Evers Serjoscha W, Ponstein Jasper, Jansen Maren A, Gray Jaimi A, Fröbisch Jörg
Department of Geosciences, University of Fribourg, Fribourg, Switzerland.
Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany.
Anat Rec (Hoboken). 2023 Jun;306(6):1228-1303. doi: 10.1002/ar.25037. Epub 2022 Jul 28.
Turtles are a charismatic reptile group with a peculiar body plan, which most notably includes the shell. Anatomists have often focused descriptive efforts on the shell and other strongly derived body parts, such as the akinetic skull, or the cervical vertebrae. Other parts of turtle osteology, like the girdles, limbs, and mandibles, are documented with less rigor and detail. The mandible is the primary skeletal element involved in food acquisition and initial food processing of turtles, and its features are thus likely linked to feeding ecology. In addition, the mandible of turtles is composed of up to seven bones (sometimes fused to as little as three) and has thus anatomical complexity that may be insightful for systematic purposes and phylogenetic research. Despite apparent complexity and diversity to the mandible of turtles, this anatomical system has not been systematically studied, not even in search of characters that might improve phylogenetic resolution. Here, we describe the mandibular osteology for all major subclades of extant turtles with the help of digitally dissected 3D models derived from high-resolution computed tomography (μCT) scans of 70 extant species. We provide 31 fully segmented mandibles, as well as 3D models of the mandibular musculature, innervation, and arterial circulation of the cryptodire Dermatemys mawii. We synthesize observed variation into 51 morphological characters, which we optimize onto a molecular phylogeny. This analysis shows some mandibular characters to have high systematic value, whereas others are highly homoplastic and may underlie ecological influences or other factors invoking variation.
龟是一类具有魅力的爬行动物，拥有独特的身体结构，其中最显著的就是龟壳。解剖学家常常将描述重点放在龟壳以及其他高度特化的身体部位，比如不能活动的头骨或颈椎上。龟类骨骼学的其他部分，如肩带、四肢和下颌骨，其记录的严谨性和细节程度则较低。下颌骨是龟获取食物和初步处理食物时涉及的主要骨骼元素，因此其特征可能与摄食生态相关。此外，龟的下颌骨由多达七块骨头组成（有时融合后只有三块），因而具有解剖学上的复杂性，这对于系统分类目的和系统发育研究可能具有启发意义。尽管龟的下颌骨明显具有复杂性和多样性，但这个解剖系统尚未得到系统研究，甚至都没有去寻找可能有助于提高系统发育分辨率的特征。在这里，我们借助从70个现存物种的高分辨率计算机断层扫描（μCT）扫描中获取的数字解剖3D模型，描述了现存龟所有主要亚类的下颌骨骨骼学。我们提供了31个完全分割的下颌骨，以及隐颈龟科的马格达莱纳侧颈龟下颌肌肉组织、神经支配和动脉循环的3D模型。我们将观察到的变异综合为51个形态特征，并将其优化到一个分子系统发育树上。该分析表明，一些下颌骨特征具有很高的系统分类价值，而其他一些特征则具有高度的同塑性，可能是生态影响或其他导致变异的因素的基础。
