Mysticeti () (from Latin ὁ μῦς τὸ κῆτος "the mouse, the whale so called" ), or baleen whales, are a widely distributed and diverse parvorder of carnivorous marine mammals. They comprise the families Balaenidae (right whales), Balaenopteridae (rorqual), Eschrichtiidae (the gray whale), and Cetotheriidae (the pygmy right whale). There are currently 15 species of baleen whale. While cetaceans were historically thought to have descended from mesonychids, molecular evidence supports them as relatives of even-toed ungulates (Artiodactyla). Baleen whale split from toothed whales (Odontoceti) around 34 million years ago.