Oviraptorosaurs are among the most diverse and best-known extinct theropod groups. Their bizarre anatomy and their social and reproductive behaviour are now well understood. Among the oviraptorid subclade, the two-fingered Oksoko avarsan is particularly well-represented. It is known from several exquisite skeletons, preserving not only the entire skeleton, but multiple stages through ontogeny, providing an exemplar for understanding the anatomy of oviraptorids and the changes that their skeletons experienced over their lifetimes. Here I comprehensively describe the osteology of Oksoko avarsan and comment on its ontogenetic variation. Excellent preservation of the specimens provides unparalleled detail into the anatomy of an oviraptorid, providing valuable context for interpreting other oviraptorosaurs. Several changes are observed to occur through ontogeny relating to robustness of the bones and proportions of the skeleton, but there is little evidence suggesting that discrete features like the cranial crest arose late in ontogeny. Instead, early development of the cranial crest in oviraptorids, and its internal connection with the nasal passages and other pneumatic spaces, argue in favour of a role in vocalization, perhaps alongside sexual display. Detailed anatomical and ontogenetic data, like those provided by known specimens of Oksoko avarsan, are necessary to help to underpin ongoing research into the palaeobiology and macroevolution of Oviraptorosauria.

中文翻译：

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两指偷蛋龙科 Oksoko avarsan 的骨学（兽脚亚目：偷蛋龙亚目）

偷蛋龙是最多样化和最著名的已灭绝兽脚亚目类群之一。它们奇特的解剖结构以及它们的社会和繁殖行为现在已经被人们所熟知。在偷蛋龙科中，两指的奥克索科阿瓦桑（Oksoko avarsan）尤其具有代表性。人们从几具精美的骨骼中得知，它们不仅保存了整个骨骼，而且还保存了个体发育的多个阶段，为理解偷蛋龙的解剖结构及其骨骼在一生中经历的变化提供了一个范例。在这里我全面描述了Oksoko avarsan的骨学并对其个体发生变异进行了评论。标本的完好保存为偷蛋龙科的解剖提供了无与伦比的细节，为解释其他偷蛋龙类提供了宝贵的背景。观察到在个体发育过程中发生了与骨骼的坚固性和骨骼比例相关的一些变化，但几乎没有证据表明像颅嵴这样的离散特征在个体发育后期出现。相反，窃蛋龙类颅嵴的早期发育，及其与鼻腔和其他气动空间的内部联系，支持发声中的作用，也许与性展示同时存在。详细的解剖学和个体发育数据，如已知的奥克索科阿瓦尔桑标本提供的数据，对于帮助支持正在进行的偷蛋龙类古生物学和宏观进化研究是必要的。