Alternative combinations: Cetotherium expansus, Eschrichtius expansus, Megaptera expansa
Full reference: E. D. Cope. 1868. Second contribution to the history of the Vertebrata of the Miocene period of the United States. Proceedings of the Academy of Natural Sciences of Philadelphia 1868:184-194
Belongs to Siphonocetus according to E. D. Cope 1895
Sister taxa: Aetiocetidae, Aetiocetoidea, Balaenoptera cortesii portisii, Cetotherioidea, Cetotheriopsis, Chaeomysticeti, Eomysticetidae, Llanocetidae, Mammalodontidae, Mauicetus, Physalidae, Pterobalaenidae
Type specimen: ANSP 12769, a set of vertebrae. Its type locality is James T. Thomas estate, which is in a Langhian marine horizon in the Calvert Formation of Maryland.
Ecology: aquatic carnivore-suspension feeder