A new species of Threskiornithidae-like bird (Aves, Ciconiiformes) from the Green River Formation (Eocene) of Wyoming

ABSTRACT A new avian species from the late early Eocene Fossil Butte Member of the Green River Formation is described based on a nearly complete postcranial skeleton. The new species, Vadaravis brownae, gen. et sp. nov., can be diagnosed by a unique combination of characters, including the following autapomorphies, which are unique among Aves: two (cranial and caudal) small and discrete pneumatopores on the lateral sides of the caudal-most thoracic centra; and a caudoventrally located pisiform process of the carpometacarpus that projects only weakly cranially. Phylogenetic analyses recover Vadaravis as a member of the waterbird assemblage (including, e.g., penguins, storks, pelicans), closely related to taxa traditionally placed within the avian order Ciconiiformes (storks, flamingos, herons, the hamerkop, ibises, and spoonbills). Additional morphological features and a phylogenetic analysis constrained by a recently recovered waterbird topology suggest close affinities between Vadaravis and Threskiornith...