Extrapolating body masses in large terrestrial vertebrates
Extrapolating body masses in large terrestrial vertebrates
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DOI：
10.1017/pab.2017.9
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发表时间：
2017-11-01
期刊：
影响因子：
2.7
通讯作者：
Campione, Nicols E.
中科院分区：
文献类型：
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作者：
Campione, Nicols E.
尽管超过世纪的兴趣，身体质量估计在化石记录仍然存在争议，特别是当估计身体质量的类群以外的大小范围的活动物。一种估计方法是使用从现存（活的）陆生脊椎动物收集的肱骨和股骨（茎突）周长，通过比例模型来推断灭绝的四足动物的体重。当应用于非常大的灭绝类群，基于外显的缩放方法招致明显的方法外推导致一些人认为，他们可能高估了大型陆生脊椎动物的身体质量。在这里，我测试这样的断言隐含的假设：二次模型提供了一个更好的适合合并肱骨和股骨周长与身体质量的关系。然后，我检查这些模型的外推潜力，通过一系列的子集练习，其中较低的身体质量集被用来估计较大的集。模型拟合恢复了对原始线性模型的更大支持，并且不显著的二次项表明二次关系是统计线性的。尽管如此，一些统计支持二次模型，并应用二次模型的一系列恐龙提供较低的质量估计在较大的尺寸，更符合最近的估计使用最小凸壳（MCH）的方法。考虑到这种一致性，此时可能首选二次模型。不过，还是要谨慎;与线性函数相比，二次函数的外推是不可预测的。测试妇幼保健方法的进一步研究（例如，通用放大因子的使用）可以揭示组合的股骨和肱骨周长与体重之间的关系的线性与二次性质。
Despite more than a century of interest, body-mass estimation in the fossil record remains contentious, particularly when estimating the body mass of taxa outside the size scope of living animals. One estimation approach uses humeral and femoral (stylopodial) circumferences collected from extant (living) terrestrial vertebrates to infer the body masses of extinct tetrapods through scaling models. When applied to very large extinct taxa, extant-based scaling approaches incur obvious methodological extrapolations leading some to suggest that they may overestimate the body masses of large terrestrial vertebrates. Here, I test the implicit assumption of such assertions: that a quadratic model provides a better fit to the combined humeral and femoral circumferences-to-body mass relationship. I then examine the extrapolation potential of these models through a series of subsetting exercises in which lower body-mass sets are used to estimate larger sets. Model fitting recovered greater support for the original linear model, and a nonsignificant second-degree term indicates that the quadratic relationship is statistically linear. Nevertheless, some statistical support was obtained for the quadratic model, and application of the quadratic model to a series of dinosaurs provides lower mass estimates at larger sizes that are more consistent with recent estimates using a minimum convex-hull (MCH) approach. Given this consistency, a quadratic model may be preferred at this time. Still, caution is advised; extrapolations of quadratic functions are unpredictable compared with linear functions. Further research testing the MCH approach (e.g., the use of a universal upscaling factor) may shed light on the linear versus quadratic nature of the relationship between the combined femoral and humeral circumferences and body mass.