Data from: A multivariate approach to infer locomotor modes in Mesozoic mammals

Ecomorphological diversity of Mesozoic mammals was presumably constrained
by selective pressures imposed by contemporary vertebrates. In accordance,
Mesozoic mammals for a long time had been viewed as generalized,
terrestrial, small-bodied forms with limited locomotor specializations.
Recent discoveries of Mesozoic mammal skeletons with distinctive
postcranial morphologies have challenged this hypothesis. However,
ecomorphological analyses of these new postcrania have focused on a single
taxon, a limited region of the skeleton, or have been largely qualitative.
For more comprehensive locomotor inference in Mesozoic mammals, we applied
multivariate analyses to a morphometric data set of extant small-bodied
mammals. We used 30 osteological indices derived from linear measurements
of appendicular skeletons of 107 extant taxa that sample 15 orders and
eight locomotor modes. Canonical variate analyses show that extant
small-bodied mammals of different locomotor modes have detectable and
predictable morphologies. The resulting morphospace occupation reveals a
morphofunctional continuum that extends from terrestrial to scansorial,
arboreal, and gliding modes, reflecting an increasingly slender
postcranial skeleton with longer limb output levers adapted for speed and
agility, and extends from terrestrial to semiaquatic/semifossorial and
fossorial modes, reflecting an increasingly robust postcranial skeleton
with shorter limb output levers adapted for powerful, propulsive strokes.
We used this morphometric data set to predict locomotor mode in ten
Mesozoic mammals within the Docodonta, Multituberculata, Eutriconodonta,
“Symmetrodonta,” and Eutheria. Our results indicate that these fossil taxa
represent five of eight locomotor modes used to classify extant taxa in
this study, in some cases confirming and in other cases differing from
prior ecomorphological assessments. Together with previous locomotor
inferences of 19 additional taxa, these results show that by the Late
Jurassic mammals had diversified into all but the saltatorial and active
flight locomotor modes, and that this diversification was greatest in the
Eutriconodonta and Multituberculata, although sampling of postcranial
skeletons remains uneven across taxa and through time.

中生代哺乳动物的生态形态多样性推测受限于同期脊椎动物施加的选择压力。因此，长期以来中生代哺乳动物被视为泛化、陆生、小型躯体的类群，其运动特化程度有限。近年来发现的具有独特颅后骨骼形态的中生代哺乳动物化石骨架，对这一假说提出了挑战。然而，针对这些新颅后骨骼的生态形态学分析多聚焦于单一分类群、骨骼的有限区域，或多为定性研究。为更全面地推断中生代哺乳动物的运动方式，我们对现生小型躯体哺乳动物的形态测量数据集进行了多变量分析。我们采用了30项骨骼学指标，这些指标源于107种现生分类群附肢骨骼的线性测量，涵盖15个目和8种运动方式。典型变量分析显示，不同运动方式的现生小型躯体哺乳动物具有可检测且可预测的形态特征。所得的形态空间占据结果揭示了一条形态功能连续体：从陆生模式延伸至攀缘、树栖及滑翔模式，体现为颅后骨骼逐渐纤细，肢体输出杠杆更长，以适应速度与敏捷性；同时从陆生模式延伸至半水生/半穴居及穴居模式，体现为颅后骨骼逐渐粗壮，肢体输出杠杆更短，以适应强力推进动作。我们利用该形态测量数据集，预测了 docodonta目（Docodonta）、多瘤齿兽目（Multituberculata）、真三尖齿兽目（Eutriconodonta）、对称齿兽类（"Symmetrodonta"）及真兽亚纲（Eutheria）中的十种中生代哺乳动物的运动方式。结果表明，这些化石分类群涵盖了本研究中用于划分现生类群的8种运动方式中的5种，部分结果与先前的生态形态学评估一致，部分则存在差异。结合对另外19个分类群的先前运动方式推断，这些结果显示，至晚侏罗世，哺乳动物已分化出除跳跃（saltatorial）和主动飞行外的所有运动方式，且真三尖齿兽目和多瘤齿兽目的分化程度最高，尽管颅后骨骼的采样在不同分类群及时间尺度上仍不均匀。