Synapsids are unique in having developed multirooted teeth and complex occlusions. These innovations evolved in at least two lineages of mammaliamorphs (Tritylodontidae and Mammaliaformes). Triassic fossils demonstrate that close to the origins of mammals, mammaliaform precursors were “experimenting” with tooth structure and function, resulting in novel patterns of occlusion. One of the most surprising examples of such adaptations is present in the haramiyidan clade, which differed from contemporary mammaliaforms in having two rows of cusps on molariform crowns adapted to omnivorous/herbivorous feeding. However, the origin of the multicusped tooth pattern present in haramiyidans has remained enigmatic. Here we describe the earliest-known mandibular fossil of a mammaliaform with double molariform roots and a crown with two rows of cusps from the Late Triassic of Greenland. The crown morphology is intermediate between that of morganucodontans and haramiyidans and suggests the derivation of the multicusped molariforms of haramiyidans from the triconodont molar pattern seen in morganucodontids. Although it is remarkably well documented in the fossil record, the significance of tooth root division in mammaliaforms remains enigmatic. The results of our biomechanical analyses (finite element analysis [FEA]) indicate that teeth with two roots can better withstand stronger mechanical stresses like those resulting from tooth occlusion, than teeth with a single root.

突触是独特的，具有发达的多根牙齿和复杂的咬合。这些创新至少在哺乳动物形态的两个世系（Tritylodontidae和Mammaliaformes）中得到了发展。三叠纪化石表明，接近哺乳动物的起源，哺乳动物形式的前体正在“实验”牙齿的结构和功能，从而形成了新颖的咬合模式。这种适应性的最令人惊讶的例子之一是haramiyidan进化枝，它与当代的哺乳动物形式不同，在臼齿冠上有两排尖齿，适合杂食/食性喂养。然而，存在于haramiyidans中的多尖牙模式的起源仍然是个谜。在这里，我们描述了最早的哺乳动物下颌骨化石，它具有双臼齿状根和一个冠，冠上有两行尖齿，出自格陵兰晚期三叠纪。冠状形态介于摩根巨齿兽类和原核生物之间，这表明原发性多齿尖齿的象形虫是从摩根巨齿兽类中的三尖齿磨牙模式衍生而来的。尽管它在化石记录中有很好的记录，但在哺乳动物中齿根分裂的重要性仍然是个谜。我们的生物力学分析结果（有限元分析[FEA]）表明，具有两个根部的牙齿比具有单个根部的牙齿能够更好地承受更强的机械应力，例如牙齿咬合所产生的应力。冠状形态介于摩根巨齿兽类和原核生物之间，这表明原发性多齿尖齿的象形虫是从摩根巨齿兽类中的三尖齿磨牙模式衍生而来的。尽管它在化石记录中有很好的记录，但在哺乳动物中齿根分裂的重要性仍然是个谜。我们的生物力学分析结果（有限元分析[FEA]）表明，具有两个根部的牙齿比具有单个根部的牙齿能够更好地承受更强的机械应力，例如牙齿咬合所产生的应力。冠状形态介于摩根巨齿兽类和原核生物之间，这表明原发性多齿尖齿的象形虫是从摩根巨齿兽类中的三尖齿磨牙模式衍生而来的。尽管它在化石记录中有很好的记录，但在哺乳动物中齿根分裂的重要性仍然是个谜。我们的生物力学分析结果（有限元分析[FEA]）表明，具有两个根部的牙齿比具有单个根部的牙齿能够更好地承受更强的机械应力，例如牙齿咬合所产生的应力。哺乳动物形态中牙根分裂的重要性仍然是个谜。我们的生物力学分析结果（有限元分析[FEA]）表明，具有两个根部的牙齿比具有单个根部的牙齿能够更好地承受更强的机械应力，例如牙齿咬合所产生的应力。哺乳动物形态中牙根分裂的重要性仍然是个谜。我们的生物力学分析结果（有限元分析[FEA]）表明，具有两个根部的牙齿比具有单个根部的牙齿能够更好地承受更强的机械应力，例如牙齿咬合所产生的应力。