Dusignathus

Dusignathus; Temporal range: Miocene to Pliocene,
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Infraclass:	Placentalia
Order:	Carnivora
Parvorder:	Pinnipedia
Family:	Odobenidae
Genus:	†Dusignathus; Kellogg, 1927
Type species
	Dusignathus santacruzensis;
Species
	D. santacruzensis Kellogg, 1927 ; D. seftoni Deméré, 1994 ;

Dusignathus is an extinct genus of walrus belonging to the family Odobenidae.¹ The genus name means "jaw of the setting sun," a reference to its occurrence on the west coast of North America. Unlike the modern walrus, which bears tusks only on the upper jaw, Dusignathus possessed enlarged canine tusks on both the upper and lower jaws, a trait shared with its close relative Gomphotaria and characteristic of the subfamily Dusignathinae.²

Discovery and naming

The genus was first described by Remington Kellogg in 1927, based on fossil material from Santa Cruz California. The holotype of the type species, D. santacruzensis, consists of a fragmentary skull and a well-preserved pair of mandibles collected from a cliff near the wharf.³ The type locality was later clarified to the Purisima Formation by Mitchell (1962).⁴

A second species, D. seftoni, was named by Thomas Deméré in 1994 from specimens recovered during a paleontological mitigation project in southern California, including an immature skull, a large mandible, and several postcranial elements from the Pliocene San Diego Formation.⁵²

Fossil record

Fossils of Dusignathus have been found along the West Coast from California to Isla de Cedros in Mexico.⁶ D. santacruzensis is represented by eight collections and D. seftoni by three collections in the Paleobiology Database.⁶

References

Kellogg, R. (1927). "Fossil Pinnipeds from California". Contributions to Palaeontology. Carnegie Institution of Washington Publication. Vol. 346. Washington, D.C.: Carnegie Institution of Washington. pp. 25–37.
Boessenecker, Robert (September 2014). "The evolutionary history of walruses, part 3: double tusked walruses – the dusignathines". The Coastal Paleontologist.
Boessenecker, Robert (October 2009). "Reconstructing a fossil walrus, part 1: the enigmatic Dusignathus santacruzensis". The Coastal Paleontologist.
Mitchell, E.D. (1962). "A walrus and a sea lion from the Pliocene Purisima Formation at Santa Cruz, California: with remarks on the type locality and geologic age of the sea lion Dusignathus santacruzensis Kellogg". Los Angeles County Museum Contributions in Science. 56: 1–24.
Deméré, T.A. (1994). "Two new species of fossil walruses (Pinnipedia: Odobenidae) from the Upper Pliocene San Diego Formation, California". Proceedings of the San Diego Society of Natural History. 29: 77–98.
"PBDB Taxon". paleobiodb.org.

[1] Kellogg, R. (1927). "Fossil Pinnipeds from California". Contributions to Palaeontology. Carnegie Institution of Washington Publication. Vol. 346. Washington, D.C.: Carnegie Institution of Washington. pp. 25–37.

[coastalpaleo2014-2] Boessenecker, Robert (September 2014). "The evolutionary history of walruses, part 3: double tusked walruses – the dusignathines". The Coastal Paleontologist.

[coastalpaleo2009-3] Boessenecker, Robert (October 2009). "Reconstructing a fossil walrus, part 1: the enigmatic Dusignathus santacruzensis". The Coastal Paleontologist.

[4] Mitchell, E.D. (1962). "A walrus and a sea lion from the Pliocene Purisima Formation at Santa Cruz, California: with remarks on the type locality and geologic age of the sea lion Dusignathus santacruzensis Kellogg". Los Angeles County Museum Contributions in Science. 56: 1–24.

[demere1994a-5] Deméré, T.A. (1994). "Two new species of fossil walruses (Pinnipedia: Odobenidae) from the Upper Pliocene San Diego Formation, California". Proceedings of the San Diego Society of Natural History. 29: 77–98.

[pbdb-6] "PBDB Taxon". paleobiodb.org.

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