Silesauridae is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

dinosauriforms. It is most commonly considered to be a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

of non-dinosaur dinosauriforms, and the sister group of

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s. Some studies have instead suggested that most or all silesaurids comprised an early diverging clade or a

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

grade Grade most commonly refers to: * Grade (education), a measurement of a student's performance * Grade, the number of the year a student has reached in a given educational stage * Grade (slope), the steepness of a slope Grade or grading may also ref ...

within

ornithischian Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek st ...

dinosaurs. 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 In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for ...

, with early silesaurids (such as '' Lewisuchus'') being

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...

and later taxa (such as ''

Kwanasaurus ''Kwanasaurus'' is an extinct genus of silesaurid dinosauromorph reptiles from the Late Triassic of Colorado. It is known from a single species, ''Kwanasaurus williamparkeri''. ''Kwanasaurus'' had a deeper, stronger skull and greater specializati ...

'') having adaptations for specialized

herbivory A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

. As indicated by the contents of referred

coprolites A coprolite (also known as a coprolith) is fossilized feces. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour (in this case, diet) rather than morphology. The name is de ...

, '' Silesaurus'' may have been insectivorous, feeding selectively on small beetles and other arthropods.

Classification

Silesauridae is typically considered the sister group to

Dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

ia. The group was named in 2010 by Max C. Langer ''et al''. They defined it as a branch-based clade of all

archosaur Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avian d ...

s closer to '' Silesaurus opolensis'' than to either '' Heterodontosaurus tucki'' or '' Marasuchus lilloensis''. At around the same time,

Sterling J. Nesbitt Sterling Nesbitt (born March 25, 1982, in Mesa, Arizona) is an American paleontologist best known for his work on the origin and early evolutionary patterns of archosaurs. He is currently an associate professor at Virginia Tech in the Department of ...

''et al''. (2010) independently named Silesauridae as a node-based clade consisting of '' Lewisuchus'', ''Silesaurus'', their last common ancestor and all their descendants. 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

-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). The fossils range in age from the

Anisian In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago. The Anisian Age succeeds the Olenekian Age (part of the Lower Triassic ...

to the

Norian The Norian is a division of the Triassic Period. It has the rank of an age (geochronology) or stage (chronostratigraphy). It lasted from ~227 to million years ago. It was preceded by the Carnian and succeeded by the Rhaetian. Stratigraphic defi ...

stages of the Triassic, about 245 to 203 million years ago. The

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

below follows the

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

analysis of basal ornithodirans conducted by Christian Kammerer, Sterling Nesbitt and

Neil Shubin Neil Shubin (born December 22, 1960) is an American paleontologist, evolutionary biologist and popular science writer. He is the Robert R. Bensley Professor of Organismal Biology and Anatomy, Associate Dean of Organismal Biology and Anatomy and ...

(2012) with clade terminology from Cau (2018) and Martz and Small (2019). 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 Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...

'' recovered Silesauridae as a

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

sister group to Dinosauria. The study also recovered the taxon ''

Agnosphitys ''Agnosphitys'' (; "unknown begetter"; sometimes mistakenly called ''Agnostiphys'' or ''Agnosphytis'') is a genus of dinosauriform that lived during the Late Triassic. It contains only one species, the type species ''A. cromhallensis''. Its remai ...

'' within the clade Silesauridae, close to '' Lewisuchus'' and its synonymous taxon ''

Pseudolagosuchus ''Lewisuchus'' is a genus of archosaur that lived during the Late Triassic (early Carnian). As a silesaurid dinosauriform, it was a member of the group of reptiles most commonly considered to be the closest relatives of dinosaurs (possibly tr ...

''.

References

External links

Silesauridae
in the Paleobiology Database Prehistoric reptile families Anisian first appearances Rhaetian extinctions {{triassic-reptile-stub