Haramiyida was a successful clade of mammaliaforms, spanning the Late Triassic period to at least the Late Jurassic period, but their fossils are scant outside Eurasia and Cretaceous records are controversial1–4. Here we report, to our knowledge, the first cranium of a large haramiyidan from the basal Cretaceous of North America. This cranium possesses an amalgam of stem mammaliaform plesiomorphies and crown mammalian apomorphies. Moreover, it shows dental traits that are diagnostic of isolated teeth of supposed multituberculate affinities from the Cretaceous of Morocco, which have been assigned to the enigmatic ‘Hahnodontidae’. Exceptional preservation of this specimen also provides insights into the evolution of the ancestral mammalian brain. We demonstrate the haramiyidan affinities of Gondwanan hahnodontid teeth, removing them from multituberculates, and suggest that hahnodontid mammaliaforms had a much wider, possibly Pangaean distribution during the Jurassic–Cretaceous transition.An exceptionally preserved skull of Cifelliodon wahkarmoosuch sheds light on the evolution of the ancestral mammalian brain.

中文翻译：

---

晚期幸存的茎哺乳动物将北美洲最下层的白垩纪和冈瓦纳纪联系在一起

Haramiyida 是一个成功的哺乳动物进化枝，跨越了晚三叠纪到至少晚侏罗纪，但它们的化石在欧亚大陆之外很少，白垩纪的记录是有争议的1-4。据我们所知，我们在这里报告了来自北美白垩纪基底的大型 haramiyidan 的第一个头盖骨。这个头盖骨拥有干哺乳动物形态 plesiomorphies 和冠哺乳动物异形的混合物。此外，它显示的牙齿特征可以诊断出与摩洛哥白垩纪具有多瘤亲缘关系的孤立牙齿，这些牙齿已被归为神秘的“Hahnodontidae”。这个标本的特殊保存也提供了对祖先哺乳动物大脑进化的见解。我们展示了冈瓦纳河豚类牙齿的 haramiyidan 亲和力，