Distribution of known silesaurids in the Early Triassic
Silesauridae is typically considered thesister group toDinosauria. The group was named in 2010 byMax C. Langeret al. They defined it as a branch-based clade of allarchosaurs closer toSilesaurus opolensis than to eitherHeterodontosaurus tucki orMarasuchus lilloensis.[13] At around the same time,Sterling J. Nesbittet al. (2010) independently named Silesauridae as a node-based clade consisting ofLewisuchus,Silesaurus, their last common ancestor and all their descendants.[1] Currently, both definitions encompass the same group of animals. Nesbittet al. noted that the earlier definition by Langeret al. did not include a diagnosis, and so was not sufficient to create a rankedfamily-level name according to theICZN. Therefore, the family Silesauridae is attributed to Nesbittet al. (2010) while the clade Silesauridae is attributed to Langeret al. (2010).[3]
Phylogenetic studies originally recovered Silesauridae as a clade sister toDinosauria, including a variety of Triassic taxa related toSilesaurus. Sometimes the genera are recovered as successive sister taxa to dinosaurs rather than a clade, but often a group is recovered as possibly quadrupedal herbivorous taxa.[13]
A large phylogenetic analysis of early dinosaurs anddinosauromorphs carried out by Matthew Baron,David Norman and Paul Barrett (2017) and published in the journalNature recovered Silesauridae as amonophyletic sister group to Dinosauria. The study also recovered the taxonAgnosphitys within the clade Silesauridae, close toLewisuchus and itssynonymous taxonPseudolagosuchus.[4] A 2022 study by Norman and colleagues instead found silesaurs to be aparaphyletic group on the branch leading to traditionalOrnithischia. The cladogram below is based on their study.[14] This topology is almost identical to the one recovered by Müller & Garcia (2020)[9] in their first iteration of the same dataset. When found as a grade of ornithischians,Amanasaurus,Ignotosaurus andSilesaurus have still been recovered as a clade, which makes them the only members of Silesauridae under those results.[15]
The inclusion ofPisanosaurus by some studies would mean that, according toICZN rules, the name of the family should be the older name,Pisanosauridae, which was erected by Rodolfo Casamiquela in 1967.
While Sulcimentisauria is used for all ornithischians by some authors, the original intention of the clade was as a subdivision within Silesauridae, the new use being significantly different from its original application. A solution to this could be to restrict Sulcimentisauria to only apply to a subclade of Silesauridae, where it would no longer be applied along the ornithischian stem as a clade.[16]
^Ferigolo, Jorge; Langer, Max C. (1 January 2007). "A Late Triassic dinosauriform from south Brazil and the origin of the ornithischian predentary bone".Historical Biology.19 (1):23–33.doi:10.1080/08912960600845767.ISSN0891-2963.S2CID85819339.
