Data from: Functional morphological adaptations of the bony labyrinth in marsupials (Mammalia, Theria)

Diprotodontia represents the largest and ecologically most distinct order of marsupials occurring in Australasian being highly divers in size, locomotion, habitat preferences, feeding, and activity pattern. The spatial orientation in the habitat and therefore the three-dimensional space is detected by the vestibular system of the inner ear, more precisely by the three semicircular canals. In this study, we investigated the bony labyrinth of diprotodontian and selected non-diprotodontian marsupial mammals of almost all genera with noninvasive micro-CT scanning and 3D-reconstructions. In principal component analyses, the subterranean taxon can be separated from gliding and saltatorial taxa, whereas arboreal species can be separated from saltatorial specimens. The highest loadings of this functional distinction are clearly found in the diameter of the semicircular canals, whereas the overall shape (height, width, length) of the semicircular canals is less important. Additionally, the investigated arboreal and fossorial species of South America are nested in the morphospace of the Australasian taxa. Even if a phylogenetic signal in the anatomy of the bony labyrinth cannot be excluded entirely, the main functional morphological signal of the vestibular system is found in the diameter of the semicircular canals. With the large dataset of extant marsupial mammals analysed here, the locomotion mode of extinct taxa can be inferred in future studies independent of any evidence of postcranial material.

双门齿目（Diprotodontia）是大洋洲分布的有袋类中体型最大、生态特征最独特的类群，其在体型、运动方式、生境偏好、食性以及活动节律上均展现出极高的多样性。动物在生境中的空间定位，亦即对三维空间的感知，由内耳的前庭系统完成，更确切地说是通过三条半规管实现。本研究通过无创显微CT扫描（micro-CT）与三维重建技术，对几乎所有属的双门齿类及部分非双门齿类有袋类哺乳动物的骨性迷路（bony labyrinth）进行了分析。主成分分析结果显示，地下掘栖类群可与滑翔类及跳跃类类群区分开来，而树栖类物种也可与跳跃类标本区分开。该功能区分的最高载荷显著集中于半规管的管径，而半规管的整体形态（高度、宽度、长度）的影响相对较弱。此外，本次研究涉及的南美洲树栖与掘穴类物种，其形态空间（morphospace）嵌套于大洋洲类群的形态空间范围内。尽管无法完全排除骨性迷路解剖结构中存在系统发育信号（phylogenetic signal）的可能性，但前庭系统的主要功能形态学信号仍集中于半规管的管径。基于本次分析的现存有袋类哺乳动物大型数据集，未来研究可在无需颅后骨骼（postcranial material）相关证据的前提下，推断已灭绝类群的运动模式。