Türtscher Julia, López-Romero Faviel A, Jambura Patrick L, Kindlimann René, Ward David J, Kriwet Jürgen
Department of Palaeontology, University of Vienna, Althanstraβe 14, 1090 Vienna, Austria.
Haimuseum und Sammlung R. Kindlimann, Aathal-Seegräben, Switzerland.
Paleobiology. 2021 Nov;47(4):574-590. doi: 10.1017/pab.2021.6. Epub 2021 Mar 24.
Sharks have a long and rich fossil record that consists predominantly of isolated teeth due to the poorly mineralized cartilaginous skeleton. Tiger sharks (), which represent apex predators in modern oceans, have a known fossil record extending back into the early Eocene (ca. 56 Ma) and comprise 22 recognized extinct and one extant species to date. However, many of the fossil species remain dubious, resulting in a still unresolved evolutionary history of the tiger shark genus. Here, we present a revision of the fossil record of by examining the morphological diversity and disparity of teeth in deep time. We use landmark-based geometric morphometrics to quantify tooth shapes and qualitative morphological characters for species discrimination. Employing this combined approach on fossil and extant tiger shark teeth, our results only support six species to represent valid taxa. Furthermore, the disparity analysis revealed that diversity and disparity are not implicitly correlated and that retained a relatively high dental disparity since the Miocene despite its decrease from four to one species. With this study, we demonstrate that the combined approach of quantitative geometric morphometric techniques and qualitative morphological comparisons on isolated shark teeth provides a useful tool to distinguish between species with highly similar tooth morphologies.
鲨鱼有着悠久而丰富的化石记录，由于其软骨骨骼矿化程度低，化石记录主要由孤立的牙齿组成。虎鲨是现代海洋中的顶级掠食者，其已知化石记录可追溯到始新世早期（约5600万年前），迄今为止包括22个已确认的灭绝物种和1个现存物种。然而，许多化石物种仍存在疑问，导致虎鲨属的进化史仍未解决。在这里，我们通过研究深海时期牙齿的形态多样性和差异，对虎鲨的化石记录进行了修订。我们使用基于地标点的几何形态测量学来量化牙齿形状，并使用定性形态特征进行物种鉴别。将这种综合方法应用于化石和现存虎鲨牙齿上，我们的结果仅支持六个物种代表有效分类单元。此外，差异分析表明，多样性和差异并非必然相关，并且自中新世以来，虎鲨的牙齿差异相对较高，尽管其物种数量从四个减少到了一个。通过这项研究，我们证明了对孤立鲨鱼牙齿进行定量几何形态测量技术和定性形态比较的综合方法，为区分牙齿形态高度相似的物种提供了一个有用的工具。
