We here describe a new Early Cretaceous (early Albian) eutherian mammal, Sasayamamylos kawaii gen. et sp. nov., from the ‘Lower Formation’ of the Sasayama Group, Hyogo Prefecture, Japan. Sasayamamylos kawaii is characterized by a robust dentary, a distinct angle on the ventral margin of the dentary at the posterior end of the mandibular symphysis, a lower dental formula of 3–4 : 1 : 4 : 3, a robust lower canine, a non-molariform lower ultimate premolar, and a secondarily reduced entoconid on the molars. To date, S. kawaii is the earliest known eutherian mammal possessing only four premolars, which demonstrates that the reduction in the premolar count in eutherians started in the late Early Cretaceous. The occurrence of S. kawaii implies that the relatively rapid diversification of eutherians in the mid-Cretaceous had already started by the early Albian.
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机译：我们在这里描述了一种新的早白垩世（早期阿尔比亚）的以太哺乳动物，Sasayamamylos kawaii gen。等。 11月，来自日本兵库县Sasayama集团的“下层组”。 Sasayamamylos kawaii的特征是坚固的牙齿，在下颌骨联合的后端，牙齿的腹缘上有一个明显的角度，较低的牙齿配方为3–4：1：4：3，坚固的下犬齿， -molariform降低最终的前磨牙，然后在臼齿上再次还原对映体。迄今为止，卡哇伊链球菌是已知的仅具有四个前磨牙的真人生物，这表明，从白垩纪晚期开始，真人生物的前磨牙数量减少。 S. kawaii的出现意味着白垩纪中期的以太坊人相对较快的多样化已经在早期的Albian时代就开始了。
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