Coelophysoidea were common

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 ...

s of the Late

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 ...

and Early Jurassic periods. They were widespread geographically, probably living on all continents. Coelophysoids were all slender,

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 so ...

forms with a superficial similarity to the

coelurosaur Coelurosauria (; from Greek, meaning "hollow tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, tyran ...

s, with which they were formerly classified, and some species had delicate cranial crests. Sizes range from about 1 to 6 m in length. It is unknown what kind of external covering coelophysoids had, and various artists have portrayed them as either scaly or feathered. Some species may have lived in packs, as inferred from sites where numerous individuals have been found together. Examples of coelophysoids include '' Coelophysis'', ''

Procompsognathus ''Procompsognathus'' is an extinct genus of coelophysid theropod dinosaur that lived approximately 210 million years ago during the later part of the Triassic Period, in what is now Germany. ''Procompsognathus'' was a small-sized, lightly buil ...

'' and '' Liliensternus''. Most dinosaurs formerly referred to as being in the dubious taxon "Podokesauridae" are now classified as coelophysoids.

Classification

Despite their very early occurrence in the

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

, coelophysoids have a number of derived features that separate them from primitive (basal)

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

s. Among the most prominent of these derived features (''apomorphies'') is the way the upper jaw bones are connected (the

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

articulation), which is flexible with a deep gap between the teeth in the two bones. A major source of disagreement among theropod experts is whether or not coelophysoids shared a more recent common ancestor with

Ceratosauria Ceratosaurs are members of the clade Ceratosauria, a group of dinosaurs defined as all theropods sharing a more recent common ancestor with ''Ceratosaurus'' than with birds. The oldest known ceratosaur, '' Saltriovenator'', dates to the earliest ...

(''sensu stricto'') than the ceratosaurs did with other theropods. Most recent analyses indicate the latter, that Coelophysoidea does not form a natural group with the ceratosaurians. Similarly, while ''

Dilophosaurus ''Dilophosaurus'' ( ) is a genus of theropod dinosaurs that lived in what is now North America during the Early Jurassic, about 193 million years ago. Three skeletons were discovered in northern Arizona in 1940, and the two best preserve ...

'' and similar theropods have traditionally been classified as coelophysoids, several studies published in the late 2000s suggested that they may actually be more closely related to the tetanurans.Smith, N.D., Makovicky, P.J., Pol, D., Hammer, W.R., and Currie, P.J. (2007). "The dinosaurs of the Early Jurassic Hanson Formation of the Central Transantarctic Mountains: Phylogenetic review and synthesis." In Cooper, A.K. and Raymond, C.R. ''et al.'' (eds.), ''Antarctica: A Keystone in a Changing World––Online Proceedings of the 10th ISAES'', USGS Open-File Report 2007-1047, Short Research Paper 003, 5 p.; . 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 ...

below was recovered in a study by Matthew T. Carrano, John R. Hutchinson and Scott D. Sampson, 2005. The

below was recovered in a study by Martin D. Ezcurra and Gilles Cuny, 2007. The cladogram below was recovered in a study by Ezcurra ''et al''. (2020).

References

Sources

* Rauhut and Hungerbuhler (2000). "A review of European Triassic theropods." ''Gaia'', 15: 75-88. * Tykoski, R. S. (2005). "Anatomy, Ontogeny, and Phylogeny of Coelophysoid Theropods." Ph. D dissertation. * Yates, A.M., 2006 (for 2005). "A new theropod dinosaur from the Early Jurassic of South Africa and its implications for the early evolution of theropods." ''Palaeontologia Africana'', 41: 105-122. {{Taxonbar, from=Q14414 Late Triassic dinosaurs Early Jurassic dinosaurs Norian first appearances Early Jurassic extinctions

Classification

See also

References

Sources