The diverse Cretaceous neobatrachian fauna of South America: A new record from the Maastrichtian Marília Formation at Uberaba, Minas Gerais, Brazil

BÁEZ, A.M.; GÓMEZ, R.O.; RIBEIRO, C.B.; MARTINELLI, A.G.

San Juan

Congreso; IV Congreso Latinoamericano de Paleontología de Vertebrados; 2011

Instituto y Museo de Ciencias Naturales, Universidad Nacional de San Juan, San Juan, Argentina

Neobatrachians, which are distributed worldwide and occupy a wide variety of environments today, constitute the most derived and diverse clade of extant anurans. Their oldest known records date back to the mid-Cretaceous of South America and document an early diversification by that time (Báez et al., 2009). However, neobatrachian remains are still scarce throughout the rest of the Mesozoic, mainly consisting of isolated bones of Senonian age. The articulated materials from the Upper Cretaceous of Brazil, such as those from the Adamatina (Carvalho et al., 2003) and Marília (Báez & Perí, 1989) formations, constitute outstanding exceptions. Herein we report on a new frog (Centro de Pesquisas Paleontologicas L.I. Price [CPP] 1115) from the latter stratigraphic unit at the well-known paleontological site “Ponto 1 do Price” near Peirópolis, Uberaba, Minas Gerais State, which has also yielded a diverse vertebrate assemblage (e.g., Novas et al., 2008). The age of these fossiliferous beds has been considered Maastrichtian based on microfossils (Dias-Brito et al., 2001). The specimen CPP1115 consists of an articulated partial skeleton characterized by a broad, well-ossified skull without dermal ornamentation, eight procoelous presacrals, and posteriorly deflected, cylindrical sacral diapophyses; these features, together with the possible presence of a discrete palatine, are consistent with neobatrachian affinities. It clearly differs from the neobatrachian Baurubatrachus Báez and Perí, 1989, also from the Marília Formation, in having a skull without exostosis and with a different temporal architecture, among other features. It also differs from the unnamed Campanian-Mastrichtian neobatrachian from the Adamatina Formation (Carvalho et al., 2003) in the presence of paired frontoparietals with small supraorbital flanges in the mid-orbital region and maxilla-squamosal contact. The new material is not referable to any of the neobatrachian taxa of the Aptian-Albian Crato Formation (Báez et al., 2009) owing to different cranial features (e.g., position of the jaw articulation; relative width of the braincase; morphology of the frontoparietal). With respect to the extant neobatrachians in the context of recent phylogenetic hypotheses, the cylindrical sacral diapophyses of CPP1115 contrast with the dilated configuration of australobatrachian hyloids and microhyloid ranoids, whereas the procoelous presacral column is unlike the diplasiocoelous condition of most other ranoids. This evidence together with the combination of features of CPP1115 suggests a placement among nobleobatrachians, although this combination is not shared with any extant or extinct species for which the skeletal information is known. From the foregoing we conclude that CPP1115 might represent a new nobleobatrachian taxon, a record that reinforces the hypothesis of a diversified neobatrachian fauna in South America already in the Cretaceous (Báez et al., 2009).