Convergence and functional evolution of longirostry in crocodylomorphs
Convergence and functional evolution of longirostry in crocodylomorphs
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DOI：
10.1111/pala.12432
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发表时间：
2019-11-01
期刊：
影响因子：
2.6
通讯作者：
Rayfield, Emily J.
中科院分区：
文献类型：
--
作者：
Ballell, Antonio;Moon, Benjamin C.;Rayfield, Emily J.
在中生代，鳄形动物的分类和形态多样性比今天高得多。一个特别成功的分支，Thalattosuchia，以长鼻著称：长而细的鼻子。人们普遍认为，Thalattosuchia的成功在一定程度上要归功于长寿的进化，这导致了一种与现存的印度大鳄Gavialis相似的捕食生态。在这里，我们使用颅骨肌肉骨骼解剖和有限元模型的数字重建来比较thalattosuchian Pelagosaurus和Gavialis头骨的形状和功能，以表明它们具有不同的颌骨肌肉排列和生物力学行为。此外，通过在可变速率模型下进行进化速率分析，研究了鳄鱼进化支系辐射中与进食相关的下颌性状与长寿的相关性。我们发现，尽管伯龙和鸽龙头骨上的应力分布模式相似，但前者的机械阻力更低。这表明，与Gavialis相比，Pelagosaurus无法处理大型的，机械上不易驾驭的猎物，而是作为一种专门的鱼食动物，以柔软的，较小的猎物为食。其次，通过下颌骨功能特征的速率加速实现了进食策略的创新，这是某些分支如thalattosuchans和eusuchans多样化的关键机制。不同的功能进化速率表明侏罗纪远龙类和巨龙类的多样化动态存在差异。
During the Mesozoic, Crocodylomorpha had a much higher taxonomic and morphological diversity than today. Members of one particularly successful clade, Thalattosuchia, are well-known for being longirostrine: having long, slender snouts. It has generally been assumed that Thalattosuchia owed their success in part to the evolution of longirostry, leading to a feeding ecology similar to that of the living Indian gharial, Gavialis. Here, we compare form and function of the skulls of the thalattosuchian Pelagosaurus and Gavialis using digital reconstructions of the skull musculoskeletal anatomy and finite element models to show that they had different jaw muscle arrangements and biomechanical behaviour. Additionally, the relevance of feeding-related mandibular traits linked to longirostry in the radiation of crocodylomorph clades was investigated by conducting an evolutionary rates analysis under the variable rates model. We find that, even though Pelagosaurus and Gavialis share similar patterns of stress distribution in their skulls, the former had lower mechanical resistance. This suggests that compared to Gavialis, Pelagosaurus was unable to process large, mechanically less tractable prey, instead operating as a specialized piscivore that fed on softer and smaller prey. Secondly, innovation of feeding strategies was achieved by rate acceleration of functional characters of the mandible, a key mechanism for the diversification of certain clades like thalattosuchians and eusuchians. Different rates of functional evolution suggest divergent diversification dynamics between teleosaurids and metriorhynchids in the Jurassic.