Crocodylomorph cranial shape evolution and its relationship with body size and ecology
Crocodylomorph cranial shape evolution and its relationship with body size and ecology
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DOI：
10.1111/jeb.13540
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发表时间：
2019-09-30
影响因子：
2.1
通讯作者：
Godoy, Pedro L.
中科院分区：
文献类型：
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作者：
Godoy, Pedro L.
鳄形目，包括现存的鳄鱼和它们已灭绝的近亲，拥有丰富的化石记录，可以追溯到2亿多年前。与现代的半水生鳄鱼不同，灭绝的鳄形动物表现出更多样化的生活方式，从海洋到完全陆地的形式。这种生态多样性反映在显著的形态差异上，特别是在颅骨形态方面，这似乎与该群体的生态角色密切相关。在这里，我使用几何形态计量学来全面研究鳄鱼的颅形变化和差异。我定量地评估了颅骨形状与生态（即陆地、水生和半水生生活方式）之间的关系，以及可能的异速生长形状变化。我还描述了颅骨形状演变的模式，并确定了政权的转变。我发现形状和大小之间有很强的联系，生态对观察到的形状变化有很大的影响。陆生分类群，特别是notosuchians，具有明显更高的差异，并且与大型水生或半水生物种相关的转向更长的体型。这证明了鳄形动物进化史中颅形、体型和生活方式之间的复杂关系。此外，时间差异分析对不同的系统发育假设高度敏感，表明不同树木之间的总体模式描述。对于鳄鱼形目动物，大多数结果都一致认为，早侏罗世和白垩纪中期分别出现了一个早期高峰和另一个高峰，随后几乎持续下降，直到今天。由于只有冠类动物存活了整个新生代，这种差异的减少很可能是栖息地丧失的结果，栖息地丧失缩小了鳄形动物的生活方式范围。
Crocodylomorpha, which includes living crocodylians and their extinct relatives, has a rich fossil record, extending back for more than 200 million years. Unlike modern semi-aquatic crocodylians, extinct crocodylomorphs exhibited more varied lifestyles, ranging from marine to fully terrestrial forms. This ecological diversity was mirrored by a remarkable morphological disparity, particularly in terms of cranial morphology, which seems to be closely associated with ecological roles in the group. Here, I use geometric morphometrics to comprehensively investigate cranial shape variation and disparity in Crocodylomorpha. I quantitatively assess the relationship between cranial shape and ecology (i.e. terrestrial, aquatic, and semi-aquatic lifestyles), as well as possible allometric shape changes. I also characterize patterns of cranial shape evolution and identify regime shifts. I found a strong link between shape and size, and a significant influence of ecology on the observed shape variation. Terrestrial taxa, particularly notosuchians, have significantly higher disparity, and shifts to more longirostrine regimes are associated with large-bodied aquatic or semi-aquatic species. This demonstrates an intricate relationship between cranial shape, body size and lifestyle in crocodylomorph evolutionary history. Additionally, disparity-through-time analyses were highly sensitive to different phylogenetic hypotheses, suggesting the description of overall patterns among distinct trees. For crocodylomorphs, most results agree in an early peak during the Early Jurassic and another in the middle of the Cretaceous, followed by nearly continuous decline until today. Since only crown-group members survived through the Cenozoic, this decrease in disparity was likely the result of habitat loss, which narrowed down the range of crocodylomorph lifestyles.