Description of a second species of the catfish †Hypsidorisand a reevaluation of the genus and the family †Hypsidoridae

A second species of the genus †Hypsidoris is described from the primitive catfish family †Hypsidoridae. The new species is from Eocene freshwater deposits of the Clamo Formation of central Oregon and is known by numerous well-preserved skeletons. Like the type species from the Green River Formation of Wyoming, the Oregon species has a well-developed toothed maxilla, a feature thought to be primitive among catfishes. Among the more than 35 nominal families containing over 2,200 species of catfishes, only Diplomystidae and †Hypsidoridae have well-developed toothed maxillae. The relationships of †Hypsidoridae to other catfishes are briefly reviewed. The associated ichthyofauna is also briefly discussed in context with other Eocene faunas of western North America.