Abstract:

An anterior part of skull was recently found near Xiayangwan in Guanghe County, Gansu Province, presumably from the Liushu Formation. The skull represents a new species of Pararhizomys, named as Pararhizomys parvulus. The new species is characterized by: small size, upper molars higher crowned and mesio-lingually hypsodont with sinus deeper than mesosinus; sinus and mesosinus in M3 being transverse and overlapping each other, but sinus longer than mesosinus on occlusal view. Based on shared apomorphies (lingually hypsodont upper molars and transverse sinus and mesosinus on M3 occulsal surface), P. parvulus and P. huaxiaensis are supposed to form a sister group. However, P. parvulus may be more derived than P. huaxiaensis as demonstrated by the more hypsodont molars and the deeper sinus in M3.

Key words: Linxia Basin, Gansu, Late Miocene, Liushu Formation, Pararhizomys, Tachyoryctoidinae

摘要：

西北大学的野外考察队于2018年5月在甘肃广河县下杨湾附近的柳树组岩层的地表采得一啮齿类头骨的前部。该头骨的基本形态符合副竹鼠(Pararhizomys)的属征,但个体要比该属现已知的种都小,可能代表副竹鼠类一新种,命名为小副竹鼠(Pararhizomys parvulus)。新种的主要特征是：个体很小;臼齿齿冠较高,上臼齿系前侧高冠和舌侧高冠;M1‒3的舌侧内凹垂向深于颊侧的中凹;M3冠面视显示内凹和中凹均横向延伸,彼此稍重叠,内凹宽于中凹。根据Pararhizomys的进化趋势,在副竹鼠已知的4个种中,P. parvulus与P. huaxiaensis共有上臼齿具舌侧高冠和M3具横向延伸的内凹和中凹的特点,两种可能组成姐妹组。根据其臼齿的齿冠更高和内凹垂向深度更深的特点判断,P. parvulus可能比Pararhizomys目前已知的种(包括P. huaxiaensis)都进步。

关键词: 甘肃临夏盆地, 晚中新世, 柳树组, 拟速掘鼠亚科,副竹鼠属