren, J. (2016) Re-description of Thalassomedon haningtoni – an elasmosaurid from the Cenomanian of North America. In: Sachs, S., Kear, B.P. & Lindgren (eds) 5th Triennial Mosasaur Meeting – a global perspective on Mesozoic marine amniotes. Abstracts and Program: 38-40.

---Thalassomedon haningtoni is one of the most thoroughly documented elasmosaurids. The type specimen, a nearly complete skeleton representing an osteologically mature individual with a well preserved postcranium (but damaged skull) was found in Cenomanian strata of the Graneros Shale in Colorado, USA. The only comprehensive description of this specimen produced so far is that of Welles (1943); however, his interpretations are contentious and require substantial updating relative to subsequent elasmosaurid discoveries. A second specimen of T. haningtoni is also known from the Cenomanian Graneros Shale of Nebraska, USA. This skeleton comprises a well preserved skull and articulated series of cervical, pectoral and a few dorsal vertebrae. Welles (1970) briefly mentioned the Nebraska T. haningtoni material in a newspaper article, and both Carpenter (1999) and Sato (2002) provided an interpretation of its skull. The osteologically immature elasmosaurid remains of Alzadasaurus riggsi, found likewise in Cenomanian strata of the Belle Fourche Formation in Montana, USA, was referred to T. haningtoni by Carpenter (1999); however, most of these remains are fragmentary and heavily distorted and they are insufficient for a confident diagnosis. It therefore cannot be referred to Thalassomedon with certainty and is best considered a nomen dubium.

A reassessment of historical plesiosaurian specimens from the Turonian (lower Upper Cretaceous) of the Opole area, southwest Poland

Sachs, S., Niedźwiedzki, R., Kędzierski, M., Kear, B.P., Jagt-Yazykova, E. & Jagt, J.W.M. (2016) A reassessment of historical plesiosaurian specimens from the Turonian (lower Upper Cretaceous) of the Opole area, southwest Poland. In: Sachs, S., Kear, B.P. & Lindgren (eds) 5th Triennial Mosasaur Meeting – a global perspective on Mesozoic marine amniotes. Abstracts and Program: 40-42.

---In 1897, Richard Leonhard presented brief descriptions and some illustrations of a few plesiosaurian remains (teeth and a supposed phalanx) from the lower Turonian of the Opole area (southwest Poland). Leonhard assigned the teeth to Polyptychodon interruptus and established a new genus, Plesiosauridarum (a species name was not supplied, making this a nomen nudum), for the supposed phalanx. Until recently, the whereabouts of all these specimens were unknown. However, during a recent survey of several Polish and German collections, most of Leonhard’s specimens could be relocated. Furthermore, other historical, still undescribed specimens (i.e., a tooth and paddle element) were encountered, and these supplement Leonhard’s material. Most of the original material has probably been found in now abandoned quarries in the area. Active quarrying is done at the Odra Nowa quarry in the Opole city area, but so far no plesiosaurian remains have been collected there. In total, four slender pliosauromorph teeth from the Opole area are available for study. These differ from the typically more massive teeth of Late Cretaceous pliosaurids (Brachauchenius/Megacephalosaurus) and the pliosauromorph teeth from coeval strata in the Bohemian Cretaceous Basin (Czech Republic; see Kear et al., 2014). However, a closely similar tooth crown has recently been described from the upper Turonian of the Saxonian Cretaceous Basin (eastern Germany; see Sachs et al., 2016). Generic placement of isolated pliosauromorph teeth from Cretaceous strata to the genus Polyptychodon is commonly seen in old literature sources.

Plesiosaurian fossils from Baltic glacial erratics: evidence of Early Jurassic marine amniotes from the southwestern margin of Fennoscandia

Sachs, S., Hornung, J. J. & Kear, B.P. (2016) Plesiosaurian fossils from Baltic glacial erratics: evidence of Early Jurassic marine amniotes from the southwestern margin of Fennoscandia. In: Kear, B.P., Lindgren, J., Hurum, J.H., Milán, J. & Vajda, V. (eds.) Mesozoic biotas of Scandinavia and its Arctic territories. Geological Society, London, Special Publications 434: 149-163.

---Early Jurassic plesiosaurian fossils are rare in the Scandinavian region, with a few isolated bones and teeth known from Bornholm, and anecdotal finds from East Greenland. The only other identifiable specimens derive from Toarcian-aged (based on ammonites) erratics deposited during Late Pleistocene glacial advances near the town of Ahrensburg, NE of Hamburg in northern Germany. The geographical source of these transported clasts is debated, but reconstructed ice-flow directions and lithofacies comparisons implicate either the offshore Baltic Sea between the Island of Bornholm and Mecklenburg–Vorpommern (Germany) or, less probably, south of the Danish Archipelago (Mecklenburg Bay). These regions collectively bordered the Fennoscandian landmass and adjacent Ringkøbing-Fyn Island in the late Early Jurassic, and were dominated by near-shore marine deltaic to basinal settings. The Ahrensburg plesiosaurian remains include postcranial elements reminiscent of both the microcleidid Seeleyosaurus and the rhomaelosaurid Meyerasaurus. These occur alongside other classic ‘Germanic province’ marine amniotes, such as the teleosaurid crocodyliform Steneosaurus and ichthyosaurian Stenopterygius cf. quadriscissus: thus, advocating faunal continuity between Scandinavia and southern Germany during the Toarcian, and a less pronounced marine reptile faunal provinciality than previously assumed. 

A partial plesiosaurian braincase from the Upper Cretaceous of Sweden

Sachs, S., Lindgren, J. & Siversson, M. (2016) A partial plesiosaurian braincase from the Upper Cretaceous of Sweden. In: Kear, B.P., Lindgren, J., Hurum, J.H., Milán, J. & Vajda, V. (eds.) Mesozoic biotas of Scandinavia and its Arctic territories. Geological Society, London, Special Publications 434: 293-301. 

---A partial exoccipital–opisthotic from the uppermost lower Campanian (Upper Cretaceous) of the Åsen locality, Kristianstad Basin, southernmost Sweden, is described and illustrated. The fossil represents the first braincase element of a plesiosaur found in Sweden. It includes the chamber for the ampulla and utriculus, openings for the caudal vertical and horizontal semicircular canals, and four foramina for cranial nerves. The incomplete braincase can be referred to an elasmosaurid plesiosaur, and closely resembles the exoccipital–opisthotic of Libonectes morgani and a referred specimen of Aristonectes parvidens. Although we discuss putative postcranial material of the elasmosaurid subfamily Aristonectinae in the uppermost lower Campanian of southernmost Sweden, the exoccipital–opisthotic from Åsen most likely belongs to a juvenile individual of a non-aristonectine elasmosaur. 

A new species of Cyclotosaurus (Stereospondyli, Capitosauria) from the Late Triassic of Bielefeld, NW Germany, and the intrarelationships of the genus

Witzmann, F., Sachs, S. & Nyhuis, C. (2016) A new species of Cyclotosaurus (Stereospondyli, Capitosauria) from the Late Triassic of Bielefeld, NW Germany, and the intrarelationships of the genus. Fossil Record 19(2): 83-100.

---A nearly complete dermal skull roof of a capitosaur stereospondyl with closed otic fenestrae from the middle Carnian Stuttgart Formation (Late Triassic) of Bielefeld-Sieker (NW Germany) is described. The specimen is assigned to the genus Cyclotosaurus based on the limited contribution of the frontal to the orbital margin via narrow lateral processes. A new species, Cyclotosaurus buechneri sp. nov., is erected based upon the following unique combination of characters: (1) the interorbital distance is short so that the orbitae are medially placed (shared with C. robustus); (2) the region lateral to the orbitae is only slightly broader than the orbitae (shared with C. posthumus, C. ebrachensis, C. intermedius, and C. mordax); (3) the postorbital region is slender (shared with C. ebrachensis); (4) the preorbital projection of the jugal is shorter than half the length of the snout (shared with C. mordax, C. ebrachensis, C. intermedius, C. posthumus, and C. hemprichi). A phylogenetic analysis of seven Cyclotosaurus species, including C. buechneri, and eight further capitosaur taxa with the Rhinesuchidae as an outgroup finds a monophyletic Cyclotosaurus. In accordance with its stratigraphic occurrence, C. buechneri nests at its base but is more derived than C. robustus. Among the more derived Cyclotosaurus species, C. ebrachensis and C. intermedius, as well as C. posthumus and C. hemprichi, form sister groups, respectively. However, the phylogenetic position of C. mordax with respect to both groups remains unresolved. In the phylogenetic analysis presented here, Cyclotosaurus is the sister group of the Heylerosaurinae (Eocyclotosaurus+Quasicyclotosaurus). Cyclotosaurus buechneri represents the only unequivocal evidence of Cyclotosaurus (and of a cyclotosaur in general) in northern Germany.

2015

Fossil Focus: Elasmosaurs

Sachs, S. & Kear, B.P. (2015) Fossil Focus: Elasmosaurs. Palaeontology Online, Volume 5, Article 2: 1-8.

---Elasmosaurs were a group of marine reptiles that lived during the Cretaceous period (about 145 million to 66 million years ago). They were fully adapted to an aquatic lifestyle, and had a distinctive body plan comprising a compact, streamlined body, long, paddle-like limbs and an extremely elongated neck with a large number of vertebrae (Fig. 1). The first named elasmosaur was Elasmosaurus platyurus from the Late Cretaceous (Campanian stage, about 83.6 million to 72.1 million years ago). It was found in Kansas and described by the famous US scientist Edward Drinker Cope (1840–97, Fig. 2), who, when he first wrote about it in 1868, believed that the almost complete series of 72 neck vertebrae came from a massively long tail. Today, many articulated skeletons of elasmosaurs provide insight in the anatomy, lifestyle and relationships of these spectacular ancient sea monsters.

Belege für riesige Pliosaurier aus dem Jura Deutschlands

Sachs, S. & Nyhuis, C. (2015) Belege für riesige Pliosaurier aus dem Jura Deutschlands. Der Steinkern 21: 74-82

---Pliosaurier gehören zu den größten Meeresreptilien, die je gelebt haben. Vom Mittleren Jura bis in die obere Unterkreide erreichten einige Gattungen gigantische Ausmaße und standen meist an der Spitze der Nahrungskette. In den letzten Jahren haben besonders zwei Pliosaurier-Funde das Interesse der Öffentlichkeit erregt. Einer davon ist als „Monster von Aramberri“ bekannt geworden. Es handelt sich dabei um ein unvollständiges Skelett aus dem Kimmeridgium von Mexiko, dessen fossile Überreste von Buchy et al. (2003) als nicht näher bestimmbarer Pliosauride beschrieben wurden. Das Tier erreichte vermutlich eine Gesamtlänge von 15 m. Der zweite populär gewordene Fund, gleichfalls ein unvollständiges Skelett, stammt aus dem Tithonium von Svalbard (Spitzbergen) und erhielt den Spitznamen „Predator X“. 

Megacnemus – a forgotten reptile, presumably from the Triassic of Poland

Skawiński, T.,Tałanda, M. & Sachs, S. (2015) Megacnemus – a forgotten reptile, presumably from the Triassic of Poland. In: J. Jagt, G. Hebda, S. Mitrus, E. Jagt-Yazykova, A. Bodzioch, D. Konietzko-Meier, K. Kardynał, K. Gruntmejer (ed.) EAVP. XIII Meeting Opole, Abstracts: 139.

---Protorosaurs were important components of many Permian and Triassic ecosystems. Some of the known protorosaurian taxa have been established on the basis of fragmentary material. One of these is Megacnemus grandis von Huene, 1954, of which only a single complete, yet distorted propodial – originally interpreted as a femur – is known. Although exact locality data are missing, von Huene (1954) pointed out that the specimen had most probably been found in the Middle Triassic deposits near Gogolin (southwest Poland). Since its initial description the genus Megacnemus has received very little attention. Our attempt is to redescribe the type specimen and assess the phylogenetic position of the taxon. The protorosaurian affinities of Megacnemus proposed by von Huene (1954) have been accepted in later publications; however, the bone differs from femora of most ‘traditional’ protorosaurs, such as Protorosaurus, Macrocnemus and tanystropheids, by its robustness and the lack of a sigmoidally curved shaft (however, the latter might have been affected by the distortion of the bone). Yet, Megacnemus does share some traits with the humeri and femora of Dinocephalosaurus from the Middle Triassic of China, and the humeri of Macrocnemus from the Middle Triassic of Italy, Switzerland and China.

A new basal elasmosaurid skeleton with joint pathologies from the Lower Cretaceous of Germany

Sachs, S., Hornung, J., Wohlsein, P. & Kear, B. (2015) A new basal elasmosaurid skeleton with joint pathologies from the Lower Cretaceous of Germany. In: J. Jagt, G. Hebda, S. Mitrus, E. Jagt-Yazykova, A. Bodzioch et al. (eds.) EAVP. XIII Meeting Opole, Abstracts: 131.

---The family Elasmosauridae constitutes one of the most iconic plesiosaurian clades. Their conservative body plan represents the popular model for Plesiosauria, and is characterised by a distinctive osteological morphology especially adapted for hyperelongation of the neck. Here we report on a new basal elasmosaurid from the Lower Cretaceous (upper Hauterivian) of Lower Saxony, northern Germany. The fossil comprises skeletal components from a n osteologically old individual: most of the cranium and partial mandible, the atlas axis complex, cervical and caudal vertebrae, ribs, an ilium and paddle elements. The specimen displays a number of primitive elasmosaurid traits including five premaxillar y teeth and amphicoelous craniad cervical centra that bear short lateral longitudinal ridges, but lack ventral notches on the articular faces. The dentaries are unusual in having extremely procumbent alveoli in the symphyseal region. The mandible also form s a prominent wedge shaped ventral platform. Interestingly, the articular surfaces of the basioccipital and atlas centrum show changes suggestive of a degenerative or chronic inflammatory joint disease. Irregular exostotic outgrowths adjacent to the articu lar surface are present similar to an osteophytic growth. These lesions may have caused impaired joint function and pain, perhaps contributing to the death of the individual.

Marine tetrapods from the Middle Jurassic (Aalenian and Bajocian) of Bielefeld (northwest Germany)

Sachs, S. & Hornung, J. J. (2015) Marine Tetrapoden aus dem Mittleren Jura (Aalenium und Bajocium) von Bielefeld (Nordwestdeutschland) / Marine tetrapods from the Middle Jurassic (Aalenian and Bajocian) of Bielefeld (northwest Germany). Berichte Naturwissenschaftlicher Verein für Bielefeld und Umgegend 53: 52-73.

---Hitherto unpublished marine tetrapod remains from the Upper Aalenian (Ludwigienton-Formation) and Upper Bajocian (Parkinsonienton-Formation) of Bielefeld-Bethel are described. Both stratigraphic intervals contain remains of thalattosuchians, ichthyosaurians and plesiosaurians, which indicate the persistence of faunal assemblages similar to those from distal basinal settings of the Lower Jurassic into the Middle Jurassic. This is of special importance since marine tetrapod remains are generally rare in the Aalenian and Bajocian of Central Europe. The strata containing both assemblages were deposited under transgessive to highstand systems tract conditions.

Postcranium of the paradigm elasmosaurid plesiosaurian Libonectes morgani (Welles, 1949)

Sachs, S. & Kear, B.P. (2015) Postcranium of the paradigm elasmosaurid plesiosaurian Libonectes morgani (Welles, 1949). Geological Magazine 152(4): 694-710.

---Elasmosauridae constitutes one of the most immediately recognizable plesiosaurian radiations. Their distinctive body plan represents the popular model for Plesiosauria, and is typified by an osteological morphology especially adapted for hyper-elongation of the neck. Nevertheless, many archetypal elasmosaurids are known only from incomplete and/or inadequately documented material, a problem that has contributed to their uncertain intra-clade relationships. A prime example of this is Libonectes morgani from the Upper Cretaceous of Texas, USA, which is frequently presented as an elasmosaurid structural proxy because of its three-dimensionally preserved holotype skull. Perplexingly though, both the taxonomic diagnosis and phylogenetic placement of L. morgani rely primarily upon the cervical vertebrae, together with the pectoral girdle and forelimb, yet most of these elements are now lost and figured only as line drawings. We therefore reviewed the remnant postcranial skeleton of L. morgani first-hand with the objective of clarifying its defining character states. Our observations showed that the existing diagnosis of L. morgani is indeed inadequate. Moreover, the only identifiable autapomorphies occurred within the axial skeleton. This concurred with an examination of character scores used in published plesiosaurian phylogenies, and highlights the persistent significance of postcranial elements for discriminating elasmosaurid taxa. 

Mosasaurs from Germany – a brief history of the first 100 years of research

Sachs, S., Hornung, J.J. & Reich, M. (2015) Mosasaurs from Germany – a brief history of the first 100 years of research. Netherlands Journal of Geosciences – Geologie en Mijnbouw 94(1): 5-18.

---In Germany, mosasaur remains are very rare and only incompletely known. However, the earliest records date back to the 1830s, when tooth crowns were found in the chalk of the Isle of Rügen. A number of prominent figures in German palaeontology and geosciences of the 19th and 20th centuries focused on these remains, including, among others, Friedrich von Hagenow, Hermann von Meyer, Andreas Wagner, Hanns Bruno Geinitz and Josef Pompeckj. Most of these works were only short notes, given the scant material. However, the discovery of fragmentary cranial remains in Westphalia in 1908. This theory saw the existence of continuous lines of descent, evolving in parallel, and did not regard higher taxonomic units as monophyletic groups but as intermediate paraphyletic stages of evolution. In this idea, nearly all fossil taxa form part of these lineages, which extend into the present time, and natural extinction occurs very rarely, if ever. In Steinmann’s concept, mosasaurs were not closely related to squamates but formed an intermediate member in a anagenetic chain from Triassic thalattosaurs to extant baleen whales. The newly found specimen led Josef Pompeckj to write a vehement rebuttal to Steinmann’s theory, published in 1910, showing that his conclusions were conjectural and speculative, being based on convergence and not supported by scientific evidence. This particular specimen, housed in Göttingen, later also inspired a piece of palaeoart by Franz Roubal under the instructions of Othenio Abel.

2014

Note on a new plesiosaur (Reptilia: Sauropterygia) skeleton from the upper Pliensbachian (Lower Jurassic) of Bielefeld, northwest Germany

Sachs, S., Schubert, S., Kear, B.P. (2014) Mitteilung über ein neues Skelett eines Plesiosauriers (Reptilia: Sauropterygia) aus dem Oberen Pliensbachium (Unterjura) von Bielefeld, Nordwestdeutschland / Note on a new plesiosaur (Reptilia: Sauropterygia) skeleton from the upper Pliensbachian (Lower Jurassic) of Bielefeld, northwest Germany. Berichte Naturwissenschaftlicher Verein für Bielefeld und Umgegend 52: 26-35.

---This note briefly introduces a new plesiosaur specimen from the upper Pliensbachian (Lower Jurassic) of Bielefeld-Jöllenbeck (North Rhine-Westphalia, NW Germany). The skeleton comprises a partial skull, sections of the vertebral column, ribs and components of the pectoral girdle and limbs. It belonged to an immature individual of 2-3 m length. Important diagnostic features include a prominent notch in the caudal border of the mandibular fossa glenoidalis, craniad cervical centra that are higher than long, a pair of foramina subcentralia on the cervicals separated by a broad ventral keel, and a dorsal process on the scapula that bears a gently convex cranial margin, but no pronounced medial thickening. The Bielefeld specimen is one of the most complete plesiosaurs currently known from the Pliensbachian and differs from the coeval European taxa Westphaliasaurus and Cryonectes, but shows some similarity to unpublished material from the Pliensbachian of England. The Bielefeld plesiosaur indicates that a substantial diversity of taxa was present in European marine systems during the Pliensbachian stage.

Ein gepanzerter Dinosaurier aus der Unterkreide Westfalens

Sachs, S. & Hornung J. J. (2014) Ein gepanzerter Dinosaurier aus der Unterkreide Westfalens. Der Steinkern 18(3): 29-36.

---Die Tongrube Gerdemann bei Gronau (Westfalen) zählt zu den bedeutendsten historischen Fundpunkten für Wirbeltierfossilien aus der Unteren Kreide in Deutschland. Aus diesem Aufschluss werden zwei Knochen vorgestellt, die sich in der Sammlung der Universität Münster bzw. der Ausstellung des Drilandmuseums in Gronau befinden und dort lange ein wenig beachtetes Dasein fristeten. Die wissenschaftliche Untersuchung zeigte jüngst, dass es sich um Knochen von Ankylosauriern handelt, deren Vorkommen in Deutschland bis dato noch nicht sicher belegt war. 

Meeresreptilien vom Südpol der Unterkreide

Sachs, S. & Kear, B.P. (2014) Meeresreptilien vom Südpol der Unterkreide. Fossilien 3/2014: 16-22.

---Während der späten Unterkreide (Aptium, Albium) war das Gebiet des heutigen Australiens noch mit der Antarktis vereint. Die gemeinsame Landmasse befand sich in der Nähe des damaligen Südpols; die Wassertemperaturen fielen zum Teil unter den Gefrierpunkt. Dennoch lebte dort eine artenreiche Fauna, die unter anderem marine Reptilien wie Ichthyosaurier und Plesiosaurier umfasste. Sie waren offensichtlich an diese kalten Temperaturen angepasst. Vielleicht besaßen sie einen hohen Körperfettanteil, führten saisonale Wanderungen durch oder hatten einen erhöhten Stoffwechsel.

2013

Sauropterygian fossils from the predominantly limnic–brackish Bückeberg Formation (Berriasian–Early Valanginian, Early Cretaceous) of northwestern Germany – diversity, distribution, and palaeoecology

Hornung, J.J., Sachs, S. & Kear, B.P. (2013) Sauropterygian fossils from the predominantly limnic–brackish Bückeberg Formation (Berriasian–Early Valanginian, Early Cretaceous) of northwestern Germany – diversity, distribution, and palaeoecology. In: Reitner, Yang, Wang & Reich (eds.) Palaeobiology and Geobiology of Fossil Lagerstätten through Earth History: 75.

---The Bückeberg Formation (Lower Saxony Basin, northern Germany and eastern Netherlands) represents a siliciclastic succession, deposited during the mid-Berriasian through to the earliest Valanginian. The unit is predominantly lacustrine with fluvial inflow and episodic marine connections to the Boreal Sea. Its fossil faunas include sauropterygian remains comprising isolated bones and partial, articulated skeletons. Though most of these finds cannot be identified at genus level, there is evidence of at least three morphotypes, representing distinct taxa: “Plesiosaurus degenhardti” Koken, 1887; Brancasaurus brancai Wegner, 1914; and an unnamed “pliosauromorph”. Other previously named taxa are dubious and/or may be synonymous. Articulated remains are concentrated to two abundance maxima in the Bückeberg Formation: the Obernkirchen Sandstone (lower Bückeberg Fm.) and Osterwald Mbr. (upper Bückeberg Fm.). The depositional environments of the former succession comprise freshwater lacustrine-deltaic barrier and mouthbar sandstones, and brackish deep-water pelites and littoral marls/calcarenites in the latter. The largely complete skeletons of B. brancai originate from a deep-water Konservat-Lagerstätte formed under brackish, euxinic conditions. These individuals are osteologically immature, which accords with other occurrences of limnic plesiosaurs and might infer ontogenetically controlled, migratorial behaviour.

Revised vertebral count in the ‘‘longest-necked vertebrate’’ Elasmosaurus platyurus Cope 1868, and clarification of the cervical-dorsal transition in Plesiosauria

Sachs, S., Kear, B.P. & Everhart, M. (2013) Revised vertebral count in the ‘‘longest-necked vertebrate’’ Elasmosaurus platyurus Cope 1868, and clarification of the cervical-dorsal transition in Plesiosauria. PLoS ONE 8(8): e70877.

---Elasmosaurid plesiosaurians are renowned for their immensely long necks, and indeed, possessed the highest number of cervical vertebrae for any known vertebrate. Historically, the largest count has been attributed to the iconic Elasmosaurus platyurus from the Late Cretaceous of Kansas, but estimates for the total neck series in this taxon have varied between published reports. Accurately determining the number of vertebral centra vis-à-vis the maximum length of the neck in plesiosaurians has significant implications for phylogenetic character designations, as well as the inconsistent terminology applied to some osteological structures. With these issues in mind, we reassessed the holotype of E. platyurus as a model for standardizing the debated cervical-dorsal transition in plesiosaurians, and during this procedure, documented a “lost” cervical centrum. Our revision also advocates retention of the term “pectorals” to describe the usually three or more distinctive vertebrae close to the cranial margin of the forelimb girdle that bear a functional rib facet transected by the neurocentral suture, and thus conjointly formed by both the parapophysis on the centrum body and diapophysis from the neural arch (irrespective of rib length). This morphology is unambiguously distinguishable from standard cervicals, in which the functional rib facet is borne exclusively on the centrum, and dorsals in which the rib articulation is situated above the neurocentral suture and functionally borne only by the transverse process of the neural arch. Given these easily distinguishable definitions, the maximum number of neck vertebrae preserved in E. platyurus is 72; this is only three vertebrae shorter than the recently described Albertonectes, which together with E. platyurus constitute the “longest necked” animals ever to have lived.

Cenomanian-Turonian mosasauroids from the Bohemian Cretaceous Basin

Kear, B.P., Sachs, S., Ekrt, P. & Hornung, J.J. (2013) Cenomanian-Turonian mosasauroids from the Bohemian Cretaceous Basin. In: Polcyn, M.J. & Jacobs, L.L. (eds) 4th Triennial International Mosasaur Meeting. Program and Abstracts. Dallas, Texas: 24.

---The Bohemian Cretaceous Basin (BCB) is an intracontinental depositional depression that extends from Brno in eastern Moravia, through Bohemia to the north and west of Prague, and across the Czech-German border into southern Saxony around Dresden. During the early Late Cretaceous, the BCB formed part of the continuous peri-Tethyan shelf of central and southern Europe, which was inundated by a northwesterly trending marine transgression extending between the Tethys Ocean and the Boreal North Sea Basin. Fossils of marine amniotes that inhabited this shallow epicontinental seaway have been documented for over 155 years, but have attracted little recent research attention in comparison to other more famous localities elsewhere. Despite this, a comprehensive reassessment of existing museum collections, together with new excavations, has identified a succession of diverse assemblages spanning the late Cenomanian through to Turonian-Coniacian boundary. Conspicuous amongst the remains are the isolated bones and teeth of primitive mosasauroids. The stratigraphically oldest of these specimens derive from the late Cenomanian Dölzschen Formation around Dresden in eastern Germany, and include small teeth and a bone fragment possibly representing the posterior condyle of a procoelous centrum.

Ankylosaur remains from the Early Cretaceous (Valanginian) of northwestern Germany

Sachs, S. & Hornung J. J. (2013) Ankylosaur Remains from the Early Cretaceous (Valanginian) of Northwestern Germany. PLoS ONE 8(4): e60571.

---A fragmentary cervico-pectoral lateral spine and partial humerus of an ankylosaur from the Early Cretaceous (early Valanginian) of Gronau in Westfalen, northwestern Germany, are described. The spine shows closest morphological similarities to the characteristic cervical and pectoral spines of Hylaeosaurus armatus from the late Valanginian of England. An extensive comparison of distal humeri among thyreophoran dinosaurs supports systematic differences in the morphology of the distal condyli between Ankylosauria and Stegosauria and a referral of the Gronau specimen to the former. The humerus fragment indicates a rather small individual, probably in the size range of H. armatus, and both specimens are determined herein as ?Hylaeosaurus sp.. A short overview of other purported ankylosaur material from the Berriasian-Valanginian of northwest Germany shows that, aside from  the material described herein, only tracks can be attributed to this clade with confidence at present.

2012

Eine Fährtenplatte mit Chirotherium barthii KAUP und cf. Rotodactylus aus dem Oberen Buntsandstein (Untere Trias) von Pirmasens

Haderer, F.-O. & Sachs, S. (2012) Eine Fährtenplatte mit Chirotherium barthii KAUP und cf. Rotodactylus aus dem Oberen Buntsandstein (Untere Trias) von Pirmasens. Mitteilungen der POLLICHIA 96: 5-10.

---Aus der Sammlung des Pfalzmuseums für Naturkunde – POLLICHIA-Museum in Bad Dürkheim wird eine Fährtenplatte aus dem Oberen Buntsandstein (Untere Trias) von Pirmasens beschrieben, auf welcher die Fährtenart Chirotherium barthii KAUP und ein weiterer Fährtenrest cf. Rotodactylus erhalten ist. Sowohl Chirotherium barthii KAUP als auch cf. Rotodactylus stellen die ersten Nachweise dieser Taxa aus Rheinland-Pfalz dar.

2011

Ein elasmosaurider Plesiosaurier aus dem unteren Campan (Oberkreide) von Sehnde-Höver (Landkreis Hannover)

Sachs, S. (2011) Ein elasmosaurider Plesiosaurier aus dem unteren Campan (Oberkreide) von Sehnde-Höver (Landkreis Hannover). Arbeitskreis Paläontologie Hannover 39. 12-19.

---In der Sammlung von Herrn Udo Frerichs (Langenhagen) befinden sich einige craniale Reste eines Elasmosauriers. Die Stücke wurden im Frühjahr 1978 in der Grube „Alemannia“ in Sehnde-Höver bei Hannover entdeckt (FRERICHS 1994, 2005, FRERICHS & FRERICHS 1978). Nebst gut erhaltenen Zähnen unterschiedlicher Größe umfasst das Fundgut Teile der Mandibula, sowie einige nicht näher bestimmbare Knochenreste.

2007

Book review: Everhart, M.J. 2005. Oceans of Kansas: A Natural History of the Western Interior Sea

Sachs, S. (2007) Book review: Everhart, M.J. 2005. Oceans of Kansas: A Natural History of the Western Interior Sea. – Bloomington, Indiana University Press. PalArch’s Journal of Vertebrate Palaeontology.

---Book review PalArch’s Journal of Vertebrate Palaeontology (2007) Everhart, M.J. 2005. Oceans of Kansas: A Natural History of the Western Interior Sea. – Bloomington, Indiana University Press Book review by S. Sachs Mike Everhart is Adjunct Curator of Paleontology at the Sternberg Museum of Natural History at FortHays State University and owner of the award winning homepage www.oceansofkansas.com. His book ‘Oceans of Kansas’ gives an overview of the Cretaceous of Kansas; including geology, taxonomy and history of the (mainly marine) fossils. The book is not a pure scientific book but rather written for the larger public; it has been named the featured book from Kansas for the National Book Festival in Washington, D.C. 

2006

First record of a mosasaur (Reptilia: Squamata) from the Upper Cretaceous of Central Germany

Sachs, S. (2006) First record of a mosasaur (Reptilia: Squamata) from the Upper Cretaceous of Central Germany. Abhandlungen und Berichte aus dem Museum Heineanum 7: 1-7.

---Two fragmentary bones, part of a left ilium and an anterior dorsal vertebra, of a mosasaur are described and discussed. They were collected from the Upper Cretaceous (Lower Campanian) Heimburg Formation in Blankenburg am Harz and represent the first record of this group in Central Germany.

Juvenile ornithopod (Dinosauria: Rhabdodontidae) remains from the Upper Cretaceous (Lower Campanian, Gosau Group) of Muthmannsdorf (Lower Austria)

Sachs, S. & Hornung, J.J. (2006) Juvenile ornithopod (Dinosauria: Rhabdodontidae) remains from the Upper Cretaceous (Lower Campanian, Gosau Group) of Muthmannsdorf (Lower Austria). Geobios 39: 415-425.

---

The fragmentary remains of a juvenile rhabdodontid ornithopod from the Coal-bearing Complex of the Gosau Group (Lower Campanian, Grünbach syncline) at Muthmannsdorf near Wiener Neustadt, Lower Austria are revised. The material, probably belonging to a single individual, includes a right dentary (lectotype of Iguanodon suessi Bunzel, 1871, designated herein), teeth, a fragmentary parietal, fragments of scapula, ?radius, femur, tibia, two vertebrae (lost) and a manual ungual. The lectotype dentary does not provide clear autapomorphies or sufficient diagnostic features to determine its position within the Rhabdodontidae at generic level. By this “Iguanodon suessi” Bunzel, 1871 and the genus “Mochlodon” Seeley, 1881, to which it was latter referred as type species, cannot be characterized sufficiently by differential diagnosis and these are best considered nomina dubia. Based upon combined character comparisons (mainly postcranial features) the Muthmannsdorf ornithopod is referred herein to Zalmoxes Weishampel, Jianu, Csiki and Norman, 2003, a genus so far known from the late Maastrichtian of Romania. It probably but not evidently represents a yet unnamed species, most closely related to Zalmoxes shqiperorum Weishampel, Jianu, Csiki and Norman, 2003. At the present state of knowledge the Austrian material is not further diagnostic at the species level and kept in open nomenclature as Zalmoxes sp.

2005

Redescription of Elasmosaurus platyurus Cope 1868 (Plesiosauria: Elasmosauridae) from the Upper Cretaceous (lower Campanian) of Kansas, USA

Sachs, S. (2005) Redescription of Elasmosaurus platyurus Cope 1868 (Plesiosauria: Elasmosauridae) from the Upper Cretaceous (lower Campanian) of Kansas, USA. Paludicola 5(3): 92-106.

---The type specimen of Elasmosaurus platyurus Cope, 1868 from the Upper Cretaceous (lower Campanian) of Kansas, U.S.A. is redescribed. It consists of part of the skull (e. g., both premaxillae, parts of the maxillae, the occipital condyle and parts of the dentaries), the almost complete vertebral column, including the atlas-axis complex, as well as the pectoral and pelvic girdles (although the latter are now lost). The genus Elasmosaurus can be defined by two unambiguous autapomorphies, the presence of six premaxillary teeth and the high number of 71 cervical vertebrae. It also exhibits a number of advanced features, which are discussed and compared with other elasmosaurs.

Remarks on the pectoral girdle of Hydrotherosaurus alexandrae (Plesiosauria: Elasmosauridae)

Sachs, S. (2005) Remarks on the pectoral girdle of Hydrotherosaurus alexandrae (Plesiosauria: Elasmosauridae). PalArch 4(1): 1-6.

---The pectoral girdle of Hydrotherosaurus alexandrae Welles 1943, an elasmosaurid plesiosaur from the Upper Cretaceous (Maastrichtian) of California, USA, is redescribed. Some differences to the reconstruction presented in the original description, as well as newly discovered features of the pectoral girdle are discussed and a new reconstruction is provided.

Tuarangisaurus australis sp. nov. (Plesiosauria: Elasmosauridae) from the Lower Cretaceous of Northeastern Queensland, with additional notes on the phylogeny of the Elasmosauridae

Sachs, S. (2005) Tuarangisaurus australis sp. nov. (Plesiosauria: Elasmosauridae) from the Lower Cretaceous of Northeastern Queensland, with additional notes on the phylogeny of the Elasmosauridae. Memoirs of the Queensland Museum 50(2): 425-440.

---The skull and associate cervical vertebrae of an elasmosaur from the Lower Cretaceous of northeastern Queensland are described as a new species of Tuarangisaurus, Tuarangisaurus australis. They represent the oldest record of that genus and the first secure outside New Zealand. A phylogenetic analysis based on 19 characters of the skull and cervical vertebrae is undertaken. One tree is presented, including all valid members of the Elasmosauridae for which sufficient cranial material is known. The results give an example for the interrelationship of the Elasmosauridae and show the probable position of Tuarangisaurus.

2004

Redescription of Woolungasaurus glendowerensis (Plesiosauria: Elasmosauridae) from the Lower Cretaceous of Northeast Queensland

Sachs, S. (2004) Redescription of Woolungasaurus glendowerensis (Plesiosauria: Elasmosauridae) from the Lower Cretaceous of Northeast Queensland. Memoirs of the Queensland Museum 49(2): 713-731.

---Woolungasaurus glendowerensis erected by PERSSON, 1960, was based on an incomplete postcranial skeleton, comprising cervical, pectoral, dorsal and caudal vertebrae, an almost complete sacrum, as well as elements of the pectoral and pelvic girdles and of the fore and hind paddles. Following comparisons with specimens referable to all valid genera of the Elasmosauridae, this specimen and additional material is identified as belonging to the genus Styxosaurus. It is the earliest record of this genus and the first in the Southern Hemisphere.

2003

Der Pionier der Wirbeltierpaläontologie C. E. Hermann von MEYER (1801-1869) und die Saurier der Pfalz

Hornung, J.J. & Sachs, S. (2003) Der Pionier der Wirbeltierpaläontologie C. E. Hermann von MEYER (1801-1869) und die Saurier der Pfalz. Pfälzer Heimat 54(4): 139-146.

---Der berühmte Paläontologe Hermann von MEYER (Abb.1), ein Pionier der Erforschung fossiler Wirbeltiere, der im Jahr 2001 seinen 200sten Geburtstag hatte, hinterließ Spuren seiner weitgefächerten Forschungsarbeiten auch in der Pfalz. Bereits 1844 berichtete er in einer brieflichen Mitteilung an Prof. Heinrich Georg BRONN über einen Skelettrest aus dem Rotliegend von Münsterappel (Abb. 2), welchen er später (MEYER 1848) unter dem Namen Apateon beschrieb. Dieses Fossil, sowie weitere Stücke aus der gleichen Zeitperiode behandelt v. MEYER einige Jahre später (1858) ausführlich in seiner Monographie „Reptilien aus der Steinkohleformation in Deutschland“. 

An ichthyosaur fragment from the Cretaceous of Northland, New Zealand

Sachs, S. & Grant-Mackie, J.A. (2003) An ichthyosaur fragment from the Cretaceous of Northland, New Zealand. Journal of the Royal Society of New Zealand 33(1): 307-314.

---The rostrum fragment of an ichthyosaur from Northland in New Zealand is described. The specimen appears to belong to the genus Platypterygius. It is the first Mesozoic marine vertebrate fossil reported from Northland and the first cranial element of a Cretaceous ichthyosaur from New Zealand. The fragment is, unfortunately, of uncertain provenance and could have come from the widespread Northland Allochthon (Early Cretaceous–Oligocene) or the allochthonous Houhora Complex (late Early Cretaceous) or Whatuwhiwhi Formation (latest Early to Late Cretaceous), perhaps by way of initial erivation from the Early Miocene Omapere Conglomerate. 

2001

Observations on the postcranial morphology, ontogeny and palaeobiology of Sclerocephalus haeuseri (Amphibia: Actinodontidae) from the Lower Permian of Southwest Germany

Lohmann, U. & Sachs, S. (2001) Observations on the postcranial morphology, ontogeny and palaeobiology of Sclerocephalus haeuseri (Amphibia: Actinodontidae) from the Lower Permian of Southwest Germany. Memoirs of the Queensland Museum 46(2): 771-781.

---The temnospondyl amphibian Sclerocephalus is described in four ontogenetic stages: larval, juvenile, adult and late adult. In particular the postcranial anatomy was observed. Some specimens preserve stomach contents, consisting of paramblypterid fishes and small amphibians (Micromelerpeton, Apateon). In one specimen, the remains of a small Sclerocephalus were found. Larval and juvenile individuals probably lived in a different habitat than adult and late adult ones. In the juvenile, adult and late adult stages, Sclerocephalus was the top predator in its environment.

Diplodocus - Ein Sauropode aus dem Oberen Jura (Morrison-Formation) Nordamerikas

Sachs, S. (2001) Diplodocus - Ein Sauropode aus dem Oberen Jura (Morrison-Formation) Nordamerikas. Natur und Museum 131(5): 133-154.

---Als größtes Schaustück im großen Lichthof des Senckenberg Museums befindet sich in dessen Mitte die 18 m lange Skelettmontage des Diplodocus (Abb. 1). Die Knochen gelangten 1907 nach Frankfurt; als Geschenk des New Yorker American Museum of Natural History zur Eröffnung des neuen Museums im jetzigen Gebäude (die Schausammlungen waren zuvor im Eschenheimer Turm untergebracht). So wurde es dann am Eröffnungstag, dem 13. Oktober 1907, von Morris K. JESUP, dem Präsidenten des American Museum of Natural History, feierlich der Senckenbergischen Naturforschenden Gesellschaft übergeben. Damit war Frankfurt die erste Stadt Europas, die das Skelett eines amerikanischen Dinosauriers zeigen konnte. Zugleich aber war der Diplodocus das einzige montierte Skelett dieser Art außerhalb der Vereinigten Staaten (DREVERMANN, 1907, 1911).

2000

Mosasaurier-Reste aus der Oberkreide von Nordrhein-Westfalen

Sachs, S. (2000) Mosasaurier-Reste aus der Oberkreide von Nordrhein-Westfalen. Geologie und Paläontologie in Westfalen 56: 35-44.

---Reste von Mosasauriern aus der Oberkreide (Campanium) von Nordrhein-Westfalen werden beschrieben. Bei diesem Material handelt es sich um ein Kieferfragment (Maxillare), Paddelelemente, Rippenfragmente und Wirbel. Das Maxillare konnte der Gattung Leiodon zugeordnet werden und wird als Leiodon cf. mosasauroides beschrieben.

Ein Pliosauride (Sauropterygia: Plesiosauria) aus der Oberkreide von Anröchte in Westfalen

Sachs, S. (2000) Ein Pliosauride (Sauropterygia: Plesiosauria) aus der Oberkreide von Anröchte in Westfalen. Geologie und Paläontologie in Westfalen 56: 25-33.

---In der Sammlung des Geologisch-Paläontologischen Museums der Westfälischen Wilhelms Universität in Münster wird der Skelettrest eines Plesiosauriers aufbewahrt, der aus dem mittleren Turon von Anröchte bei Lippstadt stammt. Über den Fundort und die Fundgeschichte liegen keine näheren Angaben vor. Der einzige Hinweis ist ein altes Etikett, auf dem die Realschule für Jungen und Mädchen in Anröchte als Eigentümer genannt ist. Der Fund besteht aus etwa 100 einzelnen Stücken. Bei den meisten Knochen sind, durch Witterungseinflüsse bedingt, keine Konturen mehr zu erkennen - ein Umstand, der eine Bestimmung erschwert oder ganz verhindert hat. 

1997

Placodus impressus - Fisch- und Placodontier (Pflasterzahnsaurier)-Zähne aus dem Buntsandstein von Zweibrücken (Pfalz)

Sachs, S. (1997) Placodus impressus - Fisch- und Placodontier (Pflasterzahnsaurier)-Zähne aus dem Buntsandstein von Zweibrücken (Pfalz). Mitteilungen der Pollichia 84: 15-18.

---Fünf Zähne aus dem oberen Buntsandstein von Zweibrücken werden von AGASSIZ (1833) als Placodus impressus beschrieben. Vier dieser Zähne sind dem placodonten Fisch Sargodon tomicus zugeordnet worden; ein Zahn stammt vermutlich von einem cyamodonten Placodontier. Es ist dies der früheste Beleg der Ordnung Placodontia.

Mesozoische Reptilien aus Nordrhein-Westfalen

Sachs, S. (1997) Mesozoische Reptilien aus Nordrhein-Westfalen. In: Sachs, S., Rauhut, O.W. & Weigert, A. (eds.) 1. Treffen der deutschsprachigen Paläoherpetologen: Düsseldorf 21. bis 23. Februar 1997; extended abstracts. Terra Nostra 97(7): 22-27.

---Fossil reptiles from the Mesozoic are rarities in Nordrhein-Westfalen (western Germany), and the majority of specimens found are only fragmentarily preserved. The first report of a fossil reptile, parts of a mosasaur skeleton from the Upper Cretaceous (Cenoman) of Schöppingen, was published by W. von der Marck already in 1858. Another mosasaur from Haldem (Senon) was described by Pompeckj (1910). Lommerzheim (1976) reported a nearly complete wing of an unidentified pterosaur from the Upper Cretaceous (Turon) of Dinslaken. The present repository of the poorly prepared remain is unknown. The Lower Cretaceous (Berriasian) clay-pit Gerdemann near Gronau yielded plesiosaurs, dinosaurs, and turtles.

1. Treffen der deutschsprachigen Paläoherpetologen: Düsseldorf 21. bis 23. Februar 1997; extended abstracts

Sachs, S., Rauhut, O.W. & Weigert, A. (eds.) (1997) 1. Treffen der deutschsprachigen Paläoherpetologen: Düsseldorf 21. bis 23. Februar 1997; extended abstracts. Terra Nostra 97(7), 38p.

---Content: Baszio, S. Taxonomische und Paläoökologische Untersuchungen an kanadischen Dinosaurier-Fundstellen. p. 3-4. Fastnacht, M. Neue Erkenntnisse zum Zahnwechsel der Flugsaurier. p. 5-6. Kraus, R. Kiefermechanik longorostriner Krokodile. p. 7-8. Maisch, M. & Hungerbühler, A. The temporal region of the gigantic Lower Jurassic ichthyosaur Temnodontosaurus throws new light on the cranial anatomy and origin of the Ichthyosauria. p. 9-13. Michelis, I. Taphonomie des Howe Quarrys; Bighorn Country, Wyoming, USA. p. 14-16. Rauhut, O. Zur Schädelanatomie von Shuvosaurus inexpectatus (Dinosauria, Theropoda). p. 17-21. Sachs, S. Mesozoische Reptilien aus Nordrhein-Westfalen. p. 22-27. Werner, C. & Zils, W. Tendaguru-Expedition Dezember 1996. p. 28-32. Windolf, R. Theropoden-Zähne aus dem Oberen Jura Niedersachsens. p. 33-34. Teilnehmerliste. p. 36-38. 

Erster Nachweis eines gepanzerten Dinosauriers (Reptilia, Ornithischia, Thyreophora) aus der Unterkreide (Berrias) von Gronau in Westfalen

Sachs, S. (1997) Erster Nachweis eines gepanzerten Dinosauriers (Reptilia, Ornithischia, Thyreophora) aus der Unterkreide (Berrias) von Gronau in Westfalen. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte 1997(1): 56-64.

---Das distale Ende eines rechten Humerus von einem thyreophoren Dinosaurier aus der unteren Kreide (oberes Berrias) der Tongrube Gerdemann in Gronau in Westfalen wird beschrieben und abgebildet. Der größere Condylus radialis, der eine laterale Abstufung erkennen läßt, und die geringe laterale Breite des Schaftes oberhalb der Gelenkfläche sind markante Merkmale von nodosauriden Dinosauriern.

1996

Ein Ichthyosaurier-Fund aus dem Dogger von Bielefeld

Sachs, S. & Hungerbühler, A. (1996) Ein Ichthyosaurier-Fund aus dem Dogger von Bielefeld. Bericht des naturwissenschaftlichen Vereins für Bielefeld und Umgegend 37: 255-260.

---Die unvollständigen Reste des Axialskeletts eines Ichthyosauriers aus dem mittleren Jura (Bathonium) von Bielefeld-Gadderbaum werden beschrieben und abgebildet. Das Stück befindet sich in der Schausammlung des Naturkunde-Museums in Bielefeld. Obwohl eine sichere Bestimmung nicht möglich ist, wird eine Zuordnung zu Ophthalmosaurus diskutiert.

Dinosaurier-Funde aus Westfalen

Sachs, S. (1996) Dinosaurier-Funde aus Westfalen. Bericht des naturwissenschaftlichen Vereins für Bielefeld und Umgegend 37: 237-253.

---Im Bundesland Nordrhein-Westfalen sind Dinosaurier-Reste nur von drei Lokalitäten im Landesteil Westfalen bekannt geworden; Brilon-Nehden, Gronau und Wallücke. Die größte Ausbeute lieferte Nehden mit über 1400 Einzelknochen, die sich im wesentlichen dem Ornithopoden Iguanodon zuordnen ließen, der mit zwei Arten vertreten war und hier auch erstmals im juvenilen Stadium nachgewiesen werden konnte. In Gronau wurden nur drei Dinosaurier-Knochen entdeckt. Ein Stück konnte als Humerus-Ende eines thyreophoren Dinosaurier, vermutlich eines Nodosauriden, bestimmt werden und stellt den ersten gesicherten Nachweis dieser Gruppe in Deutschland dar. Bei den beiden anderen Stücken handelt es sich um Wirbelkörper, die eventuell von Theropoden stammen könnten. Die in Wallücke gefundenen Stücke konnten einem Stegosaurier (Lexovisaurus) und einem Omithopoden (möglicherweise einem Dryosaurier) zugeordnet werden. Der Stegosaurier-Rest ist ein Stachelffagment und stellt den ersten Nachweis dieser Tiergruppe in Deutschland dar.

Ein großer Ichthyosaurier aus dem Pliensbachium von Bielefeld - Neue Einblicke in die Ichthyosaurier des Mittleren Lias und das Gebiß von Temnodontosaurus

Hungerbühler, A. & Sachs, S. (1996) Ein großer Ichthyosaurier aus dem Pliensbachium von Bielefeld - Neue Einblicke in die Ichthyosaurier des Mittleren Lias und das Gebiß von Temnodontosaurus. Bericht des naturwissenschaftlichen Vereins für Bielefeld und Umgegend 37: 15-52.

---Wir beschreiben hier das fragmentäre Skelett eines Ichthyosauriers von geschätzten acht Meter Länge aus dem Unteren Pliensbachium (davoei-Zone) von Bielefeld. Nach der Größe, massiven Schnauze, straken Bezahnung und weiterer Schädelmerkmale wird das Tier der Gattung Temnodontosaurus zugeordnet. Das Stück ist artlich nicht bestimmbar. Eine kritische Überprüfung der bisher beschriebenen Ichthyosauriertaxa erbibt, daß im mittleren Lias von Europa die Gattungen Leptonectes, Temnodontosaurus und Stenopterygius vorkommen. "Leptopterygius" nuertingensis v. HUENE, 1931, wird hier als einzige valide Art im Pliensbachium eingestuft, deren generische Zuordnung allerdings neu untersucht werden muß. Leptopterygius margaritatus v. HUENE, 1922 wird als Temnodontosaurus sp. angesehen und ein Lectotyp bestimmt. Wir geben weiterhin eine Übersicht der Taxonomie und Paläobiogeographie unterjurassischer Ichthyosaurier. Daraus läßt sich eine Tendenz zu verstärktem Provinzialismus der Ichthyosaurierfaunen im Laufe des Lias ableiten. Der Bielefelder Temnodontosaurus zeigt, daß zwischen den unter- und oberliassischen Temnodontosauriern eine geographische und zeitliche Kontinuität besteht. Wir postulieren, daß sich aus einfachen Kegelzähnen in der Ontogenese von Temnodontosaurus platyodon (CONYBEARE, 1822), T. eurycephalus Mc Gowan , 1974 und T. burgundiae (Gaudry , 1896) eine Bezahnung mit Schneidekanten entwickelt. Das Gebiß dieser drei Arten ist in diesem Wachstumsstadium heterodont mit bi- oder tricarinaten Zahnformen im hinteren Kieferabschnitt. Der Bielefelder Schädel besitzt im Gegensatz zu den anderen Temnodontosaurus-Arten auch im Alter keine Schneidekanten an den Zähnen.