湘西北地区寒武纪黔东世掘头虫类三叶虫Duyunaspis及其种内变异

DUYUNASPIS ZHANG AND QIAN IN ZHOU ET AL.,1977(TRILOBITA) FROM THE BALANG FORMATION(CAMBRIAN,QIANDONGIAN) IN NORTHWESTERN HUNAN PROVINCE AND ITS INTRASPECIFIC VARIATIONS

湖南省湘西土家族苗族自治州花垣县排吾乡附近寒武系黔东统杷榔组中产有丰富的Duyunaspis材料。通过对Duyunaspis duyunensis种内形态变化的观察,认为该种存在较大的种内变异(如头鞍形状、鞍沟中部是否完全相连、胸节数目和尾后缘是否具缺刻等),同时表明以往描记的Duyunaspis songtaoensis,D.guzhangensis,D.briaris和D.laevigatus 4个种,都是根据种内变异或保存差异建立的,应是模式种D.duyunensis的晚出异名。此外,Duyunaspis的新材料还包括一个产于湘西北的新种Duyunaspis paiwuensis sp.nov.。

Duyunaspis duyunensis Zhang and Qian in Zhou et al. , 1977 and D. paiwuensis sp. nov. are described herein based on the specimens recently collected from the Balang Formation （Cambrian, Qiandongian） at Zila Village, Paiwu, Huayuan, NW Hunan. The abundant material, through all ontogenetic stages of the type species Duyunaspis duyunensis, shows wide intraspecific variation for the species in the glabellar shape, the connecting states of the pitted glabellar furrows, the number of thoracic segments and either absence or presence of an anterior indentation on the pygidial end etc. Four species referred previously to Duyunaspis but based on the intraspecific variations are regarded as junior synoniums of D. duyunensis. They are Duyunaspis songtaoensis Qian and Lin in Zhou et al. , 1977, D. guzhangensis Zhou in Zhou et al. , 1977, D. briaris Chien and Lin in Yin and Li, 1978, and D. laevigatus Qian and Lin in Zhang et al., 1980, of which D. briaris is the objective senior synonym of Duyunaspis obesis Qian and Lin in Zhang et al. , 1980. The study of intraspecific variation could ensure more correct identification on different species and is very important to the relevant study.