Ontogenetic changes in hind limb proportions within the Ghost Ranch population of Coelophysis bauri

Describes how changes in bone sutures provide a key to growth changes in Coelophysis.

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Ontogenetic stages (juvenile, subadult, and adult) of individuals from the Coelophysis bauri population of Ghost Ranch quarry were defined by relative degree of suture closure. Even though the ontogenetic series is incomplete (lacking in very young and very old individuals), the size variation was substantial with increases of a factor of 2.3 in femora length and 3.6 in skull length.

Ceratosaurs have been characterized as possessing dimorphic (gracile and robust) characters that are present predominantly in adults. Principle components analysis of hind limb measurements of Coelophysis indicates that there is no separation of individuals into dimorphic groups, which concurs with subjective physical examination of the skeletons.

Hind limb proportions varied with ontogenetic stage, which may reflect changing locomotor need of the animals during ontogeny. Overall locomotor ability was assessed using possible ranges of joint movement and limb bone proportions. Coelophysis appears to have been a relatively rapid and efficient runner.