记内蒙古Juxia一新种

本文记述了在内蒙古沙拉木伦额尔登敖包地区第三系下渐新统乌兰戈楚组中发现的始巨犀的一个新种:寿氏始巨犀(Juxia shoui)。据其前臼齿及鼻切迹的位置等特点,这一新种当为始巨犀属中比较进步的一个成员,是包氏始巨犀和巨犀之间的过渡类型的犀类动物。

A NEW SPECIES OF JUXIA(PERISSODACTYLA),NEI MONGOL

Juxia sharamurenense was described by Chow and Chiu in 1964 based on a skull and almost skeleton collected from the Upper Eocene Sharamurun Formation at Ula Usu in Shara Murun region,Nei Mongol.Owing to their resemblances in dental morphology and nearly the same size,Juxia sharamurenense,Eotrigonias borissiaki(Beliajeva,1959),and Eotrigonias ergiliinensis (Gabunia & Dashzeveg,1974)should be the same species—Juxia borissiaki(see Lucas & al., 1981). The reasons referred Juxia to Forstercooperia(Radinsky,1967)are as follows:1)Juxia is 15% smaller than Forstercooperia totadentata;2)“the incisors of Juxia are approximately equal-sized(I~1 is slightly larger than the others)and are followed by a large stubby canine,as in Pappaceras(=Forstercooperia)confluens,unlike the condition in Indricotherium,in which I_1~1 are greatly enlarged and the posterior incisors and canines are atrophied or lost.” Up to now,Juxia is still considered to be a valid genus by later writers(Chow,Chang, & Ting 1974;Lucas,Schoch,& Manning,1981)because there are following differences between Juxia and Forstercooperia:1)premolars higher molariform;2)nasal incision retracted to p~3, and 3)I~1 slightly larger than the others. Juxia shoui sp.nov.(V8757)differs from Juxia borissiakiin:1)smaller in size;2)p~(2-4) width enlarged;3)P~4:more malariform than that of Juxia borissiaki(V8757);and 4)the diastema much shorter than that of Juxia borissiaki. The new species further confirms the validity of the generic status of Juxia.