Redescription of Hypsidoris farsonensis (Teleostei: Siluriformes), with a reassessment of its phylogenetic relationships

ABSTRACT

†Hypsidoris farsonensis Lundberg and Case (1970) from the Eocene Green River Formation of Wyoming, is redescribed in detail based on much new material. The new material consists of (1) better preparations of the original type and referred specimens, and (2) many previously unreported specimens with exceptionally detailed preservation. Based on new information presented here †H. farsonensis is interpreted (A) not to belong in Ictaluridae as originally proposed, and (B) to be the sister group to all known catfish families other than Diplomystidae. Diplomystidae appears to be the sister group to †Hypsidoris plus all other known catfishes. Because of its apparent phylogenetic position (sister group to a group containing thirty nominal families), †Hypsidoris is given superfamilial (†Hypsidoroidea, new superfamily) and familial (†Hypsidoridae, new family) rank, and may be more relevant to our understanding of the early evolution of siluriform subgroups than previously thought.

Catfishes (Siluriformes) are a major group of freshwater fishes with 32 nominal families and over 2200 species, but so far relatively little is known about the higher (e.g. interfamilial) relationships of the group. †Hypsidoris could potentially play a major role in deciphering the phylogenetic relationships of siluroids by providing a second basal outgroup (in addition to Diplomystidae) within Siluriformes.