University of Toronto Scarborough, Scarborough, ON, M1C 1A4, Canada.
University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada.
Sci Rep. 2024 Aug 2;14(1):17901. doi: 10.1038/s41598-024-68390-y.
While brain size in primates and their relatives within Euarchontoglires is well-studied, less research has examined brain shape, or the allometric trajectories that underlie the relationship between size and shape. Defining these patterns is key to understanding evolutionary trends. 3D geometric morphometric analyses of endocranial shape were performed on 140 species of extant euarchontoglirans using digital cranial endocasts. Principal component analyses on Procrustes shape variables show a clear phylogenetic pattern in endocranial shape, supported by an ANOVA which identified significant differences in shape among several groups (e.g., Platyrrhini, Strepsirrhini, Scandentia, Rodentia, and Lagomorpha). ANOVAs of shape and size also indicate that allometry has a small but significant impact on endocranial shape across Euarchontoglires, with homogeneity of slopes tests finding significant differences in the scaling relationship between shape and size among these same groups. While most of these clades possess a distinct endocranial morphotype, the highly derived platyrrhines display the strongest relationship between size and shape. Rodents show the most diversity in endocranial shape, potentially attributed to their comparatively weak relationship between shape and size. These results suggest fundamental differences in how shape and size covary among Euarchontoglires, which may have facilitated the adaptive radiations that characterize members of this group.
虽然灵长类动物及其在真兽亚纲内的亲缘动物的大脑大小已经得到了很好的研究，但对大脑形状或大小和形状之间关系的比例轨迹的研究较少。定义这些模式是理解进化趋势的关键。使用数字化颅骨内模对 140 种现存的真兽亚纲动物进行了内颅形状的 3D 几何形态测量学分析。基于 Procrustes 形状变量的主成分分析显示内颅形状具有明显的系统发育模式，这一模式得到了方差分析的支持，该分析确定了几个群体之间的形状差异（例如，阔鼻猴亚目、栉趾猴亚目、树鼩目、啮齿目和兔形目）。形状和大小的方差分析也表明，比例关系对真兽亚纲的内颅形状有微小但显著的影响，斜率同质性检验发现这些相同群体之间形状和大小的比例关系存在显著差异。虽然这些进化枝中的大多数都具有独特的内颅形态，但高度衍生的阔鼻猴显示出与大小之间最强的关系。啮齿动物的内颅形状具有最多的多样性，这可能归因于它们在形状和大小之间相对较弱的关系。这些结果表明，真兽亚纲动物中形状和大小的协变存在根本差异，这可能促进了该组特征成员的适应性辐射。
