A Coelophysoidea (Dinosauria, Theropoda) femur from the Tytherington fissures (Rhaetian, Late Triassic), Bristol, UK

Abstract

Theropods originated in the Late Triassic and their relations and early evolution are still topics of discussion. Within Neotheropoda, coelophysoids represent their earliest worldwide radiation and include most Triassic theropods, but their internal relations remain volatile. In this paper, we discuss the significance of a coelophysoid femur from the Rhaetian Tytherington fissures near Bristol, UK. The specimen belongs to a small-sized individual and is complete, but for the fourth trochanter blade. The most distinctive aspects of the femur are a sharply pointed lateral condyle and the pentagonal distal outline. The features that supposedly correlate with ontogenetic development, in addition to several well-developed scars, indicate it probably pertains to a mature individual. Its inclusion in a taxon-character matrix recovered the specimen within Coelophysoidea, but created a polytomy encompassing all members of the group. A definitive referral of the femur to the previously recorded coelophysoid Pendraig milnerae is precluded by the lack of overlap in diagnostic anatomical parts, the paucity of specimens from the Bristol Channel Triassic fissures, and the possible geological age difference between them.