CRANIAL DIMENSIONS AS ESTIMATORS OF BODY MASS AND LOCOMOTOR HABITS IN EXTANT AND FOSSIL RODENTS
CRANIAL DIMENSIONS AS ESTIMATORS OF BODY MASS AND LOCOMOTOR HABITS IN EXTANT AND FOSSIL RODENTS
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DOI：
10.1080/02724634.2015.1014905
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发表时间：
2016-01-02
影响因子：
1.4
通讯作者：
Silcox, Mary T.
中科院分区：
文献类型：
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作者：
Bertrand, Ornella C.;Schillaci, Michael A.;Silcox, Mary T.
估计化石啮齿动物的体重和运动习惯是具有挑战性的类群没有可用的颅后材料。虽然存在根据现存啮齿动物的牙齿尺寸来估计体重的公式，但考虑到现代啮齿动物已经进化出高度专门化的牙齿，这些公式的适用性值得怀疑，而化石分类群通常表现出更少的衍生条件。在本研究中，11颅骨变量从一个样本的203个现存的啮齿类动物的已知体重代表一系列的分类组进行了评估，使用减少主轴（RMA）回归。结果显示，体重与11个颅骨变量中的每一个都有很强的相关性。最好的估计体质量是头骨长度和颊齿面积，而最不可靠的措施是腭长度，枕骨大孔，以及脑壳和枕骨髁的尺寸。我们估计了五个化石Ischyromyidae啮齿动物的标本，身体质量从来没有估计（Paramys copei，P. delicatus，Reithroparamys delicatissimus，Rapamys atramontis和Ischyromys typus）。主成分和典型变量分析的基础上，10颅尺寸的103个成员的松鼠形表明，运动习惯和颅变量之间存在的关系，在这个亚目。在这些分析中，早期ischyromyids都被放置在陆地组与Aprodontia，旱獭，Cynomys，和Spermophilus。这与先前关于早期啮齿动物运动的假设相矛盾，该假设表明它们是树栖的或在习惯上更普遍。
Estimating body mass and locomotor habits of fossil rodents is challenging for taxa without available postcranial material. Although equations exist to estimate body mass from dental dimensions based on extant rodents, the applicability of such equations is doubtful given that modern rodents have evolved highly specialized teeth, whereas fossil taxa often exhibit a much less derived condition. For the present study, 11 cranial variables from a sample of 203 extant rodents of known body mass representing a range of taxonomic groups were assessed using reduced major axis (RMA) regression. The results show a strong correlation between body mass and each of the 11 cranial variables. The best estimators for body mass are skull length and cheek-tooth area, whereas the least reliable measures are palate length, and foramen magnum, as well as braincase and occipital condyle dimensions. We estimated body mass for specimens of five fossil Ischyromyidae rodents for which body mass had never been estimated (Paramys copei, P. delicatus, Reithroparamys delicatissimus, Rapamys atramontis, and Ischyromys typus). Principal components and canonical variates analyses based on 10 cranial dimensions for 103 members of Sciuromorpha demonstrate that a relationship exists between locomotor habits and cranial variables in this suborder. In these analyses, early ischyromyids are all placed in the terrestrial group with Aplodontia, Marmota, Cynomys, and Spermophilus. This contradicts previous hypotheses regarding early rodent locomotion, which suggested that they were arboreal or more generalized in their habits.