Granatosky Michael C, Miller Charlotte E, Boyer Doug M, Schmitt Daniel
Department of Evolutionary Anthropology, Duke University, Durham, NC, USA.
Department of Evolutionary Anthropology, Duke University, Durham, NC, USA.
J Hum Evol. 2014 Oct;75:40-52. doi: 10.1016/j.jhevol.2014.06.011. Epub 2014 Sep 10.
Lumbar vertebral morphology has been used as an indicator of locomotor behavior in living and fossil mammals. Rigidity within the lumbar region is thought to be important for increasing overall axial rigidity during various forms of locomotion, including bridging between supports, inverted quadrupedalism, gliding, and flying. However, distinguishing between those behaviors using bony features has been challenging. This study used osteological characters of the lumbar vertebrae to attempt to develop fine-grade functional distinctions among different mammalian species in order to make more complete inferences about how the axial skeleton affects locomotor behavior in extant mammals. These same lumbar characters were measured in two extinct species for which locomotor behaviors are well known, the sloth lemurs (Palaeopropithecus and Babakotia radofilai), in order to further evaluate their locomotor behaviors. Results from a principal components analysis of seven measurements, determined to be functionally significant from previous studies, demonstrate that inverted quadrupeds in the sample are characterized by dorsoventrally short and cranio-caudally expanded spinous processes, dorsally oriented transverse processes, and mediolaterally short and dorsoventrally high vertebral bodies compared with mammals that are relatively pronograde, vertical clingers, or gliders. Antipronograde mammals, dermopterans, and chiropterans also exhibit these traits, but not to the same extent as the inverted quadrupeds. In accordance with previous studies, our data show that the sloth lemur B. radofilai groups closely with antipronograde mammals like lorises, while Palaeopropithecus groups with extant sloths. These findings suggest that Palaeopropithecus was engaged in inverted quadrupedalism at a high frequency, while B. radofilai may have engaged in a more diverse array of locomotor and positional behaviors. The osteological features used here reflect differences in lumbar mobility and suggest that axial rigidity is advantageous for suspensory locomotion and possibly flight in bats.
腰椎形态已被用作现存和化石哺乳动物运动行为的一个指标。腰椎区域的刚性被认为对于在包括支撑间的跨越、倒转四足行走、滑翔和飞行等各种运动形式中增加整体轴向刚性很重要。然而，利用骨骼特征区分这些行为一直具有挑战性。本研究利用腰椎的骨学特征，试图在不同哺乳动物物种之间建立精细的功能区分，以便对轴向骨骼如何影响现存哺乳动物的运动行为做出更完整的推断。为了进一步评估两种已知运动行为的已灭绝物种——懒猴（古原狐猴属和拉氏原狐猴）的运动行为，对同样的腰椎特征进行了测量。对七项测量结果进行主成分分析，这些测量结果在先前研究中被确定具有功能意义，结果表明，与相对前位行走、垂直攀附或滑翔的哺乳动物相比，样本中的倒转四足动物的特征是棘突背腹向短且头尾向扩展、横突背向、椎体内外侧短且背腹向高。反前位行走的哺乳动物、皮翼目动物和翼手目动物也表现出这些特征，但程度不如倒转四足动物。与先前研究一致，我们的数据表明，拉氏原狐猴与懒猴等反前位行走的哺乳动物密切相关，而古原狐猴与现存树懒相关。这些发现表明，古原狐猴频繁进行倒转四足行走，而拉氏原狐猴可能参与了更多样化的运动和姿势行为。这里使用的骨学特征反映了腰椎活动度的差异，并表明轴向刚性对蝙蝠的悬停运动和可能的飞行有利。
