Morphology of the Petrosal in Late Miocene Baleen Whales of Northwestern Ciscaucasia

Abstract

Morphological features of the membranous labyrinth in extinct and extant baleen whales and their ancestors are discussed. The tomography of the membranous labyrinth of two species of Late Miocene baleen whales from Adygea has shown that Kurdalagonus, Zygiocetus, and Cetotherium have a comparable number of cochlear turns with representatives of herpetocetins, i.e., about three turns. Representatives of the genus Kurdalagonus differ from Zygiocetus in the structure of semicircular canals, the longer crus commune (much shorter in Zygiocetus), and in the size of the ampulla of the lateral semicircular canal. In addition, representatives of the genus Kurdalagonus differ from Zygiocetus and Cetotherium in the structure of the round window, which is much wider and has a more rounded shape.