Gol'din Pavel, Steeman Mette Elstrup
Department of Natural History and Palaeontology, The Museum of Southern Jutland, Lergravsvej 2, 6510, Gram, Denmark.
PLoS One. 2015 Sep 2;10(9):e0135500. doi: 10.1371/journal.pone.0135500. eCollection 2015.
Miocene baleen whales were highly diverse and included tens of genera. However, their taxonomy and phylogeny, as well as relationships with living whales, are still a subject of controversy. Here, "Mesocetus" argillarius, a poorly known specimen from Denmark, is redescribed with a focus on the cranial anatomy. It was found to represent not only a new genus, Tranatocetus gen. nov., but also a new family; Tranatocetidae. The whales of this family have the rostral bones either overriding or dividing the frontals; the rostral bones are contacting the parietals and nasals dividing the maxillae on the vertex; the occipital shield is dorsoventrally bent. The tympanic bulla is particularly characteristic of this family featuring a short, narrow anterior portion with a rounded or squared anterior end and a wider and higher posterior portion that is swollen in the posteroventral area. A phylogenetic analysis including 51 taxa supports a monophyletic group comprising most Neogene and modern whales, with Tranatocetidae being possibly closer related to Balaenopteridae (rorquals) than to Cetotheriidae. Tranatocetidae exhibit a charahteristic bulla shape. In fact, all Neogene and modern mysticete families examined have a unique shape of the tympanic bulla that is diagnostic at family-level. Inclusion of problematic taxa like Tranatocetus argillarius in phylogenies brings new understanding of the distribution and diagnostic value of character traits. This underlines the need for re-examination of earlier described specimens in the light of the wealth of new information published in later years.
中新世须鲸种类高度多样，包含数十个属。然而，它们的分类学、系统发育以及与现存鲸鱼的关系仍然存在争议。在此，对来自丹麦的一个鲜为人知的标本“Mesocetus” argillarius进行重新描述，重点关注其颅骨解剖结构。结果发现它不仅代表一个新属，即Tranatocetus属，还代表一个新科，即Tranatocetidae科。该科鲸鱼的吻骨要么覆盖要么分隔额骨；吻骨与顶骨和鼻骨接触，在头顶处将上颌骨分隔开；枕骨盾在背腹方向弯曲。鼓泡是该科特别典型的特征，其前部短而窄，前端呈圆形或方形，后部更宽更高，在腹后区域肿胀。一项包含51个分类单元的系统发育分析支持一个单系类群，该类群包括大多数新近纪和现代鲸鱼，Tranatocetidae科可能与须鲸科（须鲸）的关系比与灰鲸科更密切。Tranatocetidae科呈现出一种独特的鼓泡形状。事实上，所有被研究的新近纪和现代须鲸科都有独特的鼓泡形状，这在科级水平上具有诊断意义。在系统发育研究中纳入像Tranatocetus argillarius这样有问题的分类单元，能带来对特征性状分布和诊断价值的新认识。这凸显了根据近年来发布的大量新信息重新审视早期描述标本的必要性。
