A Preliminary Report on the Diversity and Stratigraphic Distribution of the Plotopteridae (Pelecaniformes) in Paleogene Rocks of Washington State, USA

摘要

Late Eocene and Early Oligocene marine strata in western Washington continue to yield new fossils of the extinct, penguin-like pelecaniform family Plotopteridae. Preliminary study indicates that at least five different taxa appear to be present, and four of these may be new genera and/or species. A skeleton from the Late Eocene part of the Makah Formation near Whiskey Creek, along the north side of the Olympic Peninsula is the earliest record of the Plotopteridae. Also of Late Eocene age is a large vertebra and fragment of a scapula (?) of a plotopterid from the lower part of the Lincoln Creek Formation on the south side of the Olympic Mountains. Two different plotopterids have been found in the olistostromal Jansen Creek Member of the Makah Formation, of earliest Oligocene age. The largest of these is similar in size to the larger plotopterids from Japan, and the smaller one is nearly twice the size of Tonsala hildegardae Olson, 1980. The geochronologically youngest plotopterids from Washington are from the Early Oligocene, lower part of the Pysht Formation. These include T. hildegardae, the smallest plotopterid from Washington, and a much larger undescribed plotopterid. New specimens of T. hildegardae include, for the first time, the pelvis, femur, tibiotarsus, fibula, and mandible. Plotopterids have not yet been detected in Late Oligocene (or younger) rocks in Washington, despite the abundance of other marine vertebrates.