Hypsidoris farsonensis Lundberg & Case, 1970

Hypsidoris farsonensis Lundberg & Case, 1970

Eocene

Laney Shale Member

Big Sandy Reservoir

Farson

Wyoming

USA

Length 15 cm / 6"

a Green River Formation catfish

Astephus and Hypsidoris are both members of the Family Ictaluridae, native to North America. Green River catfish are easily recognized by their stout dorsal and pectoral spines, scale less bodies and broad skull. Ictalurid species have four pairs of barbels (or whiskers). Like modern catfish, they possessed a vibration sensitive organ called the Weberian apparatus. The Weberian apparatus consists out of specialized vertebrae at the front of the spinal column which passed vibrations to the inner ear using the swim bladder as a resonance chamber. The structure essentially acts as an amplifier of sound waves that would otherwise be only slightly perceivable by the inner ear structure alone.

Normal size of Astephus is around 15cm and rarely exceeds 18cm, maximum total length is about 30cm. Hypsidoris seems to be in the same size range.

The diet of Green River catfish was probably similar to existing ictalurids consisting of plants, small fish, crayfish and mollusks. Astephus and Hypsidoris were probably bottom feeders.

Astephus antiquus is unknown as a body fossil in the middle unit of Fossil Butte Member, and only one specimen has been found in all of Fossil Lake, although it is abundant in Lake Gosiute strata.

Hypsidoris farsonensis has only been found in Lake Gosiute deposits of the Green River Formation, east of Fossil Lake.

The discovery of numerous and widespread fossil catfish in oil shale units of the Laney Member of the Eocene Green River Formation is evidence of aerobic conditions in the hypolimnic waters of ancient Lake Gosiute.

Grande, L. and J. G. Lundberg. 1988. Revision and redescription of the genus Astephus (Siluriformes: Ictaluridae) with a discussion of its phylogenetic relationships. J. Vert. Paleont 8:139–171.

Grande, L. 1987. Redescription of Hypsidoris farsonensis (Teleostei: Siluriformes), with a reassessment of its phylogenetic relationships. Journal of Vertebrate Paleontology 7:24–54.

Grande, L. and M. C. C. de Pinna. 1998. Description of a second species of the catfish Hypsidoris and a reevaluation of the genus and the family Hypsidoridae. Journal of Vertebrate Paleontology 18:451–474.