second clade with a similar definition, Crocodylotarsi, was named in 1988, possibly as a replacement for Pseudosuchia. The name Pseudosuchia, meaning "false crocodiles", has been used for over a century, and traditionally included only aetosaurs, but when defined as a clade, Pseudosuchia came to include the group Eusuchia ("true crocodiles") as well. Crocodylotarsi may have been named to remove confusion, but as a stem-based clade, it is synonymous with Pseudosuchia. Because Pseudosuchia was named first, it has precedence. A third group, Crurotarsi, traditionally included the same archosaurs as Pseudosuchia, but as a node-based clade it is not synonymous. The scope of Crurotarsi has recently been changed by the phylogenetic placement of phytosaurs. In 2011, Sterling J. Nesbitt found phytosaurs to be the sister taxon of Archosauria, and therefore not crocodile-line archosaurs. Because phytosaurs are included in the definition of Crurotarsi, crurotarsans are not solely crocodile-line archosaurs, but also bird-line archosaurs and phytosaurs. Under this phylogeny, Crurotarsi includes phytosaurs, crocodiles, pterosaurs, and dinosaurs, while Pseudosuchia still contains only crocodile-line archosaurs. Below is a cladogram modified from Nesbitt (2011) showing the new changes (bold terminal taxa are collapsed). The following cladogram is from a slightly older study, Brusatte, Benton, Desojo and Langer (2010). Bold terminal taxa are collapsed. Several results of the study, such as the retention of a monophyletic Rauisuchia, the retention of phytosaurs within Pseudosuchia, and a close relation between aetosaurs and crocodylomorphs, replicate the results of older studies. However, the findings of Nesbitt (2011) have been more widely supported by pseudosuchian-focused analyses published since 2011. References Sources Sereno, P. C. 2005. Stem Archosauria—TaxonSearch [version 1.0, 7 November 2005] External links Taxon Search – Pseudosuchia Re: Even more last papers for 2005 and follow up posts, on the Dinosaur Mailing List archives, for comments critical of applying "Pseudosuchia" in a cladistic context. Extant Early Triassic first appearances