New Species of Plotopteridae (Aves) from the Oligocene Ashiya Group of Northern Kyushu, Japan

Abstract

Four coracoids belonging to the family Plotopteridae have been found from the Oligocene Ashiya Group, northern Kyushu, Japan. One coracoid is assigned to Copepteryx hexeris, and the other coracoids are assigned to new genera and species: Stenornis kanmonensis gen. et sp. nov., and Empeirodytes okazakii gen. et sp. nov., of the Plotopteridae. Stenornis and Empeirodytes share a synapomorphy: an elongate sulcus on the ventral surface of the facies articularis humeralis portion of the shaft, which is not observed in coracoids of other plotopterids. These new plotopterids reveal that the diversity of this group in the Oligocene Ashiya Group is higher than previously realized.