División Antropología (FCNyM-UNLP), CONICET, La Plata, Argentina.
Institut de biologie de l'Ecole normale supérieure (IBENS), Ecole normale supérieure, CNRS, INSERM, PSL Université Paris, Paris, France.
Am J Phys Anthropol. 2019 Jun;169(2):322-331. doi: 10.1002/ajpa.23837. Epub 2019 Apr 10.
Platyrrhines constitute a diverse clade, with the modern Atelidae exhibiting the most variation in cranial and endocast morphology. The processes responsible for this diversification are not well understood. Here, we present a geometric morphometric study describing variation in cranial and endocranial shape of 14 species of Alouatta, Ateles, Brachyteles, and Lagothrix and two extinct taxa, Cartelles and Caipora.
We examined cranial and endocranial shape variation among species using images reconstructed from CT scans and geometric morphometric techniques based on three-dimensional landmarks and semilandmarks. Principal components analyses were used to explore variation, including the Procrustes shape coordinates, summing the logarithm of the Centroid Size, the common allometric component, and residual shape components.
Differences in endocranial shape are related to a relative increase or decrease in the volume of the neocortex region with respect to brainstem and cerebellum regions. The relative position of the brainstem varies from a posterior position in Alouatta to a more ventral position in Ateles. The shape of both the cranium and endocast of Caipora is within the observed variation of Brachyteles. Cartelles occupies the most differentiated position relative to the extant taxa, especially in regards to its endocranial shape.
The pattern of variation in the extant species in endocranial shape is similar to the variation observed in previous cranial studies, with Alouatta as an outlier. The similarities between Caipora and Brachyteles were unexpected and intriguing given the frugivorous adaptations inferred from the fossil's dentition. Our study shows the importance of considering both extant and fossil species when studying diversification of complex traits.
阔鼻猴类是一个多样化的分支，现代卷尾猴科在颅骨和内颅骨形态上表现出最多的变异。导致这种多样化的过程尚不清楚。在这里，我们进行了一项几何形态测量学研究，描述了 14 种吼猴、绒毛猴、绒毛蛛猴和绒毛狨以及两个已灭绝的分类群——卡泰尔和卡波拉的颅骨和内颅骨形状的变异。
我们使用来自 CT 扫描的重建图像和基于三维标志和半标志的几何形态测量技术，检查了物种之间的颅骨和内颅骨形状变化。主成分分析用于探索变异，包括 Procrustes 形状坐标、CentroidSize 的对数求和、常见的异速成分和剩余形状成分。
内颅骨形状的差异与新皮质区域相对于脑干和小脑区域的相对增加或减少有关。脑干的相对位置从吼猴的后部位置到绒毛猴的更腹侧位置变化。颅骨和内颅骨的形状卡波拉都在绒毛蛛猴观察到的变异范围内。卡泰尔相对于现存分类群的位置最为分化，尤其是在内颅骨形状方面。
现存物种在内颅骨形状上的变异模式与之前颅骨研究中观察到的变异模式相似，吼猴是一个异常值。卡波拉与绒毛蛛猴之间的相似之处令人意外和有趣，因为从化石的牙齿推断出它们是食果动物。我们的研究表明，在研究复杂特征的多样化时，考虑现存和化石物种非常重要。
