Crown beaked whale fossils from the Chepotsunai Formation (latest Miocene) of Tomamae Town, Hokkaido, Japan

[摘要] In the last decades, our knowledge of ziphiid evolution has increased dramatically. However, their periotic morphology is still poorly known. A fossil ziphiid (TTM-1) including the periotic, bulla, isolated polydont teeth and vertebrae from the Chepotsunai Formation (latest Miocene) of Tomamae Town, Hokkaido, Japan, is identified as a member of a clade with crown ziphiids of Bianucci et al. (2016) by having three periotic synapomorphies; a posteriorly wide posterior process, transversely thick anterior process, and laterally elongated lateral process. The specimen adds morphological information of the periotic. Among the Ziphiidae from the stem to crown, the periotic morphologies were changed to having a more robust anterior process, wider anterior bullar facet and posterior process. The crown Ziphiidae shares a feature; enlarged medial tubercle on the anterior process. Among the crown Ziphiidae, TTM-1 does not have a swollen medial tubercle not likeTasmacetus, Nazcacetus and others. This new morphological information might represent useful future phylogenetic comparisons.

[学科分类] 地质学

[关键词] Yoshihiro Tanaka;Mahito Watanabe;Masaichi Kimura;Ziphiidae;Odontoceti;Messinian;Periotic;Petrosal