First record of a tarsometatarsus of Tonsala hildegardae (Plotopteridae) and other avian remains from the late Eocene/early Oligocene of Washington State (USA)

New bird fossils from the late Eocene/early Oligocene Makah Formation and the Oligocene Pysht Formation on the Olympic Peninsula (Washington State, USA) are described. A partial skeleton from the Pysht Formation includes the first reported tarsometatarsus of Tonsala hildegardae Olson, 1980, a wing-propelled diving bird of the taxon Plotopteridae. It shows that Tonsala had a tarsometatarsus that was morphologically intermediate between that of the late Eocene Phocavis and more derived plotopterids. We introduce the new taxon Tonsalinae nov. subfam. for a clade including all named plotopterids except Phocavis, Plotopterum, and the recently described Stemec. We furthermore describe a partial plotopterid pelvis and a sternum from the Makah Formation. The sternum shows a close resemblance to that of extant Phalacrocoracoidea (cormorants and darters) and may be the earliest North American record of this taxon.