ABSTRACT

The lower jaw of the holotype of Adalatherium hui, from the Late Cretaceous of Madagascar, is the most complete yet known for a gondwanatherian mammal. It reveals for the first time the morphology of the character-rich ascending ramus of the dentary in a gondwanatherian. Each half of the lower jaw is composed of only one bone, the dentary, which is short and deep and houses only five teeth: an enlarged, procumbent incisor and four postcanine teeth. In comparable parts of its anatomy, the dentary of Adalatherium is strikingly similar to that of Sudamerica but differs slightly from that of Galulatherium (conformation anterior to first postcanine, mental foramen position), the only two other gondwanatherians represented by complete horizontal rami. Among other Mesozoic mammaliaform taxa, the dentary of Adalatherium is most similar to those of the largely Laurasian group Multituberculata, most notably in absence of postdentary trough and Meckelian sulcus; presence of short, deep dentary with sizable diastema and articulating with squamosal via mediolaterally narrow condyle that continues onto posterior surface (i.e., no distinct peduncle); possession of much reduced dentition; absence of angular process; possession of large pterygoid fossa and pterygoid shelf, ventral surface of which is flat; absence of coronoid bone; and possession of unfused mandibular symphysis. Most of these features are clearly derived and stand in stark contrast to the much more plesiomorphic morphology exhibited by the lower jaw of the haramiyaviid Haramiyavia. The lower jaws of euharamiyidans, although derived in their own right, are also relatively plesiomorphic.

摘要

来自马达加斯加晚白垩世的阿达拉图姆·惠（Adalatherium hui）整型的下颚，是最完整的，但以冈瓦纳特哺乳动物为人所知。它首次揭示了冈瓦纳特人牙齿中字符丰富的升支支齿的形态。下颌的每一半仅由一根短而深的牙齿组成，而牙齿仅容纳五颗牙齿：一个扩大的前牙和四个犬齿。在它的解剖学的可比的部分，的齿骨Adalatherium是惊人地相似的Sudamerica但稍有不同从的Galulatherium（第一个犬的前部形态，精神孔位置），另外两个仅以完全水平拉米为代表的冈瓦纳特人。在其他中生哺乳动物类群中，Adalatherium的牙齿与大部分劳拉斯族的Multituberculata最相似，最显着的是没有齿后槽和Meckelian沟；短而深的牙本质，具有较大的扩张性，并通过持续延伸到后表面的中外侧狭窄con突与鳞状部衔接（即没有明显的花序梗）；拥有大大减少的牙列；没有角度过程; 拥有大型翼节窝和翼节架，腹面平坦；没有冠状骨; 并拥有未融合的下颌骨。这些特征中的大多数都清晰可见，与haramiyaviid Haramiyavia的下颌表现出的更加多形的形态形成鲜明对比。euharamiyidans的下颌虽然是靠自身获得的，但也相对呈类形。