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Allain, Ronan, Vullo, Romain, Rozada, Lee, Anquetin, Jérémy, Bourgeais, Renaud, Goedert, Jean, Lasseron, Maxime, Martin, Jeremy E., Pérez-García, Adán, Fabrègues, Claire Peyre De, Royo-Torres, Rafael, Augier, Dominique, Bailly, Gilles (2022): Vertebrate paleobiodiversity of the Early Cretaceous (Berriasian) Angeac-Charente Lagerstätte (southwestern France): implications for continental faunal turnover at the J/K boundary. Geodiversitas 44 (25): 683-752, DOI: 10.5252/geodiversitas2022v44a25

Theriosuchus sp. (Fig. 17 A-D) DESCRIPTION Small isolated teeth are commonly recovered from residues obtained from bulk screening. Many of them (Fig. 17 A-D) are leaf-shaped, labiolingually compressed, low-crowned and pseudoziphodont, a characteristic of the posterior dentition in the atoposaurid genus Theriosuchus (Schwarz & Salisbury 2005; Lauprasert et al. 2011; Martin et al. 2014b). Members of the genus Theriosuchus are small crocodyliforms with total body lengths less than 1m (Schwarz & Salisbury 2005). Besides teeth, two skull bones might belong to this genus: a right jugal (ANG 16-5179) and a fragmentary frontal (ANG 14-3692). The jugal is about 1 cm long and its ornamented lateral surface is thin and projects ventrally. The frontal preserves the interorbital area and displays an acute median keel on its dorsal surface. A finely sculpted osteoderm, longer than wide and possessing a shallow median keel (Fig.19D), matches the morphology of dorsal osteoderms of the tail region in Theriosuchus pusillus (Owen 1879; Clark 1986)., Published as part of Allain, Ronan, Vullo, Romain, Rozada, Lee, Anquetin, Jérémy, Bourgeais, Renaud, Goedert, Jean, Lasseron, Maxime, Martin, Jeremy E., Pérez-García, Adán, Fabrègues, Claire Peyre De, Royo-Torres, Rafael, Augier, Dominique & Bailly, Gilles, 2022, Vertebrate paleobiodiversity of the Early Cretaceous (Berriasian) Angeac-Charente Lagerstätte (southwestern France): implications for continental faunal turnover at the J / K boundary, pp. 683-752 in Geodiversitas 44 (25) on page 704, DOI: 10.5252/geodiversitas2022v44a25, http://zenodo.org/record/6902033, {"references":["SCHWARZ D. & SALISBURY S. W. 2005. - A new species of Theriosuchus (Atoposauridae, Crocodylomorpha) from the Late Jurassic (Kimmeridgian) of Guimarota, Portugal. Geobios 38: 779 - 802. https: // doi. org / 10.1016 / j. geobios. 2004.04.005","LAUPRASERT K., LAOJUMPON C., SAENPHALA W., CUNY G., THIRA- KUPT K. & SUTEETHORN V. 2011. - Atoposaurid crocodyliforms from the Khorat group of Thailand: first record of Theriosuchus from Southeast Asia. Palaontologische Zeitschrift 85: 37 - 47. https: // doi. org / 10.1007 / s 12542 - 010 - 0071 - z","MARTIN J. E., RABI M., CSIKI- SAVA Z. & VASILE S. 2014 b. - Cranial morphology of Theriosuchus sympiestodon (Mesoeucrocodylia, Atoposauridae) and the widespread occurrence of Theriosuchus in the Late Cretaceous of Europe. Journal of Paleontology 88 (3): 444 - 456. https: // doi. org / 10.1666 / 13 - 106","OWEN R. 1879. - On the association of dwarf crocodiles (Nannosuchus and Theriosuchus pusillus, eg) with the diminutive mammals of the Purbeck Shales. Quarterly Journal of the Geological Society 35: 148 - 155. https: // doi. org / 10.1144 / GSL. JGS. 1879.035.01 - 04.02","CLARK J. M. 1986. - Phylogenetic Relationships of the Crocodylomorph Archosaurs. Unpublished Ph. D, dissertation, University of Chicago, Chicago, 556 p."]}

International audience; The internal endocranial structures of an undescribed atoposaurid crocodylomorph from the Sao Khua Formation (Cretaceous: Berriasian-Barremian) in the North-East of Thailand are investigated. The specimen is comparable in size and external morphology to Theriosuchus grandinaris Lauprasert et al. 2011 but is preserved with the braincase uncrushed, contrary to the previously described holotype. We document for the first time the internal braincase structures in atoposaurids using synchrotron X-ray micro-computed tomography. The endocast of the braincase, associated nerves and arteries, auditory labyrinth, and cranial pneumatization, although quite deformed, are reconstructed at high resolution and compared to those of extant and fossil crocodylomorphs, representative of different ecological adaptations. This atoposaurid specimen shows an antero-posterior brain curvature and pericerebral spines (new structures), somewhat developed cerebral hemispheres, expanded semicircular canals with a more developed anterior one but an almost straight lateral one, a dorsoventrally expanded pituitary fossa, but also overdeveloped intertympanic diverticula and pharyngotympanic sinuses. The ecologicalsignificance of these structures is explored and, using different proxies and comparisons with extant taxa, we suggest that this specimen likely exhibited a downwardly tilted head posture (by about 10◦) and was sensitive to both low and mid frequencies. Functional comparisons are proposed between this specimen, extinct terrestrial crocodylomorphs (sebecosuchians), extant semi-aquatic crocodilians and aquatic (thalattosuchians) forms. From the morphology of the auditory labyrinth, we infer an enhanced sensitivity to pitching rather than yawing. Several hypotheses are formulated regarding the pneumatization of the skull. These features are discussed in ecological and phylogenetic frameworks. Our results highlight the need to gather new data, especially on altirostral forms, in order to deepen our understanding of the evolution of endocranial structures in crocodylomorphs with different ecological specializations, as well as to integrate them into new phylogenetic approaches.

International audience; A large number of fossil-rich beds have been located from over 30 km along the Tours-Poitiers High Speed Line (LGV) during earthworks prior to its construction, and in particular amber was collected from Scorbé-Clairvaux (locality of La Bergeonneau) to the north of Poitiers. The paper describes also amber pieces from Châtellerault (locality of La Désirée) discovered during the development of sewage treatment plant along the Vienne river. Lower Cenomanian shelly sandstones and siltstones of Scorbé-Clairvaux contain rare amber pieces associated with seed plants ( Frenelopsis sp., Nehvizdya sp., and angiosperm seeds) and a diversified fauna, composed of micro-remains of 27 taxa, comprising elasmobranchs ( Haimirichia amonensis Cappetta and Case, 1975, Protolama sp. and Squalicorax sp.), actinopterygians ( Enchodus sp. and Pycnodontidae), reptiles including vertebrae the marine snake Simoliophis rochebrunei Sauvage, 1880, some rare helochelydrid plates ( cf. Plastremys ), teeth of three crocodilian families (Atoposauridae, Goniopholididae and Bernissartiidae) and an undetermined dinosaurian long bone fragment.; Un grand nombre de niveaux riches en fossiles a été trouvé sur plus de 30 km le long de la Ligne à Grande Vitesse (LGV) Tours-Poitiers pendant les terrassements préalables à sa construction, et en particulier de l’ambre sur le site de la Bergeonneau à Scorbé-Clairvaux au nord de Poitiers. De l’ambre a également été collecté sur les bords de la Vienne au lieu-dit de La Désirée à Châtellerault lors de travaux d’aménagement d’une station d’épuration. Les grès coquillers et les roches argileuses du Cénomanien inférieur de Scorbé-Clairvaux contiennent de rares morceaux d’ambre associés à des méso-fossiles de plantes à graines ( Frenelopsis sp., Nehvizdya sp. et des graines) et 27 taxons micro-fossiles de vertébrés, dont des élasmobranches (en particulier Haimirichia amonensis Cappetta et Case, 1975, Protolama sp. et Squalicorax sp), des actinoptérygiens ( Enchodus sp. et Pycnodontidae), des reptiles incluant des vertèbres du serpent marin Simoliophis rochebrunei Sauvage, 1880, quelques rares plaques d’une tortue helochelydridée ( cf. Plastremys) , des dents de trois familles de crocodiliens (Atoposauridae, Goniopholididae et Bernissartiidae) ainsi qu’un fragment d’os long de dinosaurien indéterminé.

We report a new, small-sized atoposaurid crocodyliform from the Upper Jurassic of Langenberg, Northeastern Germany. Atoposaurids are small-sized Mesozoic crocodyliforms of mainly European distribution, which are considered to be phylogenetically close to the origin of Eusuchia. Knoetschkesuchus langenbergensis gen. nov. sp. nov. is represented by two well-preserved skulls and additional cranial and postcranial remains representing different ontogenetic stages. 3D reconstructions of a juvenile skull based on micro-computed tomography allow the most detailed description of cranial remains of any atoposaurid hitherto presented. Our new analysis contradicts previous preliminary assignment of the Langenberg atoposaurids to Theriosuchus. Knoetschkesuchus gen. nov. is characterized in particular by the presence of two dental morphotypes in the maxilla and dentary, slit-like secondary choanae within a narrow groove on the surface of the pterygoid, absence of lacrimonasal contact, presence of an antorbital foramen and an external mandibular fenestra, and proportional characters of the interorbital and intertemporal region. A similar combination of characters allows attribution of Theriosuchus guimarotae to Knoetschkesuchus, forming the new combination Knoetschkesuchus guimarotae. Our analysis provides an osteological basis for the separation of Theriosuchus and Knoetschkesuchus and helps further delineate generic differences in other closely related crocodylomorphs. Our phylogenetic analysis corroborates inclusion of Knoetschkesuchus into Atoposauridae and supports a position of Atoposauridae within Eusuchia.

Atoposaurids were a clade of semiaquatic crocodyliforms known from the Late Jurassic to the latest Cretaceous. Tentative remains from Europe, Morocco, and Madagascar may extend their range into the Middle Jurassic. Here we report the first unambiguous Middle Jurassic (late Bajocian–Bathonian) atoposaurid: an anterior dentary from the Isle of Skye, Scotland, UK. A comprehensive review of atoposaurid specimens demonstrates that this dentary can be referred to Theriosuchus based on several derived characters, and differs from the five previously recognized species within this genus. Despite several diagnostic features, we conservatively refer it to Theriosuchus sp., pending the discovery of more complete material. As the oldest known definitively diagnostic atoposaurid, this discovery indicates that the oldest members of this group were small-bodied, had heterodont dentition, and were most likely widespread components of European faunas. Our review of mandibular and dental features in atoposaurids not only allows us to present a revised diagnosis of Theriosuchus, but also reveals a great amount of variability within this genus, and indicates that there are currently five valid species that can be differentiated by unique combinations of dental characteristics. This variability can be included in future broad-scale cladistics analyses of atoposaurids and closely related crocodyliforms, which promise to help untangle the complicated taxonomy and evolutionary history of Atoposauridae. © 2015 The Authors. Zoological Journal of the Linnean Society published by John Wiley & Sons Ltd on behalf of The Linnean Society of London

Crocodiles have long been regarded as living fossils, animals that entered an evolutionary stasis and barely changed since the Mesozoic Era. Furthermore, with the possible exception of the Indian gharial (Gavialis gangeticus), living crocodiles are usually characterized by their relatively uniform body plan and amphibious mode of life. This generalization was probably based in that the three major living lineages of crocodiles (crocodylids, alligatoroids, and gavialoids) appeared in the Cretaceous and have maintained relatively unchanged morphologies since then. The evolution of these modern lineages of crocodiles (the crown-based clade Crocodylia sensu Benton & Clark, 1988; see Fig. 1), however, has far more diversity and disparity than usually reported (Brochu, 2001) and much of the assumed homogeneity is based on a lack of detailed studies and a disregard of bizarre fossil taxa, such as the gigantic, duck-billed nettosuchids (Brochu, 1999) or the high-snouted terrestrial pristichampsines (Rossmann, 2000). In addition to crown-group Crocodylia, a large number of closely-related fossil taxa form a more inclusive clade, Crocodyliformes (sensu Benton & Clark, 1988; see Fig. 1). This group had previously been regarded as the Order Crocodilia (Kalin, 1955; Romer, 1956; Kuhn, 1968) and has an outstanding diversity in the anatomy and ecological niches of its members. The most ancient record of Crocodyliformes, Hemiprotosuchus leali (Bonaparte, 1972), from the Late Triassic of Argentina, represents the most basal clade of crocodyliforms (Protosuchidae). Protosuchids (and other basal crocodyliforms previously thought to form a paraphyletic Protosuchia; Fig. 1) were small-bodied animals (usually less than 1 metre long) that achieved a worldwide distribution by the Early Jurassic (and survived to the Cretaceous in Central Asia). The Early Jurassic seems to have been a critical period in the evolution of Crocodyliformes, given that ghost lineages of multiple clades extend back to this time, suggesting the existence of a major radiation of this group during this epoch. Much of the Jurassic record of crocodyliforms is, however, restricted to two groups: the above mentioned basal crocodyliforms and the marine thalattosuchians (teleosaurids and metriorhynchids). This group is particularly interesting given it represents the only group of Archosauria completely adapted to the marine environment, having paddle-like forelimbs, a hypocercal tail, and excretory salt glands (Fernandez & Gasparini, 2000; Fernandez & Herrera, 2009). In spite of the wealth of fossils in this clade, its phylogenetic affinities are highly debated and constitute the major unsolved problem in crocodyliform systematics (Clark, 1994; Larsson & Sues, 2007; Jouve, 2009; Pol & Gasparini, 2009). The Jurassic fossil record of other terrestrial groups of Crocodyliformes is scarce (Tykoski et al., 2002) until the Late Jurassic, when members of the large clade Neosuchia become abundant in fluvial and lacustrine deposits in the northern hemisphere. This record includes the dwarf species of Atoposauridae (Buscalioni & Sanz, 1988) and the often gigantic Goniopholididae (Fig. 1). The Cretaceous, in contrast, was undoubtly the time when crocodyliforms were most abundant and diverse. During this period, the crocodyliform fauna of the northern hemisphere was basically composed of relictual basal taxa that survived in Central Asia (Wu, Brinkman & Lu, 1994; Wu, Sues & Dong, 1997; *Corresponding author. E-mail: dpol@mef.org.ar Zoological Journal of the Linnean Society, 2011, 163, S1–S6. With 3 figures

A slab from the Late Jurassic (Early Tithonian) lithographic limestone exhibiting skeletal material of an atoposaurid crocodyliform associated with four echinoids from the vicinity of Kelheim (S-Germany) is described. The atoposaurid is represented by a row of dorsal paravertebral osteoderms, caudal osteoderms, a caudal vertebra and haemapophyses, dorsal ribs, and parts of the right fore- and hindlimb. Some of the bones have been prepared out of the slab and most of them are preserved three-dimensionally, which is in contrast to the general much flattened preservation of atoposaurid skeletons. This well preserved specimen allows one of the most detailed descriptions of an atoposaurid limb skeleton so far, yielding in particular well preserved manual elements. By comparison with all other known atoposaurid taxa, the specimen can be determined to belong to the genus Alligatorellus based on an identical morphology of osteoderms. In contrast, a high ontogenetic variety and missing data make comparisons of limb ratios in different atoposaurids virtually useless for taxonomy. Femoral and tibial lengths suggest that this specimen is the largest atoposaurid known from the Solnhofen-Eichstätt region. It is suggested that the crocodyliform carcass has been washed into the lagoon and was subsequently embedded together with the tests of four holectypoid echinoids, which probably populated the lagoon. doi:10.1002/mmng.201100007

Small terrestrial non-eusuchian mesoeucrocodylians are common components of Cretaceous assemblages of Gondwanan provinces with notosuchians and araripesuchids as flagship taxa in South America, Africa and Madagascar, well into the Late Cretaceous. On the other hand, these are exceedingly rare in Laurasian landmasses during the Late Cretaceous. Small terrestrial mesoeucrocodylians from Europe were often referred to the genus Theriosuchus, a taxon with stratigraphic range extending from the Late Jurassic to the late Early Cretaceous. Theriosuchus is abundantly reported from various European localities, although Asiatic and possibly North American members are also known. It has often been closely associated with the first modern crocodilians, members of the Eusuchia, because of the presence of procoelous vertebrae, a widespread key character diagnosing the Eusuchia. Nevertheless, the relationships of Theriosuchus have not been explored in detail although one species, Theriosuchus pusillus, has been extensively described and referred in numerous works. Here, we describe a new basal mesoeucrocodylian, Theriosuchus sympiestodon sp. nov. from the Maastrichtian of the Haţeg Basin, Romania, suggesting a large temporal gap (about 58 myr) in the fossil record of the genus. Inclusion of the new taxon, along with Theriosuchus guimarotae, in a phylogenetic analysis confirms its referral to the genus Theriosuchus, within a monophyletic atoposaurid clade. Although phylogenetic resolution within this clade is still poor, the new taxon appears, on morphological grounds, to be most closely related to T. pusillus. The relationships of Atoposauridae within Mesoeucrocodylia and especially to Neosuchia are discussed in light of the results of the present contribution as well as from recent work. Our results raise the possibility that Atoposauridae might not be regarded as a derived neosuchian clade anymore, although further investigation of the neosuchian interrelationships is needed. Reports of isolated teeth referable to a closely related taxon from the Upper Cretaceous of Romania and France, together with the presence of Doratodon and Ischyrochampsa, indicate a previously unsuspected diverse assemblage of non-eusuchian mesoeucrocodylians in the Late Cretaceous European archipelago.

We describe a partial crocodilian skull from the Mesozoic non-marine sediments of the Khorat Plateau Sao Khua Formation (Berriasian-Barremian) in northeastern Thailand and assign it to Theriosuchus grandinaris sp. nov. An isolated dentary from the Phu Kradung Formation (latest Jurassic–Early Cretaceous) is also tentatively assigned to the genus Theriosuchus, and an isolated tooth from the Khok Kruat Formation (Aptian-Albian) may belong to this genus. The Thai fossils represent the first unambiguous evidence of presence of Theriosuchus outside Europe. Its occurrence in Thailand increases the known diversity of neosuchian crocodyliforms from Southeast Asia and suggests that Atoposauridae had a wide geographical distribution from the Late Jurassic to the Early Cretaceous.

Atoposaurids are a group of small-bodied, extinct crocodyliforms, regarded as an important component of Jurassic and Cretaceous Laurasian semi-aquatic ecosystems. Despite the group being known for over 150 years, the taxonomic composition of Atoposauridae and its position within Crocodyliformes are unresolved. Uncertainty revolves around their placement within Neosuchia, in which they have been found to occupy a range of positions from the most basal neosuchian clade to more crownward eusuchians. This problem stems from a lack of adequate taxonomic treatment of specimens assigned to Atoposauridae, and key taxa such as Theriosuchus have become taxonomic ‘waste baskets’. Here, we incorporate all putative atoposaurid species into a new phylogenetic data matrix comprising 24 taxa scored for 329 characters. Many of our characters are heavily revised or novel to this study, and several ingroup taxa have never previously been included in a phylogenetic analysis. Parsimony and Bayesian approaches both recover Atoposauridae as a basal clade within Neosuchia, more stemward than coelognathosuchians, bernissartiids, and paralligatorids. Atoposauridae is a much more exclusive clade than previously recognized, comprising just three genera (Alligatorellus, Alligatorium, and Atoposaurus) that were restricted to the Late Jurassic of western Europe, and went extinct at the Jurassic/Cretaceous boundary. A putative Gondwanan atoposaurid (Brillanceausuchus) is recovered as a paralligatorid. Our results exclude both Montsecosuchus and Theriosuchus from Atoposauridae. Theriosuchus is polyphyletic, forming two groupings of advanced neosuchians. Theriosuchus (restricted to Theriosuchus pusillus, Theriosuchus guimarotae, and Theriosuchus grandinaris) spanned the Middle Jurassic to early Late Cretaceous, and is known from Eurasia and North Africa. Two Cretaceous species previously assigned to Theriosuchus (‘Theriosuchus’ ibericus and ‘Theriosuchus’ sympiestodon) are shown to be nested within Paralligatoridae, and we assign them to the new genus Sabresuchus. The revised phylogenetic placement of Theriosuchus has several implications for our understanding of eusuchian evolution. Firstly, the presence of fully pterygoidean choanae, previously regarded as a defining characteristic of Eusuchia, is not found in some basal members of Eusuchia. However, eusuchians can be distinguished from Theriosuchus and other basal neosuchians in that their choanae are posteriorly positioned, with an anterior margin medial to the posterior edge of the suborbital fenestra. This feature distinguishes eusuchians from Theriosuchus and more basal neosuchians. Secondly, our refined understanding of Theriosuchus implies that this taxon possessed only amphicoelous presacral vertebrae, and therefore fully developed vertebral procoely is likely to have evolved only once in Crocodylomorpha, on the lineage leading to Eusuchia. These and other findings presented herein will provide an important framework for understanding the neosuchian–eusuchian transition.

A new mesoeucrocodylian, Pachycheilosuchus trinquei, from the Lower Cretaceous (Albian) Glen Rose Formation, exhibits progressive caudal-to-cranial vertebral procoely. This modification is characterized by an intermediate semi-procoelous condition in which the posterior condyle is dimpled by a concavity. Pachycheilosuchus differs from all known crocodyliforms in having an expanded maxillary margin that displaces the tooth row medially, and in possessing a cervical shield formed by the complete fusion of six osteoderms. Phylogenetic analysis indicates a sister taxon relationship with the weakly defined Atoposauridae. The presence of variable procoely in both Pachycheilosuchus and the closely related atoposaurid Theriosuchus indicates convergent evolution of the character with Eusuchia. Sediments at the locality were deposited in near-shore, marine-to-brackish waters, suggesting that Pachycheilosuchus inhabited euryhaline marine environments.

Atoposaurids were a clade of semiaquatic crocodyliforms known from the Late Jurassic to the latest Cretaceous. Tentative remains from Europe, Morocco, and Madagascar may extend their range into the Middle Jurassic. Here we report the first unambiguous Middle Jurassic (late Bajocian–Bathonian) atoposaurid: an anterior dentary from the Isle of Skye, Scotland, UK. A comprehensive review of atoposaurid specimens demonstrates that this dentary can be referred to T heriosuchus based on several derived characters, and differs from the five previously recognized species within this genus. Despite several diagnostic features, we conservatively refer it to T heriosuchus sp., pending the discovery of more complete material. As the oldest known definitively diagnostic atoposaurid, this discovery indicates that the oldest members of this group were small‐bodied, had heterodont dentition, and were most likely widespread components of European faunas. Our review of mandibular and dental features in atoposaurids not only allows us to present a revised diagnosis of T heriosuchus, but also reveals a great amount of variability within this genus, and indicates that there are currently five valid species that can be differentiated by unique combinations of dental characteristics. This variability can be included in future broad‐scale cladistics analyses of atoposaurids and closely related crocodyliforms, which promise to help untangle the complicated taxonomy and evolutionary history of Atoposauridae. © 2015 The Authors. Zoological Journal of the Linnean Society published by John Wiley & Sons Ltd on behalf of The Linnean Society of London

Atoposaurid crocodyliforms represent an important faunal component of Late Jurassic to Early Cretaceous Laurasian semi-aquatic to terrestrial ecosystems, with numerous spatiotemporally contemporaneous atoposaurids known from western Europe. In particular, the Late Jurassic of France and Germany records evidence for high diversity and possible sympatric atoposaurid species belonging to Alligatorellus, Alligatorium and Atoposaurus. However, atoposaurid taxonomy has received little attention, and many species are in need of revision. As such, this potentially high European diversity within a narrow spatiotemporal range might be a taxonomic artefact. Here we provide a taxonomic and anatomical revision of the Late Jurassic atoposaurid Alligatorellus. Initially described as A. beaumonti from the Kimmeridgian of Cerin, eastern France, additional material from the Tithonian of Solnhofen, south-eastern Germany, was subsequently referred to this species, with the two occurrences differentiated as A. beaumonti beaumonti and A. beaumonti bavaricus, respectively. We provide a revised diagnosis for the genus Alligatorellus, and note a number of anatomical differences between the French and German specimens, including osteoderm morphology and the configuration and pattern of sculpting of cranial elements. Consequently, we restrict the name Alligatorellus beaumonti to include only the French remains, and raise the rank of the German material to a distinct species: Alligatorellus bavaricus. A new diagnosis is provided for both species, and we suggest that a recently referred specimen from a coeval German locality cannot be conclusively referred to Alligatorellus. Although it has previously been suggested that Alligatorellus, Alligatorium and Atoposaurus might represent a single growth series of one species, we find no conclusive evidence to support this proposal, and provide a number of morphological differences to distinguish these three taxa that appear to be independent of ontogeny. Consequently, we interpret high atoposaurid diversity in the Late Jurassic island archipelago of western Europe as a genuine biological signal, with closely related species of Alligatorellus, Alligatorium and Atoposaurus in both French and German basins providing evidence for allopatric speciation, potentially driven by fluctuating highstand sea levels.

We present a detailed morphological description of the type-locality cranial material of Theriosuchus sympiestodon Martin, Rabi, and Csiki, 2010 from the Maastrichtian Densuş-Ciula Formation of the Haţeg Basin, Romania together with new material of isolated cranial elements and teeth from various sites of the same general area. The recognition of several individuals of distinct sizes allows for an assessment of ontogenetic variation in this taxon. New material, consisting of isolated teeth and an incomplete maxilla with in situ teeth, coming from various late Campanian/early Maastrichtian sites in southern France is referable to ?Theriosuchus sp. and hints to a rare but widespread distribution of Theriosuchus in the Late Cretaceous European archipelago.

A new fossiliferous locality from the Middle Jurassic (Bathonian) of the Grands Causses (Gard, France) is described. The layer is rich in gyrogonites of Porochara douzensis . The only ostracod carapace found is identified as Darwinula magna . As for vertebrates, teeth of Hybodontiformes, teeth and scales of Semionotiformes, and one fragmentary tooth of Crocodyliformes have been collected and are determined as Hybodus sp., Lepidotes sp., and Atoposauridae indet., respectively. The assemblage is representative of a Jurassic coastal environment with freshwater ponds and lagoons.

Cranial and postcranial remains from the Laolonghuoze locality in the Ordos Basin, Inner Mongolia (China), represent a previously unrecorded taxon of crocodyliform archosaurs from the Lower Cretaceous Luohandong Formation (Zhidan Group). Several cranial features indicate that this form is referable to the Atoposauridae, which were previously definitely known only from the Upper Jurassic and Lower Cretaceous of Europe. Certain derived characters further indicate that the Ordos material is closely related to, if not actually referable to, Theriosuchus. The Ordos atoposaurid differs from the species of Theriosuchus in only a few features. In view of its fragmentary nature, the new material is identified as cf. Theriosuchus sp. at present.

Alligatorium depereti, a species of the family Atoposauridae from the Upper Berriasian-Lower Valanginian (Early Cretaceous) of Spain, has neither been revised nor redescribed since the first decade...

The cranial morphology of Mariliasuchus amarali, a poorly known notosuchian from the Late Cretaceous of Southeastern Brazil, is redescribed based on new material. Its phylogenetic affinities within Crocodylomorpha are evaluated through a parsimony analysis involving 46 taxa and 198 characters. Mariliasuchus is nested well inside the clade Notosuchia, as the sister group of Comahuesuchus, a derived notosuchian from the Late Cretaceous of Argentina. Both taxa share the following unambiguous synapomorphies: ventral half of the lacrimal tapering posteroventrally, not contacting or only slightly contacting the jugal; presence of a large foramen on the lateral surface of the anterior part of the jugal; presence of procumbent premaxillary and anterior dentary alveoli; and ectopterygoids that do not participate of the palatine bar. The presence of procumbent premaxillary teeth, specialized tooth crown morphology, and fore–aft jaw movements suggests that this group presented complex jaw movements related ...

A systematic revision of the family Atoposauridae is presented, interpreting and reviewing their relationships. The seventy‐one characters have been divided into cranial, postcranial and metric which have been used in three separate cladistic analyses in order to discuss their concordance. Polarities, in each case, have been deduced from distinct outgroups. We have used a PHYLIP program (version 2.9). There are five valid taxa of Atoposauridae: Alligatorellus beaumonti (rejecting the two subspecific taxa) Alligatorium meyeri, Theriosuchus pusillus. Alligatorium depereti (which is transferred to a new genus Montsecosuchus) and Aloposaurus (discussed as a nomen dubium). The three cladograms are not fully concordant. The relative level of derivation in postcranial and cranial characters suggests congruence. The metric traits seem to retain, in general, a primitive condition. The final proposed cladogram clusters Alligatorium + Alligatorellus as the sister group of Montsecosuchus + Theriosuchus.

Atoposaurids are a group of small-bodied, extinct crocodyliforms, regarded as an important component of Jurassic and Cretaceous Laurasian semi-aquatic ecosystems. Despite the group being known for over 150 years, the taxonomic composition of Atoposauridae and its position within Crocodyliformes are unresolved. Uncertainty revolves around their placement within Neosuchia, in which they have been found to occupy a range of positions from the most basal neosuchian clade to more crownward eusuchians. This problem stems from a lack of adequate taxonomic treatment of specimens assigned to Atoposauridae, and key taxa such as Theriosuchus have become taxonomic ‘waste baskets’. Here, we incorporate all putative atoposaurid species into a new phylogenetic data matrix comprising 24 taxa scored for 329 characters. Many of our characters are heavily revised or novel to this study, and several ingroup taxa have never previously been included in a phylogenetic analysis. Parsimony and Bayesian approaches both recover Atoposauridae as a basal clade within Neosuchia, more stemward than coelognathosuchians, bernissartiids, and paralligatorids. Atoposauridae is a much more exclusive clade than previously recognized, comprising just three genera (Alligatorellus, Alligatorium, and Atoposaurus) that were restricted to the Late Jurassic of western Europe, and went extinct at the Jurassic/Cretaceous boundary. A putative Gondwanan atoposaurid (Brillanceausuchus) is recovered as a paralligatorid. Our results exclude both Montsecosuchus and Theriosuchus from Atoposauridae. Theriosuchus is polyphyletic, forming two groupings of advanced neosuchians. Theriosuchus (restricted to Theriosuchus pusillus, Theriosuchus guimarotae, and Theriosuchus grandinaris) spanned the Middle Jurassic to early Late Cretaceous, and is known from Eurasia and North Africa. Two Cretaceous species previously assigned to Theriosuchus (‘Theriosuchus’ ibericus and ‘Theriosuchus’ sympiestodon) are shown to be nested within Paralligatoridae, and we assign them to the new genus Sabresuchus. The revised phylogenetic placement of Theriosuchus has several implications for our understanding of eusuchian evolution. Firstly, the presence of fully pterygoidean choanae, previously regarded as a defining characteristic of Eusuchia, is not found in some basal members of Eusuchia. However, eusuchians can be distinguished from Theriosuchus and other basal neosuchians in that their choanae are posteriorly positioned, with an anterior margin medial to the posterior edge of the suborbital fenestra. This feature distinguishes eusuchians from Theriosuchus and more basal neosuchians. Secondly, our refined understanding of Theriosuchus implies that this taxon possessed only amphicoelous presacral vertebrae, and therefore fully developed vertebral procoely is likely to have evolved only once in Crocodylomorpha, on the lineage leading to Eusuchia. These and other findings presented herein will provide an important framework for understanding the neosuchian–eusuchian transition.