Whole feeding apparatus 3D landmarks

The kinetic skull is a key innovation that allowed snakes to capture,
manipulate, and swallow prey exclusively using their heads using the
coordinated movement of 8 bones. Despite these unique feeding behaviors,
patterns of evolutionary integration and modularity within the feeding
bones of snakes in a phylogenetic framework have yet to be addressed.
Here, we use a dataset of 60 µCT scanned skulls and high-density geometric
morphometric methods to address the origin and patterns of variation and
integration in the feeding bones of aquatic-foraging snakes. By comparing
alternate superimposition protocols allowing us to analyze the entire
kinetic feeding system simultaneously, we find that the feeding bones are
highly integrated, driven predominantly by functional selective pressures.
The most supported pattern of modularity contains four modules, each
associated with distinct functional roles: the mandible, the
palatopterygoid arch, the maxilla, and the suspensorium. Further, the
morphological disparity of each bone is not linked to its magnitude of
integration, indicating that integration within the feeding system does
not strongly constrain morphological evolution, and that adequate
biomechanical solutions to a wide range of feeding ecologies and behaviors
are readily evolvable within the constraint due to integration in the
snake feeding system.

可动颅骨（kinetic skull）是蛇类一项关键的演化创新，使其仅依靠头部与8块骨骼的协同运动，即可完成捕获、操控并吞咽猎物的全过程。尽管蛇类具备这类独特的摄食行为，但在系统发育框架下，其摄食骨骼的演化整合与模块化模式仍有待研究。本研究依托60例经显微CT（µCT）扫描的颅骨标本数据集，结合高密度几何形态测量学（geometric morphometric）方法，探讨水生觅食蛇类摄食骨骼的起源、变异模式与整合规律。通过对比不同的叠加配准方案，我们得以同时分析完整的可动摄食系统，结果显示摄食骨骼整体呈现高度整合性，该特征主要受功能选择压力驱动。支持度最高的模块化模式包含4个模块，分别对应独特的功能角色：下颌骨、腭翼骨弓、上颌骨与悬器。进一步分析发现，每块骨骼的形态差异度与其整合程度并无关联，这表明摄食系统内的整合并未对形态演化形成强约束；同时，在蛇类摄食系统的整合约束范围内，适配各类摄食生态与行为的完备生物力学解决方案，均可通过演化轻易获得。