Eospalax, of the only two extant genera within the Myospalacinae, has a high species richness. Each species is distinguished by unique cranial and dental morphologies, as well as variations in temporal and spatial distribution. Consequently, Eospalax serves as a reliable indicator for the biochronologic and paleoenvironmental studies of the Quaternary of East Asia. A recent discovery of a complete fossil skull in a conglomerate deposit, a part of the Lower Pleistocene Sanmen Formation, near Jianyucha Town, Zichang County, northern Shaanxi Province, has been subjected to a detailed analysis. The specimens were identified as Eospalax simplicidens, an extinct species of Eospalax, based on dental morphology. The recent discovery of E. simplicidens in Jianyucha offers significant insights into the species’ cranial morphology and contributes to a more comprehensive understanding of its geographical distribution. The distinctive feature of the posterodorsal location of the external acoustic meatus indicates either a plesiomorphy or an evolutionary convergence among E. simplicidens, African root rats (Tachyoryctes), and bamboo rats (Rhizomyini). A skull (IVPP V5398.1) and four upper jaws (V5398.2) from Gongwangling in Lantian, Shaanxi, previously identified as Myospalax fontanieri, is transferred to the species E. lingtaiensis. A skull (IVPP RV35055) from Jingou, Xin’an, Henan, previously identified as E. simplicidens, is transferred to the species E. youngianus. In this study, body mass estimates are made for extinct Eospalax. Both E. lingtaiensis and E. simplicidens are small-sized zokors, with an estimated body mass of less than or approximately 300 g, respectively.

始鼢鼠属(Eospalax)是鼢鼠亚科两个仅存的现生属中的一员，其种类丰富。该属的每个种都具有较易区分的颅牙形态特征和不同的时空分布。因此，始鼢鼠属可以作为东亚第四纪研究中生物年代和古环境判断的代表性类群。最近在陕西省北部的子长县涧峪岔镇发现了始鼢鼠属的一件头骨及其关联的下颌化石，这些化石产自下更新统三门组的下部砾岩层。对此件标本进行了详细研究，根据牙齿形态将之归入已绝灭的简齿始鼢鼠(E. simplicidens)中。涧峪岔简齿始鼢鼠的发现不仅为该种的头骨形态特征提供了补充，还扩展了其地理分布。研究发现，简齿始鼢鼠的外耳道位置明显比其他鼢鼠种类更靠后背侧，更类似于非洲鼹形鼠(Tachyoryctes)和竹鼠族(Rhizomyini), 这表明简齿始鼢鼠与后两者之间在颅骨形态上可能存在保留祖征(plesiomorphy)或趋同演化的现象。此外，陕西蓝田公王岭的一件头骨(IVPP V5398.1)和四件上颌(V5398.2)之前被归入东方鼢鼠Myospalax fontanieri, 河南新安金沟的一件头骨(IVPP RV35055)之前被归入简齿始鼢鼠，它们分别被重新归入灵台始鼢鼠E. lingtaiensis和杨氏始鼢鼠E. youngianus。还尝试对始鼢鼠各化石种的体重进行了估算，结果显示，灵台始鼢鼠和简齿始鼢鼠都是小型鼢鼠，体重估算值分别为小于300 g和接近300 g。