Unraveling the origins of the character complexes diagnosing major crown clades is one of the greatest challenges in evolutionary biology. These origination events tend to optimize along extraordinarily long stem lineages where the comparative biology of extant lineages is relatively weak in its heuristic power. Here we add to a growing paleontological literature on the evolutionary origins of the modern avi an brain by describing the endocranial casts of two oviraptorosaur dinosaurs, Citipati osmolskae and Khaan mckennai. These fossil data confirm the antiquity of several avian features, including the expanded cerebrum. They also extend our appreciation of both the inherent variability in the brain-skull relationship along the avian stem and the dynamic nature of these crown characters in the earliest history of their expression.

中文翻译：

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甲龙恐龙的颅内腔和禽脑的日益复杂的深厚历史。

揭示诊断主要冠部进化枝的性状复合体的起源是进化生物学的最大挑战之一。这些起源事件倾向于沿着非常长的茎谱系进行优化，而现存谱系的比较生物学在其启发式能力方面相对较弱。在这里，我们通过描述两种锯齿恐龙（Cipipati osmolskae和Khaan mckennai）的颅内模型，增加了有关现代人类大脑进化起源的古生物学文献。这些化石数据证实了几个禽类特征的古代，包括扩大的大脑。他们还扩展了我们对沿鸟类茎部的脑-头骨关系固有的变异性以及这些冠状字符在其最早表达历史中的动态特性的理解。