A ceratosaurid (Dinosauria, Theropoda) from the Late Jurassic-Early Cretaceous of Uruguay

Several teeth with ceratosaurid affinities from the Tacuarembo Formation (Kimmeridgian-Hautevirian) of Uruguay (South America) are reported herein. The most diagnostic specimen is a small rostrat crown (probably the first or second left premaxillary crown), the most conspicuous features of which are the presence of several, well-marked longitudinal grooves on the lingual face and the absence of mesial denticles. This combination of characters is only found in the Late Jurassic genus Ceratosaurus Marsh, 1884. The tooth was carefully compared with all potentially similar theropod teeth in order to discard non-ceratosaurid affinities. The occurrence of a South American ceratosaurid in the Tacuarembo Formation was not unexpected, given the temporal range known for the family and the probable Late Jurassic age independently proposed for the lower, fossiliferous member of this unit. Thus, the interpretation of this tooth as belonging to a Ceratosaurus-like ceratosaurid has important biostratigraphic implications, reinforcing the aforementioned hypothesis. Furthermore, it indicates the presence of the ceratosaurid lineage in South America earlier than recognized, the only ceratosaurid previously identified being the Argentinean Genyodectes, of probably Aptian-Albian age. The identification of this Ceratosaurus-like ceratosaurid allows the establishment of new links with several Late Jurassic faunas.