Cranial ontogeny of Thamnophis radix (Serpentes: Colubroidea) with a re-evaluation of current paradigms of snake skull evolution

Accurate knowledge of skeletal ontogeny in extant organisms is crucial in understanding important morpho-functional systems and in enabling inferences of the ontogenetic stage of fossil specimens. However, detailed knowledge of skeletal ontogeny is lacking for most squamates, including snakes. Very few studies have discussed postnatal development in snakes, with none incorporating data from all three major ontogenetic stages – embryonic, juvenile, and adult. Here, we provide the first analysis encompassing these three ontogenetic stages for any squamate, using the first complete micro-computed tomography (micro-CT)-based segmentations of any non-adult snake, based on fresh specimens of Thamnophis radix. The most significant changes involve the feeding apparatus, with major elongation of the tooth-bearing elements and jaw suspensorium causing a posterior shift in the jaw articulation. This shift enables macrostomy (large-gaped feeding in snakes) and occurs in T. radix via a different dev...

准确掌握现生生物的骨骼个体发育（skeletal ontogeny）知识，对于解析关键形态功能系统、推断化石标本的个体发育阶段均具有核心意义。然而，包括蛇类在内的绝大多数有鳞目（squamates）动物的骨骼个体发育细节仍有待系统补充。目前针对蛇类出生后发育的研究寥寥无几，且尚无研究涵盖胚胎期、幼年期与成年期这三大核心个体发育阶段的完整数据。本研究以红边束带蛇（Thamnophis radix）的新鲜标本为材料，完成了首例非成年蛇类的完整显微计算机断层扫描（micro-computed tomography，micro-CT）分割重建，首次实现了针对有鳞目动物三大个体发育阶段的系统性分析。本次分析中最显著的形态变异集中于摄食器官：承载牙齿的骨骼结构与颌悬器发生显著伸长，致使颌关节向后移位。该移位为蛇类的大口摄食（macrostomy）提供了结构基础，且红边束带蛇的该发育过程采用了一种独特的发育机制……