Two new extinct basal phocoenids (Cetacea, Odontoceti, Delphinoidea), from the upper Miocene Koetoi Formation of Japan and their phylogenetic significance

Mizuki Murakami, Chieko Shimada, Yoshinori Hikida, Hiromichi Hirano

    Research output: Contribution to journalArticle

    28 Citations (Scopus)

    Abstract

    Two new extinct porpoisesArchaeophocaena teshioensis, gen. et sp. nov., and Miophocaena nishinoi, gen. et sp. nov.are described from the upper Miocene Koetoi Formation (5.5-6.4 Ma) of Hokkaido, Northern Japan. The holotype of the former is composed of a partial skull, whereas the holotype of the latter is composed of a partial skull, right periotic, right stylohyoid, and pelvis. Both species are assigned to Phocoenidae on the basis of a unique combination of phocoenid characters: presences of frontal bosses, nasal protuberances, premaxillary eminences, and fossae for the inferior vestibule. However, they do not have dorsally developed preorbital sinus fossae or high premaxillary eminences, unlike derived phocoenids. Furthermore, their premaxillae contact the nasals (or the right premaxilla alone contacts the right nasal), unlike all other known phocoenids except Pterophocaena. A comprehensive morphological cladistic analysis indicates that the two new extinct species are the second-most basal phocoenids next to Pterophocaena and that Phocoenidae is the sister group of Delphinidae. The cranial morphology of the two new extinct species is intermediate in form between that of phocoenids and delphinids, supporting the hypothesis of a sister relationship for the two groups. Thus, these new species fill not only the morphological gap between Phocoenidae and other families of Delphinoidea but also a temporal gap in the fossil record of phocoenids in the western North Pacific.

    Original languageEnglish
    Pages (from-to)1172-1185
    Number of pages14
    JournalJournal of Vertebrate Paleontology
    Volume32
    Issue number5
    DOIs
    Publication statusPublished - 2012 Sep 1

    ASJC Scopus subject areas

    • Palaeontology

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