The firstEsox(Esocidae: Teleostei) from the Eocene Green River Formation, and a brief review of esocid fishes

Abstract

A new species of esocid, †Esox (Kenoza) kronneri sp. nov., is described from the early Eocene Fossil Butte Member of the Green River Formation, southwestern Wyoming. This is the first member of the order Esociformes reported from the Green River Formation. It is also the first articulated fossil esocid from North America identified as a pickerel (=subgenus Kenoza). The new species is known by only a single specimen. Consequently, it was probably not a normal resident of Fossil Lake, considering the hundreds of thousands of fishes that have been excavated from this locality over the last 140 years. Although small (118 millimeters long), the specimen is one of the best-preserved fossil esociforms ever reported. The new species appears to be closely related to the extant species †Esox americanus (which includes two extant subspecies, †E. americanus americanus and †E. americanus vermiculatus), but much work is yet needed to adequately resolve the interrelationships of living and well-preserved fossil Esocidae. Comparative osteology of even the extant species of Esocidae is still in need of rigorous comprehensive study. Esocidae have a rich fossil record, ranging from Late Cretaceous to Holocene and covering much of the northern hemisphere. Reported fossil esocids are listed here for future reference. Discovery of Esocidae in the Green River Formation adds yet another extant family to the already diverse faunal list. Besides representing the world's richest freshwater Lagerstätte, the Green River Formation provides an unparalleled look at the early development of the modern North American freshwater fish fauna. It is clear that the fossil fish fauna of the Green River Formation should be included as a critical component of any comprehensive study of the origin and affinities of the modern North American freshwater fish fauna.