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.

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.

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.

One of the major questions in evolutionary vertebrate morphology is the origin and meaning of temporal skull openings in land vertebrates. Partly or fully surrounded by bones, one, two, or even three openings may evolve behind the orbit, within the ancestrally fully roofed anapsid (scutal) skull. At least ten different morphotypes can be distinguished in tetrapods with many modifications and transitions in more crownward representatives. A number of potential factors driving the emergence and differentiation of temporal openings have been proposed in the literature, but only today are proper analytical tools available to conduct traceable tests for the functional morphology underlying temporal skull constructions. In the present study, we examined the anatomical network in the skull of one representative of early amniotes, †Captorhinus aguti, which ancestrally exhibits an anapsid skull. The resulting skull modularity revealed a complex partitioning of the temporal region indicating, in its intersections, the candidate positions for potential infratemporal openings. The framework of †C. aguti was then taken as a template to model a series of potential temporal skull morphotypes in order to understand how skull openings might influence the modular composition of the amniote skull in general. We show that the original pattern of skull modularity (†C. aguti) experiences comprehensive changes by introducing one or two temporal openings in different combinations and in different places. The resulting modules in each skull model are interpreted in regard to the feeding behavior of amniotes that exhibit(ed) the respective skull morphotypes. An important finding is the alternative incorporation of the jugal and palate to different modules enforcing the importance of an integrated view on skull evolution: the temporal region cannot be understood without considering palatal anatomy. Finally, we discuss how to better reconstruct relative jaw muscle compositions in fossils by considering the modularity of the skull network. These considerations might be relevant for future biomechanical studies on skull evolution.

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.

While most early limbed vertebrates possessed a fully-roofed dermatocranium in their temporal skull region, temporal fenestrae and excavations evolved independently at least twice in the earliest amniotes, with several different variations in shape and position of the openings. Yet, the specific drivers behind this evolution have been only barely understood. It has been mostly explained by adaptations of the feeding apparatus as a response to new functional demands in the terrestrial realm, including a rearrangement of the jaw musculature as well as changes in strain distribution. Temporal fenestrae have been retained in most extant amniotes but have also been lost again, notably in turtles. However, even turtles do not represent an optimal analog for the condition in the ancestral amniote, highlighting the necessity to examine Paleozoic fossil material. Here, we describe in detail the sutures in the dermatocranium of the Permian reptile Captorhinus aguti (Amniota, Captorhinidae) to illustrate bone integrity in an early non-fenestrated amniote skull. We reconstruct the jaw adductor musculature and discuss its relation to intracranial articulations and bone flexibility within the temporal region. Lastly, we examine whether the reconstructed cranial mechanics in C. aguti could be treated as a model for the ancestor of fenestrated amniotes. We show that C. aguti likely exhibited a reduced loading in the areas at the intersection of jugal, squamosal, and postorbital, as well as at the contact between parietal and postorbital. We argue that these “weak” areas are prone for the development of temporal openings and may be treated as the possible precursors for infratemporal and supratemporal fenestrae in early amniotes. These findings provide a good basis for future studies on other non-fenestrated taxa close to the amniote base, for example diadectomorphs or other non-diapsid reptiles.

The morphology of the temporal region in the tetrapod skull traditionally has been a widely discussed feature of vertebrate anatomy. The evolution of different temporal openings in Amniota (mammals, birds, and reptiles), Lissamphibia (frogs, salamanders, and caecilians), and several extinct tetrapod groups has sparked debates on the phylogenetic, developmental, and functional background of this region in the tetrapod skull. This led most famously to the erection of different amniote taxa based on the number and position of temporal fenestrae in their skulls. However, most of these taxa are no longer recognised to represent natural groupings and the morphology of the temporal region is not necessarily an adequate trait for use in the reconstruction of amniote phylogenies. Yet, new fossil finds, most notably of parareptiles and stem-turtles, as well as modern embryological and biomechanical studies continue to provide new insights into the morphological diversity of the temporal region. Here, we introduce a novel comprehensive classification scheme for the various temporal morphotypes in all Tetrapoda that is independent of phylogeny and previous terminology and may facilitate morphological comparisons in future studies. We then review the history of research on the temporal region in the tetrapod skull. We document how, from the early 19th century with the first recognition of differences in the temporal region to the first proposals of phylogenetic relationships and their assessment over the centuries, the phylogenetic perspective on the temporal region has developed, and we highlight the controversies that still remain. We also compare the different functional and developmental drivers proposed for the observed morphological diversity and how the effects of internal and external factors on the structure of the tetrapod skull have been interpreted.

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 handfulValanganian 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.

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 upper 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.

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-Wurttemberg, 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. Pascal Abel [pascal.abel@senckenberg.de], Senckenberg Center for Human Evolution and Palaeoenvironment, Eberhard-Karls-University Tubingen, Sigwartstrasse 10, 72076 Tubingen, Germany; Sven Sachs [sachs.pal@gmail.com], Naturkunde-Museum Bielefeld, Abteilung Geowissenschaften, Adenauerplatz 2, 33602 Bielefeld, Germany; Mark T. Young [marktyoung1984@gmail.com], School of GeoSciences, Grant Institute, University of Edinburgh, James Hutton Road, Edinburgh, EH9 3FE, UK.

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.

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. Mystriosaurus is diagnosed in having: a heavily and extensively ornamented skull; large and numerous neurovascular foramina on the premaxillae, maxillae and dentaries; anteriorly oriented external nares; and four teeth per premaxilla. Our phylogenetic analyses reveal M. laurillardi to be distantly related to Steneosaurus bollensis, supporting our contention that they are different taxa. Interestingly, our analyses hint that Mystriosaurus may be more closely related to the Chinese teleosauroid (previously known as Peipehsuchus) than any European form.

and Mallison, H. 2019. A new species of 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.

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.