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Eukaryota : Metazoa : Bilateria : Deuterostomia : Vertebrata : Tetrapoda : Diapsida : Archosauria : Dinosauria : Theropoda

Coelurosauria

Coelurosaur
Coelurosaur mount at the Mesa Southwest Museum, Mesa, AZ.
 

The phylogeny of this group of theropods is debated by paleontologists involved in its study, and new classifications are proposed several times a year! It is both a frustrating and exciting area of research.

Current coelurosaur classification

Compsognathus
One of the UCMP's casts of Compsognathus, from the Solnhofen limestone
 
Coelurosauria is defined as the clade containing all theropods more closely related to birds than to Allosaurus. Some diagnostic characteristics of coelurosaurs include elongated arms and well- developed hinge-like ankles (possible rotation of the ankle is reduced, which is helpful during locomotion). These features may be lost or modified by later coelurosaurs (birds, for example).

All coelurosaurs show a great number of morphological similarities with birds, but different coelurosaurs lack different bird-like characteristics, so this complicates the matter of resolving the phylogeny of the group.

Two examples of this problem are the very bird-like Compsognathus longipes (shown at right) and Ornitholestes hermanni, small theropods known from good specimens, but whose phylogenetic affinities have not been well resolved yet, because they share some features that might closely unite them with a group, but then lack some features that are considered diagnostic for that group. At this point they are considered incertae sedis;in other words, we know that they are theropods; and probably coelurosaurs; but we don't know who they are related to or how they fit into the big picture of theropod phylogeny.

Major coelurosaurian groups

Maniraptora: Velociraptor, birds, and other coelurosaurs
Ornithomimidae: The bird-mimic coelurosaurs
Tyrannosauridae: The giant coelurosaurs
 

Original page created by John Hutchinson 11/1995; modifications since 2005 by David Smith. Coelurosaur photo © Geb Bennett.