Archosauria (birds, crocodilians and their extinct relatives) form a major part of terrestrial ecosystems today, with over 10 000 living species, and came to dominate the land for most of the Mesozoic (over 150 Myr) after radiating following the Permian–Triassic extinction. The archosaur skull has been essential to this diversification, itself diversified into myriad forms. The archosauriform Euparkeria capensis from the Middle Triassic (Anisian) of South Africa has been of great interest since its initial description in 1913, because its anatomy shed light on the origins and early evolution of crown Archosauria and potentially approached that of the archosaur common ancestor. Euparkeria has been widely used as an outgroup in phylogenetic analyses and when investigating patterns of trait evolution among archosaurs. Although described monographically in 1965, subsequent years have seen great advances in the understanding of early archosaurs and in imaging techniques. Here, the cranium and mandible of Euparkeria are fully redescribed and documented using all fossil material and computed tomographic data. Details previously unclear are fully described, including vomerine dentition, the epiptergoid, number of premaxillary teeth and palatal arrangement. A new diagnosis and cranial and braincase reconstruction is provided, and an anatomical network analysis is performed on the skull of Euparkeria and compared with other amniotes. The modular composition of the cranium suggests a flexible skull well adapted to feeding on agile food, but with a clear tendency towards more carnivorous behaviour, placing the taxon at the interface between ancestral diapsid and crown archosaur ecomorphology, corresponding to increases in brain size, visual sensitivity, upright locomotion and metabolism around this point in archosauriform evolution. The skull of Euparkeria epitomizes a major evolutionary transition, and places crown archosaur morphology in an evolutionary context.

主龙类（鸟类、鳄鱼及其已灭绝的近亲）构成了当今陆地生态系统的重要组成部分，拥有超过 10 000 种现存物种，并在二叠纪-三叠纪灭绝后辐射到中生代的大部分地区（超过 150 密尔），并开始在陆地上占据主导地位。祖龙头骨对于这种多样化至关重要，它本身也多样化为多种形式。南非中三叠世（阿尼西亚期）的古龙形Euparkeria capensis自 1913 年首次描述以来一直引起人们极大的兴趣，因为它的解剖结构揭示了冠龙类的起源和早期进化，并可能接近古龙类共同祖先。Euparkeria已被广泛用作系统发育分析和研究祖龙性状进化模式的外类群。尽管在 1965 年进行了专题描述，但随后几年人们对早期祖龙的理解和成像技术取得了巨大进步。在这里，使用所有化石材料和计算机断层扫描数据完全重新描述和记录了Euparkeria的头骨和下颌骨。以前不清楚的细节得到了充分描述，包括犁骨齿列、上翼骨、前上颌牙齿的数量和腭排列。提供了新的诊断以及颅骨和脑壳重建，并对Euparkeria的头骨进行了解剖网络分析，并与其他羊膜动物进行了比较。颅骨的模块化组成表明，其灵活的头骨非常适合以敏捷的食物为食，但具有明显的肉食行为倾向，将分类单元置于祖先双孔动物和冠主龙生态形态之间的界面，这与大脑尺寸、视觉能力的增加相对应。古龙类进化中围绕这一点的敏感性、直立运动和新陈代谢。Euparkeria的头骨体现了一次重大的进化转变，并将冠龙的形态置于进化背景中。