Thursday, February 2, 2012

[Paleontology • 2004] Uberabasuchus terrificus • a New Crocodylomorpha from the Bauru Basin (Upper Cretaceous), Brazil

A new fairly complete and articulated skull of a Peirosauridae crocodylomorph from Bauru Basin (Late Cretaceous), Brazil, is described. The fossil is from a level of clayish sandstone within Serra do Veadinho sequence, Peirópolis, Uberaba County, Minas Gerais State. The sedimentary strata of Serra do Veadinho belong to the Marília Formation (Serra da Galga Member), Bauru Group, considered to be Campanian-Maastrichtian in age. The species -Uberabasuchus terrificus sp. nov. - is a peirosaurid with moderately narrow snout, large round orbits protected by supraorbital bones of triangular shape and an antorbital fenestra bounded posteriorly by a deep groove. This fossil resembles Peirosaurus tormini Price, 1955 in the size pattern of premaxillary teeth and by showing a similar wedge-like maxillary process in the premaxilla. It also shares some morphological features with the other species of the Peirosauridae, namely the crocodylomorph Lomasuchus palpebrosus Gasparini, Chiappe and Fernandez, 1991 from Argentina. Their common features comprise a moderately narrow snout and the deep lateral groove at the premaxilla and maxilla articulation for the reception of a large mandibular tooth. However, the nasal participates in the external nares and does not divide the nasal aperture, producing a “beak-like” structure at the extremity of the snout which is unique among peirosaurids. The stratigraphic setting suggests that the specimen was buried when a flash flood overflowed the shallow channels of a braided fluvial system.

Parsimony analysis of 183 morphological characters is performed for 23 crocodylomorphs. Analysis of the morphological data matrix resulted in three most parsimonious trees (374 steps, CI = 0.679; RI = 0.826). The new species is closely related to Mahajangasuchus and both, in addition to Peirosaurus and Lomasuchus, compose the Peirosauridae.

Key words: Crocodylomorpha; Peirosauridae

2004. Uberabasuchus terrificus sp. nov., a New Crocodylomorpha from the Bauru Basin (Upper Cretaceous), Brazil. Gondwana Research, 7(4): 975-1002.