New Mexico Geological Society Annual Spring Meeting — Abstracts

Furculae were known only in birds throughout much of the history of biology and paleontology. However, furculae have now been identified in many dinosaurs and are considered to be synapomorphic in some groups (e.g., dromeosaurids). All coelophysid dinosaurs except Coelophysis bauri have previously been shown to possess furculae. To date, the oldest documented furculae have been those of the Early Jurassic coelophysids, Coelophysis kayentakatae (= Syntarsus kayentakatae = Megapnosaurus kayentakatae) and Coelophysis rhodesiensis (= Syntarsus rhodensiensis = Megapnosaurus rhodesiensis). Now, a total of five C. bauri furculae have been found in the New Mexico Museum of Natural History’s (NMMNH) Ghost Ranch, New Mexico Whitaker Quarry block C-8-82. Three of the furculae are articulated in juvenile skeletons; two of these are missing fragments but are nearly complete, and one is apparently complete. A small fragment of a furcula associated with an adult C. bauri, and one complete but isolated furcula, are also described. The furculae have epicledial facets for articulation to the acromion processes of the scapulae and some show a ventromedian process (hypocleidium) that articulates to the (apparently cartilaginous) sternum. Using accurate measurements of the scapulocoracoid and furcula we reconstruct the complete shoulder girdle of C. bauri with proper spacing and angles between the elements for the first time. The discovery of furculae in Apachean-aged C. bauri pushes the first appearance of these elements back to the Late Triassic and shows that furculae are synapomorphic in the Coelophysidae. One implication of furculae in these basal theropods is that the presence of a furcula may be synapomorphic for the Dinosauria.