Hautier Lionel, Billet Guillaume, Eastwood Bethany, Lane Jemima
Laboratoire de Paléontologie, Institut des Sciences de l'Evolution de Montpellier, UMR-CNRS 5554, Cc 064, Université de Montpellier 2, place Eugène Bataillon, Montpellier Cedex, France; Museum of Zoology, University of Cambridge, Cambridge, UK.
Anat Rec (Hoboken). 2014 Jun;297(6):979-1008. doi: 10.1002/ar.22916. Epub 2014 Apr 25.
Several studies have shown an increased morphological variability of sloths from mammalian norms, affecting varied phenotypic traits from skeletal parts to soft tissues. We present here the first descriptive comparison of the whole skull morphology within the two extant sloth genera, combining geometric morphometric approaches with comparative anatomy. We used these methods to explore the patterns of the intra- and interspecific morphological variation of the skull with regard to several factors such as phylogeny, geography, allometry, or sexual dimorphism. Our study first revealed strong phylogenetic and geographical imprints on the cranial and mandibular morphological traits. This result demonstrates the importance of accurate knowledge of species and their geographical distributions; here we show from an example pertaining to Bradypus variegatus populations the implications this has on conservation management. Moreover, in order to control the amount of this detected variation, we tentatively compared sloths to a wide range of mammalian species. Our analysis found no significant increase in the average deviation of skull shape within each investigated sloth species compared to other mammals. This suggests that the intraspecific cranial variation in sloths does not depart significantly from the variation observed in other mammals. This result has positive implications for the demarcation of anatomical regions that maintain high levels of morphological variation in sloths.
多项研究表明，树懒的形态与哺乳动物的标准相比变异性增加，影响了从骨骼部分到软组织等各种表型特征。我们在此展示了对两个现存树懒属的整个头骨形态的首次描述性比较，将几何形态测量方法与比较解剖学相结合。我们使用这些方法来探究头骨种内和种间形态变异的模式，涉及系统发育、地理、异速生长或两性异形等多个因素。我们的研究首先揭示了颅骨和下颌形态特征上强烈的系统发育和地理印记。这一结果证明了准确了解物种及其地理分布的重要性；在此我们从一个与鬃毛三趾树懒种群相关的例子中展示了这对保护管理的影响。此外，为了控制检测到的这种变异量，我们尝试将树懒与多种哺乳动物物种进行比较。我们的分析发现，与其他哺乳动物相比，每个被研究的树懒物种头骨形状的平均偏差没有显著增加。这表明树懒种内颅骨变异与在其他哺乳动物中观察到的变异没有显著差异。这一结果对于界定树懒中保持高度形态变异的解剖区域具有积极意义。
