| Named By: | Edward D. Mitchell in 1989 |
| Time Period: | Priabonian |
| Location: | Antarctica, Seymour Island - Meseta Formation |
| Size: | Skull estimated at 2 meters long. Body length roughly estimated to be about 9 meters long |
| Diet: | Carnivore/filter feeder |
| Fossil(s): | Initially described by a partial skull, at least one more specimen has been recovered |
| Classification: | | Chordata | Mammalia | Cetacea | Mysticeti | |
Llanocetus ("Llano's whale") is a genus of extinct baleen whales from the Priabonian (Late Eocene) of Antarctica. Its fossilized remains were discovered on Seymour Island in the Antarctic Peninsula, within La Meseta Formation.
The remains -- a partial skull -- were described in 1989 by Edward D. Mitchell, who argued they belonged to a medium-sized whale which shared traits of both archaeocetes and mysticetes: it carried a wide, flat, and dorsoventrally flat rostrum, its jaw had heterodont teeth separated by wide diastemata, and the cheek teeth were two-rooted and palmated with accessory denticles. Additionally, fine grooves around the alveoli indicate the palate had a rich blood supply.
Mitchell interpreted Llanocetus as a basal mysticete with filter feeding behaviour, probably feeding on euphausiids or similar small animals. The sediments within which the fossil was found seems to indicate a lagoonar environment.
Mitchell created for the specimen the new monotypic family Llanocetidae, as well as the new monotypic genus Llanocetus and the species L. denticrenatus. The three new taxa were dedicated to the American biologist George A. Llano.