Didymoconidae is an enigmatic family of Asian Paleogene eutherian mammals, with its early diversity remaining poorly documented. Here, we report a new genus and species, Erlianoryctes mengi gen. et sp. nov., based on a fragmentary, partial juvenile skull and associated lower dentition recovered from the Arshanto Formation of the Erlian Basin, Nei Mongol, China. The new taxon is characterized by the combination of characters: P3 with a small metacone and prominent protocone; P4 submolariform, with the metacone incompletely separated from the paracone, and a distinct postcingulum present; M1–2 with a prominent postcingulum; and m1–2 with a relatively large and lingually positioned paraconid, and a tricuspid talonid in which the hypoconid, hypoconulid and entoconid are arranged in an arc. Morphological comparisons and phylogenetic analyses indicate that the new species represents a basal didymoconine, bridging Archaeoryctes-like ancestors and derived didymoconines. Additionally, the new specimen reveals a tooth eruption sequence virtually identical to that of later didymoconids, indicating that the tooth eruption pattern, except for the P2/p2, is probably conservative within the family. 

描述了内蒙古二连盆地阿山头组中发现的对锥兽科(Didymoconidae)一新属种：孟氏二连对锥兽(Erlianoryctes mengi gen. et sp. nov.)，标本为一亚成年个体破碎头骨的前部及部分不完整下臼齿。新属种的特征为：P3具有雏形的后尖和显著的原尖；P4次臼齿化，其后尖与前尖未完全分隔，后齿带发育；M1–2后齿带显著；m1–2下前尖较大且位于近舌侧，下跟座具下次尖、下次小尖和下内尖且呈弧形排列。形态对比和系统发育分析显示，该新属种为对锥兽亚科(Didymoconinae)一基干类型，填补了古对锥兽(Archaeoryctes)和更进步的对锥兽亚科属种间的演化空白。新材料揭示的牙齿替换序列与更进步的对锥兽类几乎一致，表明对锥兽科的牙齿替换模式(除P2/p2外)可能是保守的。