Data from: Evolutionary novelties and losses in geometric morphometrics: a practical approach through hominin molar morphology

Geometric morphometric techniques may offer a promising methodological approach to analyse evolutionary novelties in a quantitative framework. Nevertheless, and despite continuous improvements to this methodology, the inclusion of novel features in these studies presents some difficulties. In the present study, different methods to explicitly include novel traits in geometric morphometric analyses are compared, including homology-free approaches, landmark-based approaches, and combinations of both techniques. The 2D occlusal morphology of the lower second molar in multiple hominin species was chosen to evaluate these methods, as an example of an anatomical structure including one novelty: a distal fifth cusp is present in earlier hominins, and notably absent in many later Homo species. Results reveal that different approaches provide different results, highlighting that the design of the conformations of landmarks has a high impact on the inferred conclusions. Among diverse methods, a combined approach including landmarks, sliding semilandmarks, and only one landmark related to the studied novelty, was able to directly discern structures with and without the novel feature, circumventing some of the methodological difficulties associated with these traits. This study demonstrates the ability of geometric morphometric techniques to investigate evolutionary novelties and explores the implications of different methods, providing a reference context for future studies.

几何形态测量技术（Geometric morphometric techniques）可为在量化框架下分析演化新特征提供颇具前景的方法论路径。尽管该方法持续迭代优化，但在相关研究中纳入新特征仍存在若干难点。本研究对在几何形态测量分析中显性纳入新性状的多种方法展开对比，涵盖无同源性方法、基于解剖标志点（landmark）的方法以及两类技术的组合方案。本研究选取多个人亚族（hominin）物种的下颌第二磨牙二维咬合形态作为评估上述方法的示例对象——该解剖结构存在一项演化新特征：早期人亚族物种具有远中第五牙尖，而多数后期人属（Homo）物种则无此结构。研究结果显示不同方法会得到相异的结论，这凸显了解剖标志点构型的设计对推导所得结论具有显著影响。在多种方法中，融合解剖标志点、滑动半地标（semilandmarks）以及仅1个对应研究新特征的标志点的组合方案，能够直接区分存在与不存在该新特征的解剖结构，从而规避与这类性状相关的部分方法学难点。本研究证实了几何形态测量技术可用于探究演化新特征，并探讨了不同方法的应用意义，为后续相关研究提供了参考框架。