Regional endothermy as a trigger for gigantism in some extinct macropredatory sharks
Regional endothermy as a trigger for gigantism in some extinct macropredatory sharks
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DOI：
10.1371/journal.pone.0185185
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发表时间：
2017-09-22
期刊：
影响因子：
3.7
通讯作者：
Ferron, Humberto G.
中科院分区：
文献类型：
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作者：
Ferron, Humberto G.
耳齿鲨科包括一些曾经生活过的最大的大型掠食性鲨鱼，最极端的例子是耳齿鲨（Megaselachus）megalodon。鲸类的洄游、分布格局和灭绝的原因与古近纪的气候因素、鲸类的进化、辐射和迁徙有关。然而，大多数这些先前的建议是基于耳齿类作为变温鲨鱼的想法，而不管这意味着生态，能量和身体大小的限制。有趣的是，最近的一些研究表明这些鲨鱼可能存在内温性，从而为一系列新的解释打开了大门。因此，这项工作提出，区域性恒温存在于耳齿类和一些密切相关的类群（cretoxyrhinids），发挥了重要的作用，在进化中的multitism，并在允许一个积极的生活方式。在这些群体中存在的区域吸热在这里支持三种不同的方法，包括基于同位素的近似，游泳速度推断和应用一种新的方法来评估能源预算和成本的游泳灭绝类群。此外，这一发现具有更广泛的影响。它质疑一些以前的古温度估计部分基于这些类群，表明现有的假设区域内温鱼类的进化需要修改，并提供了关键证据，了解主动macropareparteries的进化。
Otodontids include some of the largest macropredatory sharks that ever lived, the most extreme case being Otodus (Megaselachus) megalodon. The reasons underlying their gigantism, distribution patterns and extinction have been classically linked with climatic factors and the evolution, radiation and migrations of cetaceans during the Paleogene. However, most of these previous proposals are based on the idea of otodontids as ectothermic sharks regardless of the ecological, energetic and body size constraints that this implies. Interestingly, a few recent studies have suggested the possible existence of endothermy in these sharks thus opening the door to a series of new interpretations. Accordingly, this work proposes that regional endothermy was present in otodontids and some closely related taxa (cretoxyrhinids), playing an important role in the evolution of gigantism and in allowing an active mode of live. The existence of regional endothermy in these groups is supported here by three different approaches including isotopic-based approximations, swimming speed inferences and the application of a novel methodology for assessing energetic budget and cost of swimming in extinct taxa. In addition, this finding has wider implications. It calls into question some previous paleotemperature estimates based partially on these taxa, suggests that the existing hypothesis about the evolution of regional endothermy in fishes requires modification, and provides key evidence for understanding the evolution of gigantism in active macropredators.