A New Species of Baleen Whale (Isanacetus-Group) from the Early Miocene, Japan
A New Species of Baleen Whale (Isanacetus-Group) from the Early Miocene, Japan
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DOI：
10.2517/pr210009
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发表时间：
2022-10
影响因子：
0.9
通讯作者：
T. Kimura;Y. Hasegawa;Tadashi Suzuki
中科院分区：
文献类型：
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作者：
T. Kimura;Y. Hasegawa;Tadashi Suzuki
摘要。isanacetus类群是鲸类中最神秘的类群之一。尽管它们的系统发育仍有争议，但许多先前的研究表明，它们是须鲸的一个副类群，包括须鲸科和须鲸科的祖先。在日本福岛县岩城的南岛多组（早中新世晚期，burdigian）发现了一具Isanacetus-group须鲸化石。标本由头盖骨、下颌骨和颅后部分组成，包括颈椎、胸椎、腰椎、肩胛骨、尺骨和肋骨。我们描述并诊断该标本为新属和新种，太平洋Jobancetus pacificus。该标本具有独特的形态特征组合，如前额在顶点形成一个三角形的凸起平台，前额眶上突上有锋利而发育良好的横嵴，前额和顶骨形成的矢状嵴，以及大的鳞状窝，其向后延伸远远超过枕髁后表面的水平。等权重下的系统发育分析表明，太平洋J. pacificus是Pligogulae的一个茎类，而隐含权重下的系统发育分析表明，太平洋J. pacificus是Balaenopteridae + Eschrichtiidae的一个茎类。J. pacificus的发现扩大了我们对神秘的isanacetus类群的了解。
Abstract. The Isanacetus-group is one of the most enigmatic groups of cetaceans. Although their phylogeny is still controversial, many previous studies suggested that they are a paraphyletic group of baleen whales, including an ancestor of Balaenopteridae and Eschrichtiidae. A new fossil from an Isanacetus-group baleen whale has been recovered from the Minamishirado Formation (latest early Miocene, Burdigalian), Iwaki, Fukushima Prefecture, Japan. The specimen consists of a cranium, mandible, and postcranial elements, including cervical, thoracic, and lumbar vertebrae, scapula, ulna, and ribs. We describe and diagnose the specimen as a new genus and species, Jobancetus pacificus. A unique combination of morphological characters characterized the specimen, e.g. frontals forming a triangular elevated plateau at the vertex, sharp, and well-developed transverse crest on the supraorbital process of frontal, sagittal crest formed by frontals and parietals, and large squamosal fossa, which is posteriorly extended well beyond the level of the posterior surface of the occipital condyle. Phylogenetic analysis under equal weighting suggests that J. pacificus is a stem group of Pligogulae, whereas the phylogenetic analyses under implied weightings suggest that J. pacificus is a stem group of Balaenopteridae + Eschrichtiidae. The discovery of J. pacificus expands our knowledge of the enigmatic Isanacetus-group.