广西博白新型盾皮鱼类骨片的发现

The Discovery of New Placoderm Bones in Bobai,Guangxi

记述广西博白中泥盆世两件盾皮鱼类躯甲（中背片？）化石，其骨片狭长，前缘被覆压，侧缘后部覆压两侧的骨片而侧缘前部无覆压区，中腹突与中腹坑发育，纹饰为分布均匀且不连续的瘤突。该骨片与已知盾皮鱼类的中背片或后中背片均不相同，代表一新的属种：狭背博白鱼（Ｂｏｂａｉｌｅｐｉｓａｎｇｕｓｔｉｄｏｒｓａｌｉｓｇｅｎ．ｅｔｓｐ．ｎｏｖ．），其分类位置尚难确定。新属中背片侧缘前部缺少覆压区是其最重要的特征。

Two new Middle Devonian placoderm bones probably referred to median dorsal plates,which excavated from Bobai, southeastern Guangxi, are systematic described. They differs from median dorsal plates of Arthrodira and Petalichthyida, and from posterior median dorsal plates of Antiarchi in the special shapes, and in particular in these overlaps absent along the anterior and middle divisions of lateral margins. The specimens must be a new placoderm genus and species Bobailepis angustidorsalis gen. et sp. nov., but the systematic position is not determined. The generic diagnosis can be concluded as follows: Median dorsal plate norrow and long, more than 40mm in length and 20 mm in maximum breadth. Anterior portion very norrow. Anterior margin strongly convex, and the posterior flat. Paired lateral corner of lateral margin obvious. further postenorly. The dorsal side rises into a broad ridge rostrocaudally. Long vertral cavity and process developed on the visceral side. Externally anterior margin is overlapped, and internally the posterior division of lateral margin is occupied by the overlop area for the laterally located bone. The overlap area absent alone the anterior and middle portions of lateral margin. Out surface ornamented with rounded, closely situated tubercles.