Sección Mastozoología, División Zoología Vertebrados, Facultad de Ciencias Naturales y Museo, La Plata, Argentina.
J Anat. 2011 Aug;219(2):167-75. doi: 10.1111/j.1469-7580.2011.01391.x. Epub 2011 May 11.
Among the ecomorphologically diverse Octodontoidea rodents, fossorial habits are prevalent in Ctenomyidae and Octodontidae and occur in some members of Echimyidae. To detect traits linked to scratch-digging, we analyzed morpho-structural variation in the carpus and metacarpus of 27 species of extinct and living octodontoids with epigean, fossorial and subterranean habits. Within a context of relative morphological uniformity, we detected the following specialized traits in the burrowing Clyomys (Echimyidae), Spalacopus (Octodontidae), Ctenomys and †Eucelophorus (Ctenomyidae): broad shortened carpus, robust metacarpals, markedly broad and short metacarpal V, and predominance of ray III (mesaxony, incipient in Spalacopus). In addition, the specialized subterranean Ctenomys presented an enlarged scapholunar in extensive contact with the unciform, and with a complex-shaped proximal articular surface. These features are interpreted as responses to mechanical requirements of scratch-digging, providing greater carpal rigidity and resistance to direct forces exerted during the digging stroke. In Ctenomys, the radius-scapholunar joint restricts movement at wrist level. The phylogenetic distribution of traits shows that the most derived carpal and metacarpal morphologies occur among subterranean octodontoids, also possessing important craniodental adaptations, and supports the hypothesis that the acquisition of digging specializations would have been linked to increasing burrowing frequency in some lineages. Nevertheless, octodontoids with less morphological specializations have metacarpal modifications advantageous for digging, suggesting that scratch-digging specialization preceded the acquisition of tooth-digging traits, in agreement with the general claim that scratch-digging is the primary digging strategy in burrowing mammals.
在形态多样的八齿鼠科啮齿动物中，挖掘洞穴的习性在栉鼠科和八齿鼠科中较为普遍，在一些袋鼩科成员中也存在。为了检测与挖掘相关的特征，我们分析了具有地面生活、穴居和地下生活习性的 27 种已灭绝和现存八齿鼠科动物的腕掌部形态结构变化。在相对形态均匀的背景下，我们在挖掘的栉鼠（袋鼩科）、沙鼠（八齿鼠科）、栉鼠和 †Eucelophorus（栉鼠科）中发现了以下专门的特征：腕骨变宽变短，掌骨粗壮，第 V 掌骨明显变宽变短，第 III 指（中轴型，在沙鼠中刚开始出现）占主导地位。此外，专门的地下栉鼠表现出与尺骨广泛接触并具有复杂形状的近端关节面的增大的舟月骨。这些特征被解释为对挖掘过程中机械需求的反应，提供了更大的腕骨刚性和对挖掘冲程中施加的直接力的抵抗力。在栉鼠中，桡骨-舟月骨关节限制了腕部的运动。特征的系统发生分布表明，最衍生的腕掌部形态出现在地下八齿鼠科中，它们还具有重要的颅面适应，支持了这样的假设，即挖掘专门化的获得可能与某些谱系中挖掘频率的增加有关。然而，具有较少形态专门化的八齿鼠科动物具有有利于挖掘的掌骨变化，这表明挖掘专门化先于牙齿挖掘特征的获得，这与挖掘是挖掘哺乳动物的主要挖掘策略的一般说法一致。
