Tonsala is an extinct genus of Plotopteridae, a family of flightless seabird similar in biology with penguins, but more closely related to modern cormorants. The genus is known from terrains dated from the Late Oligocene of the State of Washington and Japan.
History and Etymology In 1979, Storrs L. Olson and Hasegawa Yoshikazu identified several fossilized specimens of Late Oligocene and Early Miocene birds found in the State of Washington and in Japan as members of the family Plotopteridae, but distinct enough from Plotopterum in their general anatomy to warrant their own genus. The Washington fossils, collected by Douglas Emlong in Late Oligocene terrains of the Pysht Formation, in the north of the Olympic Peninsula, were formally described the next year, 1980, by Olson himself, as the type of the new genus and species Tonsala hildegardae. Olson ascribed to the genus the holotype USNM 256518, an incomplete specimen comprising a fragmentary humerus, fragments of a distal wing, a patella and a pectoral girdle. In 1996, while describing Copepteryx, Olson and Hasegawa tentatively assigned a 16.5 cm coracoid from the late Oligocene of Hikoshima, Japan to the genus, much larger than the coracoid of T. hildegardae and almost as long as that of C. hexeris. It was then the first appearance of the genus Tonsala in Japan. In 2000, James L. Goedert and John Cornish referred to the type species two newly discovered specimens collected respectively in 1984 and 1986 in the lower part of the Pysht Formation, near the type locality of the holotype, and including two pelvis, fragmentary vertebral, forelimb and hindlimb remains, and portions of the dentary. In 2011, Gareth J. Dyke, Xia Wang and Michael B. Habib proposed a new species based on Oligocene fossils found in the Pysht Formation and the underlying Makah Formation, Tonsala buchanani. In 2015, three new specimens, including two additional cranial remains, of Tonsala hildegardae, collected respectively in 1985, 1989 and 2008 by James L. Goedert in Oligocene sediments from the Pysht Formation, were described by Gerald Mayr, Goedert and Olaf Vogel. In 2016, Mayr and Goedert referred two additional specimens from the Late Eocene to Early Oligocene of the Jansen Creek Member of the Makah Formation to the genus Tonsala, including one partial pelvis collected in 2004 by Goedert, tentatively assigned to T. hildegardae, and a right coracoid collected in 2009 by D. W. Starr tentatively referred to the genus as ?Tonsala sp., and suggested that T. buchanani represented more than one species and had been incorrectly attributed to the genus Tonsala. In 2017, Mayr and Goedert used Tonsala as the type genus of the new clade Tonsalinae, comprising all derived Plotopterids, aside from the primitive and fragmentary Phocavis and the small-sized Stemec and Plotopterum; they additionally referred to the genus, as a new specimen of T. hildegardae, a partial skeleton including most notably the first known tarsometatarsus assigned to the genus. In 2019, the Japanese remains assigned tentatively to a new species of Tonsala by Olson and Hasegawa in 1996 were redescribed and assigned to a new genus and species, Stenornis kanmonensis In 2021, T. buchanani was moved to the genus Klallamornis by Mayr and Goedert, as K. buchanani, becoming the new type species of the genus. Additional criticism of Dyke et al, 2016 led to a reevaluation of the specimens assigned to Tonsala; one of the partial skeletons referred to the type species by Dyke et al. was only tentatively referred by Mayr and Goedert, as cf. Tonsala hildegardae.
Etymology The genus name, Tonsala, is constructed with the Latin prefix "Tonsa-", meaning "oar", and the suffix "-ala", meaning wing, referencing the adaptation of its forelimbs as a swimming apparatus; the species name, hildegardae, was given to honour Hildegarde Howard, the American paleontologist who described Plotopterum.
Description
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