Triassic Late Carnian Norian
Saurischia Theropoda Ceratosauria Podokesauridae
Genus - Skull
Coelophysis (Cope, 1889) = Rioarribasaurus (Hunt & Lucas, 1991)
Coelophysis bauri (Cope, 1889) = Coelurus bauri (Cope, 1887) [Rioarribasaurus bauri] (Cope, 1887) [Tanystrophaeus bauri] (Cope, 1887) Rioarribasaurus colberti (Hunt & Lucas, 1991) [Syntarsus colberti] (Hunt & Lucas, 1991)
Coelophysis bauri is the best-represented Triassic theropod (Colbert, 1989, 1990), although it has been the center of debate over the diagnosability of its original material and its relationship to theropod material from the prolific Ghost Ranch Quarry locality (Padian, 1986; Hunt and Lucas , 1991). Hunt and Lucas, (1991) urged restricting the name to the original material and proposed a new name for the Ghost Ranch theropods, Rioarribasaurus colberti. However the ICZN was petitioned to erect a neotype (Colbert et al. , 1992), which it did (ICZN, 1996). All the coelophysids from the Ghost Ranch locality are now considered Coelophysis bauri. Surprisingly, this well-known theropod has not been diagnosed by unique apomorphies and is currently a metataxon that posseses only characters shared with Coelophysidae.
Fragmentary remains of a small theropod were collected from the Chinle Formation, near the Ghost Ranch locality, and were proposed to be a new taxon distinct from Coelophysis (Sullivan & Lucas, 1999). The material represents a juvenile or subadult and cannot be unequivocally diagnosed from other coelophysoids. Two specimens from the Connecticut Valley (eastern US), probably from the Portland Formation (Lower Jurassic) were assigned to Coelophysis. One was composed solely of the lost specimen of Podokesaurus holykensis (Talbot, 1911). Colbert (1964) referred this specimen to Coelophysis (C. holyokensis) on the basis of what can now be seen as shared plesiomorphic features.
While Podokesaurus may psosses coelophysoid characters, it preserves no derived characters uniting it with Coelophysis. The name Podokesaurus holyokensis is regarded to be restricted to the lost specimen.
The second specimen may be coelophysoid but it posseses no characters diagnosable beyond the level of Theropoda.
Tykoski & Rowe, 2004
Several hundred individuals, juvenile to adult, including nearly complete articulated skeletons. One of the earliest well-known dinosaurus, Coelophysis ("hollow form") was a flesheater, built like a large, slender bird, with a narrow, alomst stork-like head, an S-shapped neck, a slim body, and long, bird-like legs.
Some internal features were also bird-like, including hollow thinwalled bones, and the fusion of bones at the hips and spine, as well as those of the ankles and upper feet. Coelophysis was a very common little hunter of the Late Triassic. It came in two forms, 'robust' and 'gracile'. These are thought to represent the two sexes.
The type specimen of Coelophysis bauri is a deficient specimen that preserves no diagnostic attributes beyond those of Theropoda ancestrally (Padian, 1986). However, im lieu of data to the contrary, we follow the convention of using this name for the large sample from Ghost Rance, New Mexico as well as material from Petrified Forest, National Park, Arizona.
Several hundred individuals of Coelophysis bauri have now been recovered from the Ghost Ranch Quarry and they include a range of ontogenetic stages from young juveniles to adults of both robust and gracile morphs. However, even with this large sample Coelophysis, like Liliensternus, is yet undiagnosed.
Two exelent preserved specimens AMNH 7223 and AMNH 7224 in which a juvenile skeleton of this species was apparently preserved whitin the abdominal cavity of the adult are often taken as provenance that this theropod engaged in cannibalism, however Gay (2002) suggested that the occurence of the juvenile skeleton whitin the body cavity of the adult may be better explained by taphonomy rather than behavior.
Observations cited by Gay: In some area, both left and right ribs of the adult overlay the smaller skeleton, showing that the juvenile is in fact, underneath rather than inside the older individual. Volumetric analysis of the bones found whitin the adult chest cavity (soft tissue not taken into account) further indicate that the elements "would take up the maximum possible stomach size for this animal. Also some bones belonging to the allegedly canabilized juvenile would be difficult for the adult to ingest.
Nesbitt, S., Turner, A. & Erickson, G. (2006) Digesting the Coelophysis-cannibal hypothesis and its importance to prey choice in Theropod dinosaurs. JVP 26(3) Abstracts pp.105
Direct evidence of prey choice in carnivorous dinosaurs is rare in the fossil record. The most celebrated example pertains to purported stomach contents in two specimens of the early carnivorous dinosaur Coelophysis bauri (AMNH FR 7223 and AMNH FR 7224), which besides revealing prey choice, also point to cannibalistic behavior as being commonplace among theropod dinosaurs.
The Coelophysis-cannibal hypothesis is one of the most recognized paleobiological anecdotes presented in museum exhibitions, countless children’s books, and in popular press. Here, we test this hypothesis by conducting the first comprehensive anatomical and histological examination of the famed Coelophysis cannibals.
Reinspection of AMNH FR 7223 revealed that the ribcage ruptured sometime during burial and that the purported remains lie underneath the Coelophysis skeleton. Thus, no unambiguous stomach contents are present in AMNH FR 7223. The stomach remains in AMNH 7224 lie within the posterior region of the intact ribcage. The stomach contents include an ilium, left and right femora, a sacral vertebra, and many additional fragments.
None of the stomach remains bear dinosaurian synapomorphies. Instead, the elements bear character states consistent with crocodylomorph archosaurs. The preserved femur has a proximal condylar fold, which is synapomorphic for Crocodylomorpha. Morever, histological analysis of the femur supports assignment to Crocodylomorpha rather than a Theropoda.
The results unequivocally show that the gut contents derive from early crocodylomorphs rather than juveniles of Coelophysis. These findings exonerate this taxon as being cannibalistic and bring into question the commonality of this behavior among non-avian dinosaurs.
Taxonomic placement by Nesbitt, S.J., Irmis, R.B. and Parker, W.G. (2007): A valid taxon and basal member of the Neotheropoda.