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Non‐crocodyliform crocodylomorphs, formerly referred to the informal group 'Sphenosuchia', are the earliest known crocodylomorph precursors of extant crocodylians. They are therefore crucial for our understanding of early crocodylian evolution and the origin of typical crocodylian characteristics, such as the formation of a secondary palate, complex cranial pneumaticity, and a reinforced braincase. Terrestrisuchus gracilis, known from the Upper Triassic fissure fill deposits of Pant‐y‐Ffynnon in southern Wales, is represented by almost 200 specimens, comprising articulated, partially associated, and isolated remains. In this contribution we provide a taxonomic revision of Terrestrisuchus gracilis and redescribe its cranial anatomy in detail, based in part on novel micro‐computed tomography data. The posterior skull region is extensively pneumatized as indicated, among other features, by large pre‐ and postcarotid recesses on the parabasisphenoid, and a large pneumatic cavity in the articular of the mandible. In contrast, the quadrate forms only a small, unfused contact with the prootic, suggesting that complex pneumatization of the postorbital region pre‐dated the co‐ossification of the quadrate and braincase in Crocodylomorpha. Terrestrisuchus gracilis preserves an ossified basihyal, which represents the first occurrence of this bone in non‐avemetatarsalian archosaurs. Finally, we show that Terrestrisuchus gracilis was probably cathemeral (i.e. active in a range of light levels), based on a phylogenetic flexible discriminant analysis of the relative dimensions of the sclerotic ring and orbit. [ABSTRACT FROM AUTHOR]

The holotype of Junggarsuchus sloani, from the Shishugou Formation (early Late Jurassic) of Xinjiang, China, consists of a nearly complete skull and the anterior half of an articulated skeleton, including the pectoral girdles, nearly complete forelimbs, vertebral column, and ribs. Here, we describe its anatomy and compare it to other early diverging crocodylomorphs, based in part on CT scans of its skull and that of Dibothrosuchus elaphros from the Early Jurassic of China. Junggarsuchus shares many features with a cursorial assemblage of crocodylomorphs, informally known as "sphenosuchians," whose relationships are poorly understood. However, it also displays several derived crocodyliform features that are not found among most "sphenosuchians." Our phylogenetic analysis corroborates the hypothesis that Junggarsuchus is closer to Crocodyliformes, including living crocodylians, than are Dibothrosuchus and Sphenosuchus, but not as close to crocodyliforms as Almadasuchus and Macelognathus, and that the "Sphenosuchia" are a paraphyletic assemblage. D. elaphros and Sphenosuchus acutus are hypothesized to be more closely related to Crocodyliformes than are the remaining non-crocodyliform crocodylomorphs, which form several smaller groups but are largely unresolved., (© 2022 The Authors. The Anatomical Record published by Wiley Periodicals LLC on behalf of American Association for Anatomy.)

The skull of living crocodylians is highly solidified and the jaw closing muscles are enlarged, allowing for prey capture by prolonged crushing between the jaws. Living species are all semi-aquatic, with sprawling limbs and a broad body that moves mainly from side-to-side; however, fossils indicate that they evolved from terrestrial forms. The most cursorial of these fossils are small, gracile forms often grouped together as the Sphenosuchia, with fully erect, slender limbs; their relationships, however, are poorly understood. A new crocodylomorph from deposits in northwestern China of the poorly known Middle Jurassic epoch possesses a skull with several adaptations typical of living crocodylians. Postcranially it is similar to sphenosuchians but with even greater adaptations for cursoriality in the forelimb. Here we show, through phylogenetic analysis, that it is the closest relative of the large group Crocodyliformes, including living crocodylians. Thus, important features of the modern crocodylian skull evolved during a phase when the postcranial skeleton was evolving towards greater cursoriality, rather than towards their current semi-aquatic habitus. [ABSTRACT FROM AUTHOR]

Hsisosuchus, with three known species, was the most common genus of crocodyliforms in the Sichuan Basin during the Jurassic. However, the overall shape of the ventral trunk shield of osteoderms has not been clarified due to the lack of complete specimens. A new specimen of Hsisosuchus recently recovered from the Upper Jurassic of Yunnan has the nearly complete ventral trunk shield preserved. This specimen provides an example for the first time for us to understand the shape and the way of the arrangement of the osteoderms in the ventral trunk shield in the genus. Compared with the articulated part of the ventral trunk shield preserved in two of the three species of the genus, the osteoderms of the ventral trunk shield of the new specimen are different in both shape and way of arrangement, indicating that the pattern of the ventral trunk shield is not constant within Hsisosuchus. With no skull and much of the postcranial skeleton poorly preserved as well as no corresponding element that can be used to compare with all the three species, the new specimen was considered as an indeterminate species of Hsisosuchus, awaiting more materials to clarify the problem. [ABSTRACT FROM AUTHOR]

Present‐day crocodylians exhibit a remarkably akinetic skull with a highly modified braincase. We present a comprehensive description of the neurocranial osteology of extant crocodylians, with notes on the development of individual skeletal elements and a discussion of the terminology used for this project. The quadrate is rigidly fixed by multiple contacts with most braincase elements. The parabasisphenoid is sutured to the pterygoids (palate) and the quadrate (suspensorium); as a result, the basipterygoid joint is completely immobilized. The prootic is reduced and externally concealed by the quadrate. It has a verticalized buttress that participates in the canal for the temporal vasculature. The ventrolateral processes of the otoccipitals completely cover the posteroventral region of the braincase, enclose the occipital nerves and blood vessels in narrow bony canals and also provide additional sutural contacts between the braincase elements and further consolidate the posterior portion of the crocodylian skull. The otic capsule of crocodylians has a characteristic cochlear prominence that corresponds to the lateral route of the perilymphatic sac. Complex internal structures of the otoccipital (extracapsular buttress) additionally arrange the neurovascular structures of the periotic space of the cranium. Most of the braincase elements of crocodylians are excavated by the paratympanic pneumatic sinuses. The braincase in various extant crocodylians has an overall similar structure with some consistent variation between taxa. Several newly observed features of the braincase are present in Gavialis gangeticus and extant members of Crocodylidae to the exclusion of alligatorids: the reduced exposure of the prootic buttress on the floor of the temporal canal, the sagittal nuchal crest of the supraoccipital projecting posteriorly beyond the postoccipital processes and the reduced paratympanic pneumaticity. The most distinctive features of the crocodylian braincase (fixed quadrate and basipterygoid joint, consolidated occiput) evolved relatively rapidly at the base of Crocodylomorpha and accompanied the initial diversification of this clade during the Late Triassic and Early Jurassic. We hypothesize that profound rearrangements in the individual development of the braincases of basal crocodylomorphs underlie these rapid evolutionary modifications. These rearrangements are likely reflected in the embryonic development of extant crocodylians and include the involvement of neomorphic dermal anlagen in different portions of the developing chondrocranium, the extensive ossification of the palatoquadrate cartilage as a single expanded quadrate and the anteromedial inclination of the quadrate. [ABSTRACT FROM AUTHOR]

Almadasuchus figarii is a basal crocodylomorph recovered from the Upper Jurassic levels of the Cañadón Calcáreo Formation (Oxfordian–Tithonian) of Chubut, Argentina. This taxon is represented by cranial remains, which consist of partial snout and palatal remains; an excellently preserved posterior region of the skull; and isolated postcranial remains. The skull of the only specimen of the monotypic Almadasuchus was restudied using high‐resolution computed micro tomography. Almadasuchus has an apomorphic condition in its skull shared with the closest relatives of crocodyliforms (i.e. hallopodids) where the quadrates are sutured to the laterosphenoids and the otoccipital contacts the quadrate posterolaterally, reorganizing the exit of several cranial nerves (e.g. vagus foramen) and the entry of blood vessels (e.g. internal carotids) on the occipital surface of the skull. The endocast is tubular, as previously reported in thalattosuchians, but has a marked posterior step, and a strongly projected floccular recess as in other basal crocodylomorphs. Internally, the skull of Almadasuchus is heavily pneumatized, where different air cavities invade the bones of the suspensorium and braincase, both on its dorsal or ventral parts. Almadasuchus has a large basioccipital recess, which is formed by cavities that excavate the basioccipital and the posterior surface of the basisphenoid, and unlike other crocodylomorphs is connected with the basisphenoid pneumatizations. Ventral to the otic capsule, a pneumatic cavity surrounded by the otoccipital and basisphenoid is identified as the rhomboidal recess. The quadrate of Almadasuchus is highly pneumatized, being completely hollow, and the dorsal pneumatizations of the braincase are formed by the mastoid and facial antra, and a laterosphenoid cavity (trigeminal diverticulum). To better understand the origins of pneumatic features in living crocodylomorphs we studied cranial pneumaticity in the basal members of Crocodylomorpha and found that: (a) prootic pneumaticity may be a synapomorphy for the whole clade; (b) basisphenoid pneumaticity (pre‐, postcarotid and rostral recesses) is a derived feature among basal crocodylomorphs; (c) quadrate pneumatization is acquired later in the history of the group; and (d) the rhomboidal sinus is a shared derived trait of hallopodids and crocodyliforms. The marine thallatosuchians exhibit a reduction of the pneumaticity of the braincase and this reduction is evaluated considering the two phylogenetic positions proposed for the clade. [ABSTRACT FROM AUTHOR]

Although frequent in vertebrates (e.g. crocodylians, stem-tetrapods, turtles), the adaptive significance of bone ornamentation, that is the honeycomb-like pattern of pits and ridges that occur on the surface of dermal bones, remains poorly understood. In order to help assess the evolutionary history and ecological correlates of this character, ornamentation was quantified in 69 extant and extinct Pseudosuchia (taxa more closely related to crocodiles than to birds). This variable was related to the dominant habitat (terrestrial, amphibious, pelagic) of these taxa within a phylogenetic framework covering more than 250 Myr of evolution. The phylogenetic analyses reveal a significant correlation between the degree of bone ornamentation on the skull roof with lifestyle (terrestrial, amphibious, pelagic). A straightforward adaptive interpretation of these results is to be avoided because skull morphology has recently been shown to strongly influence local development of bone ornamentation in Crocodylia. Indeed, ornamentation in long-snouted amphibious forms scores low or nil values on the skull roof while scoring very high values on osteoderms. Our results also show that amphibious forms, whether marine or fluvial, have a high degree of ornamentation, whereas terrestrial and pelagic forms are either not ornamented or have a low level of ornamentation. It is hypothesized that the high development of ornamentation among semi-aquatic pseudosuchians has been positively selected because it improves basking efficiency in semi-aquatic ambush (i.e. poorly active) predators. This process would have occurred at the Triassic-Jurassic boundary. [ABSTRACT FROM AUTHOR]

Restudy of skulls and available postcrania of the proterochampsian archosauriform Proterochampsa barrionuevoi from the Ischigualasto Formation (Upper Triassic, Carnian) in the San Juan Province, Argentina, confirms that the genus is diagnosed by autapomorphies that include dermal sculpturing consisting of prominent ridges and nodular protuberances, a large hook-like lateral projection on the quadratojugal, an antorbital fossa restricted to a depression along the maxilla, lateral expansion of the premaxilla anterior to the premaxilla-maxilla contact, absence of a supratemporal fossa, exclusion of jugal from suborbital fenestra, basal tubera of parabasisphenoid facing ventrally and reaching laterally beyond the basipterygoid process, and a ventral lamina on the angular. Proterochampsa nodosa is a valid species distinguished from P. barrionuevoi by fewer cranial ridges with larger protuberances, relatively smaller supratemporal fenestrae and width of frontals between orbits less than that of the nasals. A phylogenetic analysis supports the monophyly of Proterochampsia consisting of Proterochampsa, Chanaresuchus bonapartei, Gualosuchus reigi, Tropidosuchus romeri and Cerritosaurus binsfeldi. A temporal separation between the two basal proterochampsians with earliest records in the Late Triassic ( Proterochampsa and Cerritosaurus) and Chanaresuchus, Gualosuchus and Tropidosuchus in the Middle Triassic indicates hidden proterochampsian diversity in the Middle Triassic. [ABSTRACT FROM AUTHOR]

An incomplete skull (SMNS 12352) from the Norian (Late Triassic), found at the same locality (Pfaffenhofen, Germany) as Procompsognathus triassicus, has previously been attributed to either a theropod or a crocodylomorph. The specimen is partially embedded in matrix and, therefore, was CT scanned so that the concealed portion could be visualized and a 3D model could be printed by means of rapid prototyping. Mainly based on the separation between the nasal and the antorbital fossa, the skull likely pertains to an indeterminate basal crocodylomorph (non-Crocodyliformes), which is, however, distinct from Saltoposuchus connectens. [ABSTRACT FROM AUTHOR]

Recent revision of the marine metriorhynchid crocodilians indicates that a partial skull previously assigned to the species Metriorhynchus superciliosus and newly discovered postcranial elements from the Kimmeridge Clay of Westbury, Wiltshire belong to a new species of metriorhynchid. This material is herein described and referred to a new species of the genus Dakosaurus, characterised by four apomorphies: the size and shape of the enlarged supratemporal fossae; relatively large teeth, and half the number in relatives; the robust and unornamented cranium; and the angle that the prefrontal makes with the long axis of the skull. In a new phylogenetic analysis, Dakosaurus carpenteri sp. nov. is the basal member of a clade containing also D. maximus and D. andiniensis: it is not so short-snouted and its teeth are not so few and large as in the other two species, but the new form illustrates the ecological transition among metriorhynchids from a piscivorous diet to high-order carnivory. [ABSTRACT FROM AUTHOR]

This paper presents a detailed description of the skull and part of the mandible of the crocodyliform reptile Hamadasuchus rebouli from the Kem Kem beds (Upper Cretaceous: Albian–Cenomanian) of south-eastern Morocco. This taxon of deep-snouted ziphodont crocodyliform can be diagnosed by a number of autapomorphies. Phylogenetic analysis of a diverse array of crocodylomorph taxa found strong support for a clade comprising H. rebouli, Peirosauridae, and Sebecus. The name Sebecia nom. nov. is proposed for this grouping, which is diagnosed by numerous characters, including the participation of the quadratojugal in the mandibular condyle. The distribution of this diverse and long-lived clade lends further support to the biogeographical hypothesis that faunal connections existed between Africa and South America well into mid-Cretaceous times. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 149, 533–567. [ABSTRACT FROM AUTHOR]