Reconstructing the mass and thermal ecology of North American Pleistocene tortoises

Researchers often interpret the presence of tortoises in Pleistocene assemblages as evidence of an interglacial age, based on an assumption that these fossils indicate thermic climates, as modern giant tortoises require. Since the Paleocene, tortoises have been common components of terrestrial fossil assemblages and have repeatedly evolved species of giant size. Whereas extant giant tortoises are found only on islands off the coasts of South America and Africa, at least two species persisted in North America until the terminal Pleistocene. These tortoises, Hesperotestudo crassiscutata and Gopherus ‘hexagonatus,’ both of which reached carapace lengths of >1m, were distributed across the southern United States. This study provides new metrics to derive quantitative weight estimates from measurements of the tortoise shell. The linear measurement of 69 anatomical features of the shell of 108 live tortoises indicate that the regression between straight carapace length and weight is most s...

研究人员常将更新世（Pleistocene）化石组合中陆龟的存在解读为间冰期的证据，这一结论基于一项假设：正如现代巨型陆龟所需的生存环境那样，这些化石指示了温暖气候。自古新世（Paleocene）以来，陆龟一直是陆地化石组合中的常见类群，并多次演化出巨型物种。现存巨型陆龟仅分布于南美洲和非洲沿岸的岛屿，但至少有两个物种在北美存续至更新世末期。这两个物种分别是厚鳞陆龟（Hesperotestudo crassiscutata）和六边形陆龟（Gopherus 'hexagonatus'），二者的背甲（carapace）长度均超过1米，曾广泛分布于美国南部。本研究提供了全新的量化方法，可通过陆龟壳体的测量数据推导其体重估算值。研究人员对108只活体陆龟的69项壳体解剖特征进行了线性测量，结果显示，背甲直线长度与体重之间的回归关系最为……