Shell geometry and habitat determination in extinct and extant turtles (Reptilia: Testudinata)
Shell geometry and habitat determination in extinct and extant turtles (Reptilia: Testudinata)
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DOI：
10.1666/10052.1
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发表时间：
2011-09-01
期刊：
影响因子：
2.7
通讯作者：
Reisz, Robert R.
中科院分区：
文献类型：
--
作者：
Benson, Roger B. J.;Domokos, Gabor;Reisz, Robert R.
包括前肢比例和甲骨组织学在内的多种手段被用来推断灭绝龟的古生态。然而，炮弹的高宽比（作为单参数炮弹模型）由于其不可靠性而被忽略，而且炮弹几何结构的更复杂方面通常被忽视。在这里，我们使用一个更可靠的，三参数的几何模型的壳轮廓在前视图作为一种手段来评估海龟的古生态。在区分陆生、半水生和水生三种生态类别时，基于三参数壳模型的现存龟生态预测精度与前肢比例预测精度相当。在区分两类海龟（陆生和非陆生）时，可以获得更高的准确性，因为水生和半水生海龟的轮廓通常非常相似。我们的模型将罗布斯塔元龟（一种来自德国晚三叠世的干龟）归类为非陆生动物，可能是半水生动物。我们的方法，结合基于肢体比例的推断，表明晚三叠世茎龟所代表的生态类型范围广泛。这意味着茎类龟的生态多样化可能是快速的，或者在晚三叠世龟茎类的第一个化石出现之前，有一段相当长的时间是目前隐蔽的多样化。
A variety of means, including forelimb proportions and shell bone histology have been used to infer the paleoecology of extinct turtles. However, the height-to-width ratio of the shell (as a one-parameter shell model) has been dismissed because of its unreliability, and more complex aspects of shell geometry have generally been overlooked. Here we use a more reliable, three-parameter geometric model of the shell outline in anterior view as a means to assess turtle paleoecology. The accuracy of predictions of extant turtle ecology based on our three-parameter shell model is comparable to that derived from forelimb proportions when distinguishing between three ecological classes (terrestrial, semiaquatic, and aquatic). Higher accuracy is obtained when distinguishing between two classes (terrestrial and non-terrestrial), because the contours of aquatic and semiaquatic turtles are often very similar. Our model classifies Proterochersis robusta, a stem turtle from the Late Triassic of Germany, as non-terrestrial, and likely semiaquatic. Our method, combined with inferences based on limb proportions, indicates a diverse range of ecotypes represented by Late Triassic stem turtles. This implies that the ecological diversification of stem-group turtles may have been rapid, or that a substantial period of currently cryptic diversification preceded the first fossil appearance of the turtle stem lineage during the Late Triassic.