Major Issues in the Notosuchian Phylogeny: Taxon and Character Sampling

POL, DIEGO; LEARDI, JUAN MARTÍN; LECUONA, AGUSTINA; NASCIMENTO, PAULO; ZAHER, HUSSAM

San Juan

Congreso; IV Congreso Latinoamericano de Paleontología de Vertebrados; 2011

The taxonomic diversity of Cretaceous crocodyliforms from Gondwana has notably increased during the last decade. Most of these taxa have been related to Notosuchia Gasparini 1971, a large clade of basal mesoeucrocodylians that includes small-bodied taxa as well as baurusuchids, and according to some authors Araripesuchus Price 1959 and sebecids (e.g., Pol and Apesteguía, 2005). Other authors, however, consider either of the latter two taxa as more closely related to peirosaurids and/or neosuchians (e.g., Ortega et al., 2000; Larsson and Sues, 2007). In this contribution we present a phylogenetic analysis that expands the taxon and character sampling from previous studies, gathering characters stemming from previously published studies but most importantly adding 92 new characters relevant to the relationships of Cretaceous crocodyliforms from Gondwana. The new characters include 52 postcranial characters and 40 cranial characters. The incorporation of postcranial characters to the phylogenetic analysis is critical to produce a novel arrangement of the basal mesoeucrocodylians recorded in the Cretaceous–Cenozoic of Gondwana, clustering Araripesuchus and peirosaurids as sister taxa and this clade as the sister group of all other notosuchians. A large clade of basal mesoeucrocodylians with similar taxonomic content (i.e., peirosaurids, Araripesuchus, and notosuchians, including sebecosuchians) has been previously referred as Gondwanasuchia (Carvalho et al., 2004) as it clusters most of the Cretaceous crocodyliform diversity from Gondwana.The new skull and mandibular data provides high character support for the monophyly of advanced notosuchians, a clade formed by taxa found in the Late Cretaceous of South America, excluding all other notosuchians recorded in other regions of Gondwana (Africa, Madagascar). The new postcranial characters (e.g., dorsally projected and strongly curved prezygapophysis of anterior cervicals, deep circular depression on the proximal humerus for the M. scapulohumeralis caudalis, subrectangular posterior end of postacetabular process of the ilium with ventral margin horizontally directed ventrally to acetabular roof, trapezoidal fibular facet on the astragalus) incorporated in the cladistic analysis provide decisive support for monophyly of Gondwanasuchia and strengthen the affinities of Sebecidae with Baurusuchidae (sebecosuchian monophyly), as deeply nested within Notosuchia.