Evolution of archosaurian body plans: skeletal adaptations of an air-sac-based breathing apparatus in birds and other archosaurs.
Evolution of archosaurian body plans: skeletal adaptations of an air-sac-based breathing apparatus in birds and other archosaurs.
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DOI：
10.1002/jez.548
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发表时间：
2009-10
期刊：
影响因子：
--
通讯作者：
P. O’Connor
中科院分区：
文献类型：
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作者：
P. O’Connor
活着的鸟类是现存的唯一一种肺气囊使颅后骨骼充气的蜥蜴类动物。在这方面值得注意的是，物种的变异性非常大，从完全充气的物种到以整个后颅骨中的空气为特征的物种。尽管许多因素(例如，身体大小)与“相对”气密性有关，但对这一系统的比较研究仍然很少。这个项目试图(1)描述远亲新种鸟骨骼充气性的全身模式，以及(2)评估相对充气性、身体大小和运动专业性之间的假定关系。建立了代表10个较高级别组的52个物种的气动特征曲线。尽管比较显示了大多数较低级别的分支中相对保守的模式，但表面的大小和运动阈值确实会带来可预测的偏离分支规范的偏差。例如，最大的飞鸟(秃鹫、鹈鹕)相对于其各自分支的较小成员表现出高度充气性(即远端肢体的充气性)。相比之下，骨骼充气性在潜水专家(例如企鹅、海雀)的多个谱系中独立消失。对已灭绝的始祖龙的气压性描述揭示了类似的体型进化趋势，特别是在研究不同大小的翼龙(会飞的“爬行动物”)组合中的气压性模式时。作为一种基本的组织系统，骨骼充气性可能通过允许体积增加而不伴随体重增加而在放松对身体大小进化的限制方面发挥作用。这不仅可能对利用耗费能源的空中环境的类群(鸟类、翼龙)至关重要，而且可能对任何大型陆生脊椎动物(如恐龙)有利。
Living birds represent the only extant sauropsid group in which pulmonary air sacs pneumatize the postcranial skeleton. Notable in this regard is an extraordinary degree of variability, ranging from species that are completely apneumatic to those characterized by air within the entire postcranial skeleton. Although numerous factors (e.g., body size) have been linked with "relative" pneumaticity, comparative studies examining this system remain sparse. This project sought to (1) characterize whole-body patterns of skeletal pneumaticity in distantly related neognath birds and (2) evaluate putative relationships among relative pneumaticity, body size and locomotor specializations. Pneumaticity profiles were established for 52 species representing 10 higher-level groups. Although comparisons reveal relatively conserved patterns within most lower-level clades, apparent size- and locomotor-thresholds do impart predictable deviations from the clade norm. For example, the largest flying birds (vultures, pelicans) exhibit hyperpneumaticity (i.e., pneumaticity of distal limb segments) relative to smaller members of their respective clades. In contrast, skeletal pneumaticity has been independently lost in multiple lineages of diving specialists (e.g., penguins, auks). The application of pneumaticity profiling to extinct archosaurs reveals similar trends in body size evolution, particularly when examining patterns of pneumaticity in a size-diverse assemblage of pterosaurs (flying "reptiles"). As a fundamental organizing system, skeletal pneumaticity may play a role in relaxing constraints on body size evolution by allowing volumetric increases without concomitant increases in body mass. Not only might this be critical for taxa (birds, pterosaurs) exploiting the energetically costly aerial environment, but could be beneficial for any large-bodied terrestrial vertebrates such as the dinosaurs.