First record of the Eocene baleen whale Llanocetus outside Antarctica

Baleen whales (mysticetes) diverged from toothed whales and dolphins around 36 Ma. Among the oldest fossils attesting to their origin is Llanocetus denticrenatus from the Eocene (ca. 34 Ma) of Seymour Island, Antarctica. Isolated teeth from the same area suggest the presence of a second, potentially much larger species, but no further material of either form has been found to date. Here, we report the first record of Llanocetus outside Antarctica, based on a fragmentary but highly diagnostic tooth from Chatham Island, New Zealand. The new find considerably broadens both the geographical and the latitudinal range of the genus and suggests caution in interpreting the interrelationships of the basalmost mysticetes.