A New Cetacean from the Late Eocene La Meseta Formation Seymour Island, Antarctic Peninsula

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Abstract
The new genus and species Llanocetus denticrenatus is described based on a cranial endocast and portion of a dentary fragment bearing two teeth from the Eocene La Meseta Formation, Seymour Island, Antarctic Penninsula. Llanocetus new genus is designated the type genus for the new family Llanocetidae. The Llanocetidae is placed within the new infraorder Crenaticeti, co-ordinate with the new Mysticete infraorder Chaeomysticeti. Llanocetus denticrenatus new species shows relationship with both Archaeoceti and Mysticeti. Revision of archaeocete and mysticete classification includes proposal of the new taxa Kekenodontinae, Mammalodontidae, and the new ranks Protocetoidea, Remingtonocetoidea, Basilosauroidea, and Eschrichtioidea. The endocast shows evidence of intracranial retial hypertrophy, taken as evidence of enhanced diving abilities. The large deeply notched teeth are widely spaced on the lower jaw. I hypothesize that filter feeding in whales arose first in species in which teeth with deep notches, forming widey spaced tubercles, comprised part of a straining apparatus analogous to the serrated teeth of the phocid seal Lobodon carcinophagus.