A New Notosuchian from the Late Cretaceous of Brazil and the Phylogeny of Advanced Notosuchians

Abstract

A new notosuchian crocodyliform from the Late Cretaceous Bauru Group found in the southeastern State of São Paulo (Brazil) is described here. The new taxon, Caipirasuchus stenognathus, is referred as a new species of the recently erected genus Caipirasuchus within the clade Sphagesauridae based on a phylogenetic analysis of basal mesoeucrocodylians. Caipirasuchus stenognathus is represented by an almost complete skull and lower jaw that has autapomorphic characters that distinguish it from other species of Sphagesauridae. These autapomorphies include: maxilla forming part of the orbital margin (absence of lacrimal-jugal contact), nasal with smooth depressions on the posterior region close to the contact with the maxilla and lacrimal, postorbital with posterior palpebral facet that extends posteriorly underneath the ear-flap groove, and a distinct anterior process of the medial flange of the retroarticular process. Additionally, the new taxon lacks autapomorphic features described in other sphagesaurids. The phylogenetic analysis results in a monophyletic genus Caipirasuchus, that is the sister group of a clade fomed by Sphagesaurus huenei, Caryonosuchus pricei, and Armadillosuchus arrudai. Sphagesaurids also include a basal clade formed by Adamantinasuchus navae and Yacarerani boliviensis. Other notosuchian taxa, such as Mariliasuchus amarali, Labidiosuchus amicum, Notosuchus terrestris, and Morrinhosuchus luziae are successive sister taxa of Sphagesauridae, forming a clade of advanced notosuchians that are restricted to the Late Cretaceous of South America. These results contrast with most previous phylogenetic hypotheses of the group that depicted some members of Sphagesauridae as more closely related to baurusuchids, or found Asian (e.g., Chimaerasuchus) or African (Malawisuchus, Pakasuchus) forms nested within advanced notosuchians that are, according to our analysis, endemic of the Late Cretaceous of South America.

Reptiles Extintos - Volumen en Homenaje a Zulma Gasparini

“…NOTOSUCHIA is the most diverse clade of Gondwanan crocodyliforms that thrived during the Cretaceous Period (Turner and Sertich, 2010;Pol et al, 2014 and five taxa from the Cretaceous of Brazil (Price, 1945(Price, , 1950a(Price, ,b, 1955(Price, , 1959 Price, 1950aPrice, ,b, 1955.…”

“…One of the most relevant contributions was the creation of Notosuchia (Gasparini, 1971) (Gasparini, 1972) and Peirosauridae (Gasparini, 1982), which were not considered part of Notosuchia until recently Pol, 2003;Turner and Sertich, 2010;Pol and Powell, 2011;Pol et al, 2012Pol et al, , 2014 (Gasparini, 1982) by recognizing the distinctness of Peirosaurus torminni from all other crocodyliforms, while studying the type materials of this taxon described originally by Price (1955), and more complete material discovered in Patagonia. These studies therefore organized the known diversity of Cretaceous crocodyliforms from South America by recognizing four basic groups: Notosuchidae, Uruguaysuchidae, Peirosauridae, and Baurusuchidae.…”

“…The new discoveries, coupled with the inclusion of both Baurusuchidae and Peirosauridae within Notosuchia in recent phylogenetic studies (e.g., Turner and Sertich, 2010;Pol et al, 2012Pol et al, , 2014, revealed a previously unsuspected diversity of Notosuchian crocodyliforms. There has been an almost 4-fold increase in its known diversity during the last 25 years (Fig.…”

“…A strong component of recent research on notosuchians has been the use of cladistics analysis for testing the relationships of Notosuchia Pol, 2003;Carvalho et al, 2004;Turner and Sertich, 2010;Andrade et al, 2011;Montefeltro et al, 2011;Pol et al, 2012Pol et al, , 2014. Many of these studies are now corroborating the monophyly of the four Cretaceous clades early recognized by Gasparini for South American forms in pioneer contributions during her early career (i.e., Uruguaysuchidae, Peirosauridae, Baurusuchidae, and a clade allying Notosuchus and closely related forms; Gasparini, 1971Gasparini, , 1972Gasparini, , 1982.…”

“…The systematic arrangement of notosuchian species was based on recent phylogenetic analyses published by Pol et al (2014), with subsequent addition of two taxa made by Leardi et al (2015). These studies were chosen as they are the most comprehensive analyses, in terms of both taxon and character sampling, of notosuchian crocodyliforms performed to date and agree in many aspects with other studies published in recent years (Sereno and Larsson, 2009;Turner and Sertich, 2010;Andrade et al, 2011;Montefeltro et al, 2013;Sertich and O'Connor, 2014).…”