Evidence for endothermic ancestors of crocodiles at the stem of archosaur evolution
Evidence for endothermic ancestors of crocodiles at the stem of archosaur evolution
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DOI：
10.1086/422766
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发表时间：
2004-11-01
影响因子：
1.6
通讯作者：
Grigg, GC
中科院分区：
文献类型：
--
作者：
Seymour, RS;Bennett-Stamper, CL;Grigg, GC
鳄鱼心脏的生理、解剖和发育特征支持了古生物学证据，即活鳄鱼的祖先是活跃的和吸热的，但当它侵入水生埋伏捕食者生态位时，该谱系恢复为外温性。在恒温动物中，高代谢率、高血流量和四腔心脏中高体循环血压与低肺循环血压的完全分离之间存在功能联系。外温动物通常缺乏所有这些特征，但鳄鱼保留了一个四室心脏。然而，鳄鱼有一个神经控制的，肺动脉旁路分流，是功能在潜水。分流发生在心脏外部，涉及起源于右心室的左主动脉弓、左主动脉弓和右主动脉弓之间的Panizza孔以及肺动脉基部的锯齿瓣。发育研究表明，所有这些独特的鳄鱼的功能是二次派生，表明从完全分离的血液流动的恒温动物的控制分流的外温动物的转变。我们提出了其他的证据，在茎主龙的恒温，并建议，一些恐龙可能继承了性状。
Physiological, anatomical, and developmental features of the crocodilian heart support the paleontological evidence that the ancestors of living crocodilians were active and endothermic, but the lineage reverted to ectothermy when it invaded the aquatic, ambush predator niche. In endotherms, there is a functional nexus between high metabolic rates, high blood flow rates, and complete separation of high systemic blood pressure from low pulmonary blood pressure in a four-chambered heart. Ectotherms generally lack all of these characteristics, but crocodilians retain a four-chambered heart. However, crocodilians have a neurally controlled, pulmonary bypass shunt that is functional in diving. Shunting occurs outside of the heart and involves the left aortic arch that originates from the right ventricle, the foramen of Panizza between the left and right aortic arches, and the cog-tooth valve at the base of the pulmonary artery. Developmental studies show that all of these uniquely crocodilian features are secondarily derived, indicating a shift from the complete separation of blood flow of endotherms to the controlled shunting of ectotherms. We present other evidence for endothermy in stem archosaurs and suggest that some dinosaurs may have inherited the trait.