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Furculae in the Late Triassic theropod dinosaur Coelophysis bauri

Describes several well-preserved examples of wishbones (furculae) in a block of Coelophysis skeletons from the Ghost Ranch bonebed.

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Abstract

Furculae have been identified in many dinosaurs and are synapomorphic in some clades (e.g., dromaeosaurids). All coelophysid dinosaurs except Coelophysis bauri have been shown to possess furculae. To date, the oldest well-documented furculae have been those of the Early Jurassic coelophysids, Coelophysis kayentakatae and Coelophysis rhodesiensis. The confirmation of furculae in Apachean-aged C. bauri further documents appearance of these elements in the Late Triassic and shows that furculae are synapomorphic in the Coelophysidae. A total of five furculae have been found in New Mexico Museum of Natural History's (NMMNH) Ghost Ranch, New Mexico Whitaker Quarry block C-8-82. We describe three furculae in articulated juvenile skeletons; two that are missing fragments but are nearly complete, and one apparently complete, a small fragment of a furcula associated with an adult C. bauri, and one complete but isolated furcula. We access the morphology and allometry of the scapulocoracoid and furcula and show that they grow, at least in juveniles, in isometry with the humerus. The furcula of C. bauri has a widely opened U shape that subtends an angle of ~120 degrees. All the furculae have groove-like epicleidial facets at the distal ends of the rami and some possess a small centrally located hypocleideal process. We reconstruct the complete shoulder girdle of C. bauri with proper spacing and angles between the elements and find that the coracoids are very close together under the center of the furcula.