美国芝加哥大学ucja Fostowicz-Frelik团队研究团队发现，白垩纪晚期真兽亚纲动物重褶齿猬揭示，哺乳动物颈部独特的轴线和复杂的演化过程。2024年4月16日，《科学通报》杂志在线发表了这项成果。

研究人员表示，典型的哺乳动物颈部由七块颈椎骨（C1-C7）组成，这是在二叠纪晚期现代哺乳动物的犬齿龙先驱上形成的。这种结构精确地适应了进食、运动、躲避捕食者和社会交往时头部的运动。包括冠状胎生动物在内的真兽亚纲的化石记录可追溯到1.25亿年前，揭示了中生代显著的形态多样化。然而，人们对真兽亚纲颈椎形态的早期演化及其功能适应性知之甚少。

一个来自蒙古晚白垩世的重褶齿猬（Zalambdalestes lechei）标本保存了几乎完整的颈椎（C2-C7）系列，显示了一个高度变形的颈椎轴（C2）。研究人员采用一种综合方法，结合哺乳动物的比较解剖检查、肌肉重建、几何形态计量学和虚拟运动范围分析，探讨了这种颈椎形态的意义。研究人员利用三维地标分析，将重褶齿猬的颈轴形态与88种哺乳动物（单孔类、有袋类和胎生类）的数据集进行了比较。

结果表明，重褶齿猬独特的轴线形态在现存哺乳动物中没有相似之处。颈部的虚拟运动范围分析强烈暗示了重褶齿猬能够进行非常有力的头部运动，而且对于这种体型的动物来说，它的腹屈程度很高。这些发现揭示了古脊椎动物颈部形态早期演化过程中意想不到的复杂性，并表明重褶齿猬的摄食行为类似于专门从事蚯蚓捕食的食虫动物，其防御行为则类似于现代的多刺哺乳动物。

附：英文原文

Title: The Late Cretaceous eutherian Zalambdalestes reveals unique axis and complex evolution of the mammalian neck

Author: ucja Fostowicz-Frelik e f

Issue&Volume: 2024/04/16

Abstract: The typical mammalian neck consisting of seven cervical vertebrae (C1–C7) was established by the Late Permian in the cynodont forerunners of modern mammals. This structure is precisely adapted to facilitate movements of the head during feeding, locomotion, predator evasion, and social interactions. Eutheria, the clade including crown placentals, has a fossil record extending back more than 125 million years revealing significant morphological diversification in the Mesozoic. Yet very little is known concerning the early evolution of eutherian cervical morphology and its functional adaptations. A specimen of Zalambdalestes lechei from the Late Cretaceous of Mongolia boasts exceptional preservation of an almost complete series of cervical vertebrae (C2–C7) revealing a highly modified axis (C2). The significance of this cervical morphology is explored utilizing an integrated approach combining comparative anatomical examination across mammals, muscle reconstruction, geometric morphometrics and virtual range of motion analysis. We compared the shape of the axis in Zalambdalestes to a dataset of 88 mammalian species (monotremes, marsupials, and placentals) using three-dimensional landmark analysis. The results indicate that the unique axis morphology of Zalambdalestes has no close analog among living mammals. Virtual range of motion analysis of the neck strongly implies Zalambdalestes was capable of exerting very forceful head movements and had a high degree of ventral flexion for an animal its size. These findings reveal unexpected complexity in the early evolution of the eutherian cervical morphology and suggest a feeding behavior similar to insectivores specialized in vermivory and defensive behaviors in Zalambdalestes akin to modern spiniferous mammals.

DOI: 10.1016/j.scib.2024.04.027

Source: https://www.sciencedirect.com/science/article/pii/S2095927324002615