Abstract Caenagnathids were oviraptorosaur theropods characterized by elongate hind limbs that are proposed as adaptations for either wading or enhanced cursoriality. A lack of well preserved pelvic material, however, has thus far prevented reconstruction of both the hind limb and girdle for verification of these hypotheses. Here we describe an abundance of new caenagnathid pelvic material from the Dinosaur Park Formation of Alberta, Canada. These new specimens reveal more of the anatomy of the pelvis and can be tentatively divided into three morphotypes of varying body size. Improved representation of the pelvis allows for identification of osteological correlates for caenagnathid pelvic musculature based on extant phylogenetic bracketing and direct observation of muscle attachment sites. This provides a foundation for future studies on theropod locomotion and highlights one pelvic muscle origin inconsistent with existing literature. Among the putative morphotypes, variation in correlates of pelvic muscles and proportions of pelvic bones may have had functional implications, based on patterns in extant birds. These results suggest that caenagnathids show adaptations more congruent with wading than increased cursoriality, but that morphology and function within the group varied more than previously appreciated.

中文翻译：

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新材料揭示了Caenagnathidae（兽脚亚目，偷蛋龙目）的盆腔形态

摘要 Caenagnathids 是窃蛋龙兽脚类恐龙，其特征是细长的后肢，被提议作为涉水或增强游走性的适应。然而，迄今为止，由于缺乏保存完好的骨盆材料，因此无法重建后肢和腰带以验证这些假设。在这里，我们描述了来自加拿大艾伯塔省恐龙公园地层的大量新的 caenagnathid 骨盆材料。这些新标本揭示了更多的骨盆解剖结构，可以初步分为三种不同体型的形态类型。骨盆的改进表示允许基于现存的系统发育括号和肌肉附着位点的直接观察来识别 caenagnathid 骨盆肌肉组织的骨学相关性。这为未来兽脚类动物运动的研究奠定了基础，并突出了与现有文献不一致的骨盆肌肉起源。在假定的形态类型中，基于现存鸟类的模式，骨盆肌肉相关物和骨盆骨比例的变化可能具有功能影响。这些结果表明，caenagnathids 表现出的适应与涉水更一致，而不是增加的游标，但该组内的形态和功能变化比以前认为的更大。