Fossil range: Early Jurassic
| Scientific classification
Eopneumatosuchus is an extinct basal crocodyliform for which Fossils have been found at two localities within the Kayenta Formation of Arizona. Both localities are around 20 miles southeast of the Grand Canyon and in close proximity to one another. The localities probably date back to the Early Jurassic, most likely to the Sinemurian stage.
Eopneumatosuchus was initially considered to be a protosuchian, first proposed when the genus was named in 1980. However, this classification was later questioned on the basis of several features of the holotype material, and as a result it is no longer considered to be within Protosuchia. Particular features of the posterior part of the cranium, the only material associated with the genus, suggest that Eopneumatosuchus may have close relations with Early Jurassic teleosaurs. The large supratemporal fenestrae of Eopneumatosuchus are characteristic of longirostrine crocodilians. Despite the similar cranial morphology with crocodilians, the genus is currently regarded as a basal crocodyliform. Nonetheless, it is considered to be more derived than protosuchians such as Protosuchus, found from the Moenave Formation, whose deposition preceded that of the Kayenta Formation. The basal cranium has many cavities that make up a complex typanic pneumatic system for which the genus is named. These types of cavities can also be seen in some protosuchians such as Protosuchus and Hemiprotosuchus, although they are less elongated than in Eopneumatosuchus.
- ^ Crompton, A. W. and Smith, K. K. (1980). A new genus and species from the Kayenta Formation (Late Triassic?) of Northern Arizona. In Jacobs, L (ed.), Aspects of Vertebrate History Flagstaff: Museum of Northern Arizona Press, pp. 193-217.
- ^ Hecht, M. K. and Tarsitano, S. F. (1983). On the cranial morphology of the Protosuchia, Notosuchia and Eusuchia. Neues Jahrbuch für Geologie und Paläontologie Monatshefte 1983(11):657-668.
- ^ Clark, J. M. and Fastovsky, D. E. (1989) Vertebrate biostratigraphy of the Glen Canyon Group in northern Arizona. In Padian, K. (ed.) The Beginning of the Age of Dinosaurs: Faunal Change Across the Triassic-Jurassic Boundary Cambridge: Cambridge University Press.
- ^ Dufeau, D. L. and Witmer, L. M. (2007). Ontogeny and phylogeny of the tympanic pneumatic system of crocodyliform archosaurs. Journal of Morphology 268(12)