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Much of a skeleton of Dibothrosuchus elaphros from the Lower Lufeng Group (Lower Jurassic) of Yunnan, China permits a detailed review of the anatomy and relationships of sphenosuchian crocodylomorphs. The skull is strongly built, akinetic, and monimostylic. The quadrate shows three dorsal processes that are firmly sutured to the skull roof and the braincase. The otic capsule is essentially crocodilian, and the tympanic pneumaticities are more elaborate than in extant forms. The animal possessed refined hearing ability and was probably vocal. The coracoid has an extremely elongated, posteriorly directed postglenoid process. The humerus bears an oval depression anteriorly near the head, and the radiale and ulnare are longer than the metacarpals. The limbs are long and slender, adapted for quadrupedal terrestrial gait. The estimated total length was 1.3 m. Phylogenetic analysis of 65 characters indicates the monophyly of the Sphenosuchia. Within the Sphenosuchia, Saltoposuchus (=Terrestrisuchus), Ps...

A new genus and species of giant crocodylomorph from the Upper Triassic of New Mexico is described.Redondavenator quayensis n. gen. et n. sp. (Crocodylomorpha: Sphenosuchia) has a very long posterior process of the premaxilla that fits between the nasal and the maxilla, and a long postglenoid process on the coracoid. These synapomorphies place it within the Crocodylomorpha.Redondavenator also has a System of grooves and pits that cover the anterior portions of the maxillae, the entire premaxillae, and the anterior part of the nasal. Possible foramina among the network of grooves and pits on the anterior portion of the skull may represent a rudimentary sensory System that is common to many extinct and ail extant crocodilians. Its exact phylogenetic position could not be determined from the preserved material, but key characters suggest a phylogenetic position near the base of Sphenosuchia.

The skull of living crocodylians is highly solidified and the jaw closing muscles are enlarged1, 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-side2; however, fossils indicate that they evolved from terrestrial forms. The most cursorial of these fossils3,4,5,6 are small, gracile forms often grouped together as the Sphenosuchia, with fully erect, slender limbs; their relationships, however, are poorly understood5,7,8,9,10. 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.

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.