豪猪化石在临夏盆地的新发现

New Hystrix(Hystricidae,Rodentia)from the Neogene of Linxia Basin,Gansu,China

近年来,在甘肃临夏盆地又发现了4件豪猪类的头骨化石,它们属于Hystrix的一新种,被命名为短吻豪猪(Hystrix brevirostra)。该种的主要特征是,个体大,头骨相对较低宽,吻部和齿隙较短,较短的鼻骨的后缘为向后凸的弧形,其后端约与泪骨相对。下颌骨的下齿隙较短,凹入较深。颊齿齿冠较H.gansuensis者稍低,较H.lufengensis者稍高。DP4的舌侧沟不与颊侧褶I相连,P4的舌侧沟伸向中脊,不与颊侧褶II相连。邓涛等(2011)曾将产于对康的一件豪猪头骨化石鉴定为H.gansuensis。现研究表明,他们描述的标本(HMV 2003)应属于不同于H.gansuensis的新种:H.brevirostra。将H.brevirostra(新种)的幼年的头骨与成年的头骨比较后发现,豪猪头骨的一些特征随着年龄的增长而有所变化:硬腭和鼻骨后缘的相对位置均随着年龄的增长而逐渐后移,两上颊齿列在幼年彼此稍向后靠近,但在成年则彼此平行等。关于百花村(LX 200205)和山城(LX 200041)两地点产豪猪化石层位的时代,根据共生的哺乳动物群分析,其时代为晚中新世晚期。产于我国新近纪的豪猪化石目前仅已知3种(H.gansuensis,H.lufengensis和H.brevirostra)。新种H.brevirostra可能比H.lufengensis稍进步,但较H.gansuensis稍原始。由于H.brevirostra的吻部较H.gansuensis和H.lufengensis者都短,它可能代表不同于该两种的另一进化支系。

Four well preserved skulls of Hystrix recently collected from Linxia Basin were studied and a new species,H.brevirostra sp.nov,was established for them.The new species is characterized by its larger size,relatively low and wide skull with short rostrum and diastema,slightly posteriorly convex posterior border of relatively short nasal roughly aligning with lacrimal,shorter and deeply curved mandibular diastema,and relatively low-crowned cheek teeth.It is intermediate between H.lufengensis and H.gansuensis in evolutionary level,existing in Late Miocene‒Pliocene.While it might represent a lineage separated from the above two species.Ontogenetic variation in skull morphology and direction of cheek tooth rows of the new species was also discussed.