摘要
A new species,Helicoprion jingmenense sp. nov.,from the Lower Permian Qixia Formation of Hubei Province,China,is described based on a nearly complete symphyseal tooth spiral preserved as part and counterpart. The specimen is a large elliptical symphyseal tooth spiral with 41/3 volutions,with cutting blade being relatively wide,and its width being greater than the height after 31/2 volution,middle portion being higher than the cutting blade,narrowed base being short. There is a distinct space not covered by enameloid in two adjacent tooth crowns in the outermost two volutions; the height of the compound root is moderate,and the ventral groove is about 1/10 of the same tooth crown. In com-parison with other known Helicoprion species of the world,the new species resembles H. ferrieri and H. bessonowi. However,it can be easily distinguished from H. ferrieri by the wider cutting blade,the shorter narrowed base and lower compound root,and also from H. bessonowi by its more narrowed compound root and less than 39 tooth crowns per volution. Helicoprion jingmenense sp. nov. is obvi-ously different from helicoprionid species previously found in China in general shape,size and his-tology. However,it is very difficult to identify their relationships because of the fragmentary nature of holotypes of the latter. Because the new specimen is the first record of Helicoprion and the most com-plete fossil dentition of helicoprionids from China,the new species is of significance for biostratigra-phy and paleobiogeography.
A new species, Helicoprion jingmenense sp. nov., from the Lower Permian Qixia Formation of Hubei Province, China, is described based on a nearly complete symphyseal tooth spiral preserved as part and counterpart. The specimen is a large elliptical symphyseal tooth spiral with 4^1/3 volutions, with cutting blade being relatively wide, and its width being greater than the height after 3^1/2 volution, middle portion being higher than the cutting blade, narrowed base being short. There is a distinct space not covered by enameloid in two adjacent tooth crowns in the outermost two volutions; the height of the compound root is moderate, and the ventral groove is about 1/10 of the same tooth crown. In com- parison with other known Helicoprion species of the world, the new species resembles H. ferrieriand H. bessonowi. However, it can be easily distinguished from H. ferrieri by the wider cutting blade, the shorter narrowed base and lower compound root, and also from H. bessonowi by its more narrowed compound root and less than 39 tooth crowns per volution. Helicoprion jingmenense sp. nov. is obviously different from helicoprionid species previously found in China in general shape, size and histology. However, it is very difficult to identify their relationships because of the fragmentary nature of holotypes of the latter. Because the new specimen is the first record of Helicoprion and the most complete fossil dentition of helicoprionids from China, the new species is of significance for biostratigraphy and paleobiogeography.
基金
Supported by Program of Excellent Young Scientists of the Ministry of Land and Resources and Geological Survey Project (Grant No. 1212010611603)
