New Paleocene genus and species of smelt (Teleostei: Osmeridae) from freshwater deposits of the Paskapoo Formation, Alberta, Canada, and comments on osmerid phylogeny

Abstract

Articulated specimens of fish recovered from the Paskapoo Formation, of Tiffanian (Paleocene) age, near Red Deer, Alberta, are described as a new genus and species of smelt (Family Osmeridae). The new smelt is characterized by a long, toothed mandible and premaxilla and a slender, toothless maxilla, in combination with the virtual absence of teeth inside the mouth and a distinct second ural centrum. Cladistic analysis of osteological features of osmerids and several outgroups indicates that the new genus is most closely related to Plecoglossus, a Recent genus not always included in the family. These two in turn are more closely related to a derived clade of osmerid genera (Allosmerus, Osmerus, Spirinchus, Thaleichthys) than they are to primitive osmerids (Hypomesus and Mallotus). Anal fins of the new fish are sexually dimorphic, and several presumed males probably have breeding tubercles. Possibly the fish became stranded after attempting to spawn during a high-water stage. Anadromous life histories, which characterize many modern smelt species, may well have originated prior to the Paleocene. The Joffre Bridge fossil site, however, is so distant from Paleocene seas that it is unlikely that these particular fish were anadromous.