McCurry Matthew R, Evans Alistair R, Fitzgerald Erich M G, Adams Justin W, Clausen Philip D, McHenry Colin R
Monash Biomedicine Discovery Institute and Centre for Human Anatomy Education, Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC, Australia
Geosciences, Museums Victoria, Melbourne, VIC, Australia.
Proc Biol Sci. 2017 Mar 15;284(1850). doi: 10.1098/rspb.2016.2348.
The striking resemblance of long-snouted aquatic mammals and reptiles has long been considered an example of morphological convergence, yet the true cause of this similarity remains untested. We addressed this deficit through three-dimensional morphometric analysis of the full diversity of crocodilian and toothed whale (Odontoceti) skull shapes. Our focus on biomechanically important aspects of shape allowed us to overcome difficulties involved in comparing mammals and reptiles, which have fundamental differences in the number and position of skull bones. We examined whether diet, habitat and prey size correlated with skull shape using phylogenetically informed statistical procedures. Crocodilians and toothed whales have a similar range of skull shapes, varying from extremely short and broad to extremely elongate. This spectrum of shapes represented more of the total variation in our dataset than between phylogenetic groups. The most elongate species (river dolphins and gharials) are extremely convergent in skull shape, clustering outside of the range of the other taxa. Our results suggest the remarkable convergence between long-snouted river dolphins and gharials is driven by diet rather than physical factors intrinsic to riverine environments. Despite diverging approximately 288 million years ago, crocodilians and odontocetes have evolved a remarkably similar morphological solution to feeding on similar prey.
长鼻水生哺乳动物和爬行动物之间惊人的相似性长期以来一直被视为形态趋同的一个例子，然而这种相似性的真正原因仍未得到验证。我们通过对鳄鱼和齿鲸（鲸目齿鲸亚目）头骨形状的全多样性进行三维形态测量分析来解决这一不足。我们对形状在生物力学方面的重要方面的关注使我们能够克服比较哺乳动物和爬行动物所涉及的困难，因为它们在头骨骨骼的数量和位置上存在根本差异。我们使用系统发育信息统计程序研究了饮食、栖息地和猎物大小是否与头骨形状相关。鳄鱼和齿鲸的头骨形状范围相似，从极短且宽到极长。在我们的数据集中，这种形状谱所代表的总变异比系统发育组之间的更多。最细长的物种（淡水豚和印度食鱼鳄）在头骨形状上极其趋同，聚集在其他分类群范围之外。我们的结果表明，长鼻淡水豚和印度食鱼鳄之间显著的趋同是由饮食驱动的，而不是河流环境固有的物理因素。尽管鳄鱼和齿鲸在大约2.88亿年前就已经分化，但它们在以相似猎物为食方面进化出了非常相似的形态学解决方案。
