Llanocetus

Llanocetus ( "Llano's whale" ) is a genus of extinct toothed baleen whales from the Late Eocene of Antarctica and New Zealand. The type species, Llanocetus denticrenatus, reached gigantic proportions, with the juvenile specimen reaching an estimated in length; a second, unnamed species, known only from three isolated premolar teeth, reached an estimated total body length of up to . Like other contemporary baleen whales of the Eocene, Llanocetus completely lacked baleen in its jaws. It was probably a suction feeder like the modern beaked and pygmy right whales.

==History== Llanocetus was described in 1989 by paleontologist Edward Mitchell based on a partial mandible with two teeth, specimen USNM 183022, and an endocast of the braincase, referred to the same specimen, from the La Meseta Formation of Seymour Island, Antarctica. They were excavated in 1974–75 by a joint team from the Instituto Antártico Argentino, Ohio State University and Northern Illinois University. The complete skull belonging to the holotype specimen was described in 2018 by paleontologists Robert Ewan Fordyce and Felix Marx. It was excavated in the 1980s, with the assistance of Fordyce, and shipped to New Zealand for preparation and study. In 2023 the skull will be transferred to the Smithsonian, reuniting the holotype material. Though Mitchell, based on the size and density of the bone, thought the specimen was an adult, Fordyce and Marx concluded it was a juvenile due to the loss of both epiphyses—which are the surfaces that the vertebra connects to the other vertebrae to—on the single preserved neck vertebra.