记广西田东却林缅甸先炭兽的新材料

NEW MATERIAL OF ANTHRACOKERYX BRIMANICUS FROM GUANGXI,CHINA

记述了产自广西田东县却林那读组中一残破的缅甸先炭兽 (Anthracokeryxbirmanicus)头骨。通过对化石的描述 ,对该种特征进行了补充和分析 ,并认为其终生生长的上犬齿可能是用来作为争夺领域和配偶的武器。终生生长的上犬齿的发现 ,证明炭兽类具有性双形。将那读动物群和缅甸邦唐动物群进行对比 。

A new specimen of Anthracokeryx brimanicus with a complete upper dentition,collected from the Nadu Formation of Quelin,Guangxi in 1990,is described in this paper. Left C,P1~M3,right I2~C,P3~M3 are preserved on the upper jaw. Examination of the new specimen resulted in the emend of the species diagnosis:the interval beween the two incisors is relatively large. The upper canine is large (probably only in adult male),curved outwards and backwards. It extends far back to the posterior end of maxilla,and has no enclosed root,which suggests the canine is ever growth. The dentition formula of the upper jaw is 4·3. The outer cusp of P4 is crescentic and the inner cusp is conical. The molar has a well marked parastyle,a moderate mesostyle and a weak metastyle. Cingulum is moderate. The shape of the canine of the Anthracokeryx brimanicus,similar to that of both the male muntjac and the male musk,indicates that the canine was used as a weapon to fight for mate and territory. The finding of upper canine implies that Anthracokeryx brimanicus is sexual dimorphic. Bicuspid P4 of Anthracokeryx birmanicus (crescentic outer cusp and conical inner cusp) differs from that of A. kwangsiensis,A. gungkangensis and A. dawsoni. The outer cusp of P4 of A. kwangsiensis is conical and the inner cusp is flat conical;the anterior cingulum and the posterior cingulum are well developed,but absent at the anterior part of the outer cusp and the external of the inner cusp. In A. gungkangensis, the outer cusp is conical and the inner cusp is crescentic;cingulum is well developed. The outer cusp and the inner cups of A. dawsoni are all conical. The age of the Nadu Formation was considered to be Late Eocene. Comparison with Pondaung fauna of Burma suggests that the Nadu Fauna might partially be Middle Eocene in age.