?CHASMATOSAURUS ULTIMUS,? A PUTATIVE PROTEROSUCHID ARCHOSAURIFORM FROM THE MIDDLE TRIASSIC, IS AN INDETERMINATE CROWN ARCHOSAUR

LIU, J.; BUTLER, R. J.; SULLIVAN, C.; EZCURRA, M. D.

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Lugar: Lawrence; Año: 2015

0272-4634

Proterosuchids represent the earliest known radiation of thehighly diverse and important clade Archosauriformes (Gauthieret al., 1988; Nesbitt, 2011; Ezcurra et al., 2013). Huene (1908)erected Proterosuchidae as a monotypic Linnean family containingonly Proterosuchus fergusi from the lowermost Triassic ofSouth Africa, and several other species have been referred tothis group in the subsequent century. However, phylogeneticanalyses have provided only partial support for the existence of adiverse proterosuchid clade, and it is possible that some or evenmost putative proterosuchids form a series of outgroups to morederived archosauriforms rather than a monophyletic group(Ezcurra et al., 2010, 2013). Proterosuchids were historicallyclassified alongside erythrosuchids in the Proterosuchia (e.g.,Charig and Reig, 1970), but cladistic analyses (e.g., Benton,1985; Gauthier et al., 1988; Gower and Sennikov, 1997; Ezcurraet al., 2010; Nesbitt, 2011) have uniformly found erythrosuchidsto be phylogenetically closer to Archosauria (using a crowngroupdefinition for the clade) than are any putative proterosuchids.Many of the species that have been assigned to Proterosuchidaerequire anatomical and taxonomic reevaluation (e.g.,Ezcurra et al., 2010, 2013, 2014; Ezcurra, 2014), a research effortthat is essential in order to clarify the phylogenetic relationshipsof the earliest archosauriforms and patterns of character evolutionin taxa of this grade.