Abstract
BackgroundFamily Cetotheriidae sensu stricto and several closely related taxa comprise the Cetotherioidea and represent a lineage of Neogene baleen whales that includes the smallest edentulous baleen whales in Earth history. Most of known cetotheriids came from the Late Miocene to Quaternary, and the earliest records from the latest Middle Miocene. The Paratethys region shows a great diversity of Middle to Late Miocene cetotheriids. That includes nominative taxon of the family, Cetotherium rathkii, and this suggests that the earliest cetotheriids may have lived in that region.Materials and methodsHere, Ciuciulea davidi, a new genus and species from the Middle Miocene of southeastern Europe, is described as the chronologically earliest and earliest diverging member of Cetotheriidae. Also, a new specimen of Otradnocetus, a basal Cetotherioidea sensu Gol’din & Steeman, 2015 is identified from the Late Miocene deposits of Caucasus and compared with Otradnocetus virodovi from the Middle Miocene of the same region.Results and discussionCiuciulea davidi is a dwarf whale displaying primitive traits: posterior ends of facial bones forming a single transverse line, a narrow occipital shield, and a relatively long interparietal region. Meanwhile, it shares some cetotheriid apomorphies: posteriorly telescoped wedge-shaped facial bones and an ovoid tympanic bulla with shallow lateral and medial furrows, a short anterior lobe and a short sigmoid process. Phylogenetic analysis suggests that Parietobalaena and Otradnocetus are branches diverging before the clade Cetotheriidae + Neobalaenidae. This is confirmed by the stepwise evolution of the anatomy of the squamosal, mandible, and ear bones across these groups. The re-described juvenile specimen of Otradnocetus differs from O. virodovi in the more primitive anatomy of the mandible and the autapomorphic anatomy of the humerus. Records of the earliest cetotheriids and related taxa in the Paratethys support the idea that this could be the region where Cetotheriidae evolved before their worldwide dispersal and radiation.
Highlights
The taxonomy and phylogeny of baleen whales of the family Cetotheriidae sensu stricto, along with that of other Neogene whales, was revised during the recent yearsHow to cite this article Gol’din (2018), New Paratethyan dwarf baleen whales mark the origin of cetotheres
Geological setting The specimen ZIRM V28/1 was collected in 1965 near the village Ciuciulea in the Republic of Moldova (Fig. 1) by Anatolie David. It was recovered from the late Badenian outcrops of the Fore-Carpathian Basin of the Paratethys (= early Serravallian, between 13.82 and 12.82 or 12.65 Ma), Middle Miocene
Ciuciulea differs from the other Middle Miocene mysticetes in an apomorphic shape of the bulla which is among the best diagnostic traits for baleen whales at the family level (Gol’din & Steeman, 2015): as in the other cetotheriids, the bulla has a short and thick sigmoid process, which is not distinctly swollen at the base, a low conical process, a moderately sized anterior lobe, a shallow sigmoid fissure and a shallow lateral furrow (Gol’din, Startsev & Krakhmalnaya, 2014)
Summary
The taxonomy and phylogeny of baleen whales of the family Cetotheriidae sensu stricto, along with that of other Neogene whales, was revised during the recent yearsHow to cite this article Gol’din (2018), New Paratethyan dwarf baleen whales mark the origin of cetotheres. From the Santa Margarita Fm. of California (12–10 Ma, Boessenecker, 2011) and Zygiocetus nartorum from the Krasnooktyabrskaya Fm., early Bessarabian (= late Serravallian, 12.1–11.6 Ma) of Maikop in Adygea, east to the Black Sea (Tarasenko, 2014) Another relevant specimen was identified as Cetotherium aff. The region of Paratethys where the latter two come from shows a great diversity of cetotheriids, based on reported findings (Gol’din & Startsev, 2017) starting with the nominative taxon of the family, Cetotherium rathkii (Brandt, 1843). This suggests that the earliest cetotheriids may have lived in that region. Records of the earliest cetotheriids and related taxa in the Paratethys support the idea that this could be the region where Cetotheriidae evolved before their worldwide dispersal and radiation
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