REVIEW OF THE FOSSIL RECORD OF STURGEONS, FAMILY ACIPENSERIDAE (ACTINOPTERYGII: ACIPENSERIFORMES), FROM NORTH AMERICA

Abstract

The pre-Pleistocene fossil record of sturgeons (family Acipenseridae) from North America is reviewed based on a survey of reports in the literature and firsthand examination of specimens in museum collections. We provide a redescription of the only known specimen of † Protoscaphirhynchus squamosus(Late Cretaceous, Montana), a very poorly preserved specimen for which few morpho- logical details can be determined. Three taxa described as species of the genus Acipenser from North America († A. albertensis ,† A. eruciferus, and † A. ornatus) were described based on isolated and fragmentary remains, and are here considered to be nomina dubia. The earliest reported remains of North American sturgeons are from the Late Cretaceous (Santonian to Campanian Milk River For- mation). There is a relatively continuous record, with the exception of the Eocene and Oligocene, in which there are few (potentially in the Eocene) or no (Oligocene) known specimens available in collections. We have found that nearly all specimens are best regarded as Acipenseridae indeterminate genus and species due to their fragmentary preservation and lack of preserved diagnostic characters.