An enantiornithine bird from the Campanian Kaiparowits Formation of Utah, USA

An isolated coracoid represents the first described occurrence of an enantiornithine bird from the Kaiparowits Formation (Upper Cretaceous) of southern Utah, USA. The specimen is identified as enantiornithine by the convex scapular facet, approximate alignment of this facet with the humeral articular facet and acrocoracoid process, and the presence of an acrocoracoidal tubercle. This coracoid came from a comparatively large individual, consistent with previous reports of other large enantiornithines from strata of Campanian strata in North America, South America, and Europe. The occurrence of enantiornithines in the Kaiparowits Formation and their apparent absence in the well-sampled Dinosaur Park Formation of similar age in Alberta represents yet another faunal difference between the two areas, although this may be a result of environmental differences rather than the endemism proposed for non-avian dinosaurs.