Data from: A systematic review of cetothere baleen whales (Cetacea, Cetotheriidae) from the Late Miocene of Crimea and Caucasus, with a new genus

Nine taxa of Miocene baleen whales were described from the Black Sea
region under the name Cetotherium before 1951, and a further four closely
related species representing three genera have been added in recent years.
This rich diversity requires taxonomic revision and ordering. Here, a new
genus, Mithridatocetus, is described from the Tortonian of Crimea and
Caucasus, with two species, M. eichwaldi and M. adygeicus (originally
Kurdalagonus adygeicus); ‘Cetotherium’ mayeri (a nomen dubium) is also a
member of this genus. In comparison with other Cetotheriinae,
Mithridatocetus is distinguished by the autapomorphic shape of the
tympanic bulla with the swollen main ridge, the lowered anterior portion
of the involucrum and the oblique anterolateral margin; such
synapomorphies, as a transversely narrow squamosal with the ventromedially
oriented postglenoid process (shared with Eucetotherium), a squamosal
cleft (shared with Kurdalagonus) and an oval surface of the compound
posterior process of the tympanoperiotic on the posterolateral skull wall
(shared with Brandtocetus); and a unique combination of a high
neurocranium and a long and robust paroccipital process. The genus
Kurdalagonus is redefined here as containing only one described species,
K. mchedlidzei. Therefore, the group Cetotheriinae is now restricted to
the latest Serravallian and Tortonian of the Eastern Paratethys and
includes at least five genera: Cetotherium, Brandtocetus, Kurdalagonus,
Mithridatocetus and Zygiocetus. In addition, ?Cetotherium priscum and C.
incertum are considered to be nomina dubia; ‘Cetotherium’ klinderi and
‘Cetotherium’ pusillum require more complete specimens for reassessment;
‘Cetotherium’ maicopicum and Eucetotherium helmersenii require further
research to identify their taxonomical affinities.