How to Make a Bird Skull: Major Transitions in the Evolution of the Avian Cranium, Paedomorphosis, and the Beak as a Surrogate Hand
How to Make a Bird Skull: Major Transitions in the Evolution of the Avian Cranium, Paedomorphosis, and the Beak as a Surrogate Hand
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DOI：
10.1093/icb/icw069
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发表时间：
2016-09-01
影响因子：
2.6
通讯作者：
Hoffman, Eva
中科院分区：
文献类型：
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作者：
Bhullar, Bhart-Anjan S.;Hanson, Michael;Hoffman, Eva
鸟类的头骨在结构和功能上都很独特。鸟类的许多解剖学多样性都表现在喙上；但是喙本身，主要是由前颌骨形成的，长在一个短脸和一个球根状的、增大的脑壳上。在这里，我们使用原始的解剖观察和重建来描述鸟类头骨在更大背景下的整体形式，并提供从早期恐龙头骨（一种大型食肉动物的头骨）到现代鸟类头骨的进化转变的一般说明。面部缩短，脑周围增大的脑壳（随之而来的是眶周元素和内收腔的缩小），以及骨骼普遍变薄和关节疏松是趋势。其中许多都归因于幼年化或幼体发育，这一点从幼年早期兽脚亚目动物（Coelophysis）与早期鸟类（如始祖鸟）的比较中得到了充分的证明。在鸟冠附近，前触须急剧增大，并融入鸟类特有的移动动力系统。我们假设，在颅骨上增加一个大的元素可能只是因为面部的儿童型缩短而在生物力学上可行；喙的运动仅仅是因为幼体骨的变薄和关节的松动，而在腔骨发育成熟的过程中则相反。最后，喙本身变得复杂的手被整合到翅膀。鸟类的啄食和灵长类动物的抓握在结构、运动和神经学上都有相似之处。在复杂而贫瘠的环境中精确选择高质量食物的能力，可能使冠鸟在白垩纪末期的大灾难中幸存下来，在食物网的高营养水平崩溃后，它们以昆虫、种子和其他碎屑为食。
The avian skull is distinctive in its construction and in its function. Much of bird anatomical variety is expressed in the beak; but the beak itself, largely formed of the premaxillary bone, is set upon a shortened face and a bulbous, enlarged braincase. Here, we use original anatomical observations and reconstructions to describe the overall form of the avian skull in a larger context and to provide a general account of the evolutionary transformation from the early dinosaur skull-the skull of an archosaurian macropredator- to that of modern birds. Facial shortening, the enlargement of the braincase around an enlarged brain (with consequential reduction of circumorbital elements and the adductor chamber), and general thinning and looser articulation of bones are trends. Many of these owe to juvenilization or paedomorphosis, something that is abundantly evident from comparison of a juvenile early theropod (Coelophysis) to early avialans like Archaeopteryx. Near the avian crown, the premaxilla becomes dramatically enlarged and integrated into the characteristic mobile kinetic system of birds. We posit that this addition of a large element onto the skull may be biomechanically feasible only because of the paedomorphic shortening of the face; and kinesis of the beak only because of the paedomorphic thinning of the bones and loosening of articulations, as played out in reverse during the maturation of Coelophysis. Finally, the beak itself becomes elaborated as the hands are integrated into the wing. There are structural, kinematic, and neurological similarities between avian pecking and primate grasping. The ability to precision-select high-quality food against a complex but depauperate background may have permitted crown birds to survive the end-Cretaceous cataclysm by feeding on insects, seeds, and other detritus after the collapse of higher trophic levels in the food web.