Article: A crown-group galliform bird from the Middle Eocene Bridger Formation of Wyoming
Despite an extensive described fossil record of Galliformes (Aves: 'landfowl'), very few specimens have been considered within a phylogenetic context. Here we present a cladistic analysis and description of a new, well-preserved and well-dated fossil specimen from the Middle Eocene Bridger Formation of Wyoming (c. 50 Ma). Amitabha urbsinterdictensis gen. et. sp. nov. is assigned to Galliformes on the basis of the presence of derived characters including double, and open, incisurae laterales on the sternum and an incisura capitis of the proximal humerus that is enclosed from the crus dorsale fossa by a distinct ridge. Amitabha is considered to be a member of the large and diverse 'phasianoid' clade of Galliformes (including, for example, the pheasants, peafowl and turkeys) owing to a lack of extensive pneumaticity in the sternal plate. The age of this avian taxon and degree of preservation allow for a discussion of the use of fossil birds for the calibration of 'molecular clock' hypotheses and dating divergences within Neornithes in general, and Galliformes in particular.