Cetotherium Brandt, 1843

Gol’Din, Pavel, Startsev, Dmitry & Krakhmalnaya, Tatiana, 2014, The anatomy of the Late Miocene baleen whale Cetotherium riabinini from Ukraine, Acta Palaeontologica Polonica 59 (4), pp. 795-814 : 797-798

Genus Cetotherium Brandt, 1843

Type species: Cetotherium rathkii Brandt, 1843 ; south coast of Taman Peninsula ; Tortonian , Late Miocene of the Eastern Paratethys .

Included species: Type species and Cetotherium riabinini Hofstein, 1948 .

Diagnosis ( Fig. 3 ).—Small cetotheres (3 to 4 m long; condylobasal length of skull ~ 1 m) differing from other members of the family in having a narrow rostrum, a roughly triangular (pointing dorsally) exposure of the posterior process of the tympanoperiotic on the posterolateral wall of the skull, a triangular occipital shield with a low and transversely wide external occipital crest, and a tympanic bulla as high and wide anteriorly as it is posteriorly; Cetotherium differs from all cetotheres except Kurdalagonus in having an anteroposteriorly short and dorsoventrally high zygomatic process of the squamosal and a transversely wide postglenoid process; differs from all cetotheres except “ Cetotherium ” mayeri sensu Riabinin 1934) in having a mandible with a straight, as opposed to laterally curved, distal portion; differs from Herpetocetus and Nannocetus in having a robust, bulbous paroccipital process; differs from Herpetocetus , Metopocetus , and Nannocetus in having a ventrally open (as opposed to partially floored) facial sulcus on the posterior process of the periotic; differs from all cetotheriids except Eucetotherium helmersenii ( Brandt, 1871) , Herpetocetus , and Nannocetus in having the postglenoid process oriented ventrally to ventromedially in posterior view; differs from Herpetocetus , Joumocetus , Metopocetus , Nannocetus , and Piscobalaena in having the proximal portion of the premaxilla not covered by the maxilla, and ascending processes of the maxillae approximating each other posteriorly without ever making contact.

Remarks.— Cetotherium has in the past been used as a wastebasket taxon for several species not belonging to this genus. In particular, the diagnoses of Brandt (1873), Spassky

1954), and Mchedlidze (1970) define a wider group including all cetotheriids.

Geographic and stratigraphic range.—Black Sea region; Tortonian, Late Miocene of the Eastern Paratethys.

Figures

Fig. 3. Comparison of the distal surface of the composite posterior process of the tympanoperiotic in posterolateral view in two cetotheriid baleen whales. A. Cetotherium riabinini Hofstein, 1948, Late Miocene of Nikolaev, Ukraine, NMNH-P 668/1. Photograph (A1), explanatory drawing (A2). B. Cetotherium rathkii Brandt, 1843, south coast of Taman Peninsula, Tortonian, Late Miocene, PIN 1840/1; inverted.