Revisiting the alleged record of Carcharodontosauridae (Theropoda: Allosauroidea) from the Upper Cretaceous Bauru Group, Brazil.

RAFAEL SOUZA; GIOVANNE CIDADE; JOAO MATOS; SILVIO PEREIRA; ANA CLARA COSTA; DOUGLAS RIFF; AGUSTIN MARTINELLI

San Juan

Congreso; IV Congreso Latinoamericano de Paleontología de Vertebrados; 2011

Carcharodontosauridae is a clade of large to giant mid-Cretaceous theropods whose derivate taxa have a Gondwanic distribution (Argentina and northern Africa), but basal members also occurred in Laurasian landmasses (Spain, China, USA), besides northern Africa. The most recent carcharodontosaurid comes from the Turonian of China, whereas the oldest record comes from the Barremian of Spain. Confident South American record ranged from Aptian to Turonian times. The monophyly of the Carcharodontosauridae is supported by a plethora of characters. Among these, the presence of teeth with compressed crowns bearing marginal and high enamel crenulations (wrinkles) has been treated traditionally by several authors as a keystone to diagnose this family, and to recognize new occurrences based on isolated teeth. However, recurrent studies have demonstrated how variable and widespread is this feature among theropods, such as Spinosauroidea, Tyrannosauroidea, and Abelisauridae (e.g., Brusatte et al. 2007). Unfortunately such unsupported practice is still common in the treatment of several records of isolated theropod teeth from the Upper Cretaceous Bauru Group of southeastern Brazil. Therefore, we reanalyzed a collection of 20 isolated teeth from the Campanian-Maastrichtian Adamantina Formation of São Paulo (UFRJ-DG 379-Rd - Alfredo Marcondes) and Minas Gerais State (MMR/UFU-PV 005 - Prata municipality) and from the Maastrichtian Serra da Galga Member of the Marília Formation in Minas Gerais State (CPP 124, 127, 129a, 152, 156, 197, 199, 200, 208, 216, 241, 375/1, 376, 447-449, 474, 475 ? Peirópolis locality, Uberaba municipality). This is a heterogeneous collection, with teeth ranging from 6 to 68mm in tall, wrinkles present as high-relief or as weakly marked crenulations, arched or straight in orientation, at mesial and/or distal carinae on lingual or on both sides. Such teeth also varies on the morphology of the denticles, from chisel-like (almost all) to lanceolate (CPP-127, 200, 208, 375/1, 475), and in the degree of posterior curvature of the crown, from absent to moderate. The degree of bucco-lingual compression is also quite variable. Although most teeth show fore-aft basal length around two times its basal width, some teeth (MMR/UFU-PV 005, CPP-447) have sub-rounded basal cross-section. All these teeth were previously described in the literature as Carcharodontosauridae uniquely due to the presence of wrinkles. Due to the lack of unambiguous diagnosable dental features, we consider temerarious the assignment of those Campanian-Maastrichtian teeth to a typical Cenomanian group, the Carcharodontosauridae, avoiding in this way to assume an almost 20 million years hiatus based upon so feeble evidence. Moreover, the presence of well marked wrinkles in the abelisaurid Skorpiovenator bustingorryi Canale et al. 2009 (Late Cenomanian?Early Turonian, Huincul Formation, Argentina) suggests the attribution of the re-studied teeth to Abelisauridae as a more plausible hypothesis, given the unambiguous osteological record of Abelisauridae in the Bauru Group (Novas et al., 2008).