Aetiocetus cotylalveus (Emlong 1966; Oligocene, 30 mya) was originally and is traditionally considered a mysticete whale, basal to baleen whales like Balaenoptera. Here it nests with odontocete whales between Zygorhiza and Orcinus. Desmostylians, like Paleoparadoxia, nest closer to the origin of baleen whales.
Considered remarkable for the retention of nutrient foramnina (blood vessel channels in the palatal portion of the maxilla that indicate the presence of baleen tissues) |