Guo Zixuan, Kohno Naoki
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.
Department of Geology and Paleontology, National Museum of Nature and Science, Tsukuba, Japan.
PeerJ. 2021 Feb 24;9:e10945. doi: 10.7717/peerj.10945. eCollection 2021.
A new species of an extinct dolphin belonging to the kentriodontids, i.e., sp. nov., is described from the upper lower to lowest middle Miocene Kadonosawa Formation in Ninohe City, Iwate Prefecture, northern Japan. The holotype of sp. nov., consists of a partial skull with ear bones, mandibular fragments, and some postcranial bones. This new species shares five unique characters with other species of . In addition, the new species differs from other species of the genus in displaying a narrow width of the squamosal lateral to the exoccipital in posterior view, the dorsolateral edge of the opening of the ventral infraorbital foramen that is formed by the maxilla and the lacrimal or the jugal, and at least three anterior dorsal infraorbital foramina. Our phylogenetic analysis based on 393 characters for 103 Odontoceti taxa yielded a consensus tree showing all previously identified kentriodontids as a monophyletic group that comprises the sister group of the crown Dephinoidea, which in turn include Delphinidae, Phocoenidae and Monodontidae. Our analysis also indicates that the distinct innovation of the acoustic apparatus (i.e., 13 out of 29 derived characters are from tympanoperiotic) would have occurred in the ancestral lineage of the Delphinoidea (sensu lato) including the monophyletic Kentriodontidae during their initial evolution and diversification.
一种属于肯氏海豚科的已灭绝海豚新物种（即新种），是从日本北部岩手县二户市中新世下上部至中下部的鹿之泽组中描述出来的。该新种的正模标本包括一个带有听骨的部分头骨、下颌骨碎片和一些颅后骨骼。这个新物种与该科的其他物种共有五个独特特征。此外，这个新物种与该属的其他物种不同之处在于，从后视图看，枕骨外侧的颞骨宽度较窄，由上颌骨和泪骨或颧骨形成的腹侧眶下孔开口的背外侧边缘，以及至少三个前背眶下孔。我们基于103个齿鲸类分类单元的393个特征进行的系统发育分析得出了一个共识树，显示所有先前确定的肯氏海豚科为一个单系群，它构成了冠海豚总科姐妹群，而冠海豚总科又包括海豚科、鼠海豚科和独角鲸科。我们的分析还表明，听觉器官的独特创新（即29个衍生特征中有13个来自鼓室听骨）可能发生在包括单系肯氏海豚科在内的广义海豚总科的祖先谱系在其最初进化和多样化过程中。
