记宁夏石炭纪古鳕类一新属

本文描述了一件保存较为完整的和一件仅头部保存的小型古鳕类化石.这两件化石标本采自宁夏中卫市常乐镇上河沿村和下河沿村石炭纪纳缪尔期晚期土坡组顶部.这类古鳕类身体细长,鳞片不甚发育,部分有印痕保存.舌颌骨微前倾,从顶骨中间部位延伸到颌弓终端,上颌骨后缘向下凸起比向上凸起明显,鳃盖骨比下鳃盖骨略大,眼眶大,且位置靠前,奇鳍条分节分叉现象明显,歪尾型明显,尾鳍上叶缩短,逐步向小型歪尾型演变.总的说来这两件标本拥有更多的软骨硬鳞鱼类向全骨鱼类演化的特征,建议将其定位为古鳕目的一个新属,其科级分类单元的归属在拥有更多的化石资料后再行确定.

A New Genus of Palaeonisciformes from Carboniferous Strata in Ningxia

Two specimens were discovered at the top of Tupo Formation (Late Namurian, Carboniferous) in Zhongwei city, Ningxia Hui Autonomous Region. Their bodies are long and thin with few scales. The hyomandibular is slightly oblique and extends from the middle of the parietal to the end of bigonial arch. The maxillary is faint hilt-shaped. The opercular is as big as subopercular. The orbital is large and far forward. The median fin-rays are segmented and branched. The dorsal lobe of the tail becomes reduced to an abbreviated heterocercal tail. In general, the two specimens possess many more remarkable characteristics in the process of evolution from the chondrosteans to the holosteians. So a new genus is proposed to create in Palaeonisciformes for the two specimens, and more specimens are needed to help us find out which family should the new genus belong to.