Silesauridae

Silesaurids; Temporal range: ?Middle Triassic – Late Triassic, ?245–203 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Ornithodira
Clade:	Dinosauromorpha
Clade:	Dinosauriformes
Clade:	Dracohors
Clade:	Dinosauria
Clade:	†Ornithischia (?)
Family:	†Silesauridae; Langer et al., 2010
Subgroups
	†Agnosphitys?; †Asilisaurus?; †Ignotosaurus; †Lewisuchus?; †Pisanosaurus?; †Soumyasaurus?; †Sulcimentisauria Martz & Small, 2019 †Amanasaurus; †Diodorus?; †Eucoelophysis?; †Gamatavus?; †Gondwanax; †Kwanasaurus?; †Lutungutali?; †Sacisaurus?; †Silesaurus; †Technosaurus?; ;

Silesauridae is an extinct family of Triassic dinosauriforms. It is most commonly considered to be a clade of non-dinosaur dinosauriforms, and the sister group of dinosaurs.^[1]^[2]^[3]^[4]^[5] Some studies have instead suggested that most or all silesaurids comprised an early diverging clade or a paraphyletic grade within ornithischian dinosaurs.^[6]^[7]^[8]^[9] Silesaurids have a consistent general body plan, with a fairly long neck and legs and possibly quadrupedal habits, but most silesaurids are heavily fragmentary nonetheless. Furthermore, they occupied a variety of ecological niches, with early silesaurids (such as Lewisuchus)^[10] being carnivorous and later taxa (such as Kwanasaurus)^[11] having adaptations for specialized herbivory. As indicated by the contents of referred coprolites, Silesaurus may have been insectivorous, feeding selectively on small beetles and other arthropods.^[12]

Classification

Distribution of known silesaurids in the Early Triassic

Silesauridae is typically considered the sister group to Dinosauria. The group was named in 2010 by Max C. Langer et al. They defined it as a branch-based clade of all archosaurs closer to Silesaurus opolensis than to either Heterodontosaurus tucki or Marasuchus lilloensis.^[13] At around the same time, Sterling J. Nesbitt et al. (2010) independently named Silesauridae as a node-based clade consisting of Lewisuchus, Silesaurus, their last common ancestor and all their descendants.^[1] Currently, both definitions encompass the same group of animals. Nesbitt et al. noted that the earlier definition by Langer et al. did not include a diagnosis, and so was not sufficient to create a ranked family-level name according to the ICZN. Therefore, the family Silesauridae is attributed to Nesbitt et al. (2010) while the clade Silesauridae is attributed to Langer et al. (2010).^[3]

Phylogenetic studies originally recovered Silesauridae as a clade sister to Dinosauria, including a variety of Triassic taxa related to Silesaurus. 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 and dinosauromorphs carried out by Matthew Baron, David Norman and Paul Barrett (2017) and published in the journal Nature recovered Silesauridae as a monophyletic sister group to Dinosauria. The study also recovered the taxon Agnosphitys within the clade Silesauridae, close to Lewisuchus and its synonymous taxon Pseudolagosuchus.^[4] A 2022 study by Norman and colleagues instead found silesaurs to be a paraphyletic group on the branch leading to traditional Ornithischia. 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 and Silesaurus have still been recovered as a clade, which makes them the only members of Silesauridae under those results.^[15]

The inclusion of Pisanosaurus by some studies would mean that, according to ICZN 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]

Martz & Small, 2019^[17]