贵州寒武纪杷榔组Changaspis elongata Chien,1961个体发育研究及意义

根据采自贵州剑河辣子寨杷榔组的张氏虫Changaspis 296块标本,采用传统形态测量方法,对头部及躯干特征进行度量;结合散点图、简化主轴回归分析及线性拟合对比分析后,确认这些标本均为长形张氏虫Chang-aspis elongata的标本,厘定出从分节6期至成虫期共计12个连续个体发育序列,揭示其形态变化特点。从分节6期至10期,背壳长、头鞍长、头盖长和宽的增长幅度相对小;随着体节的增多,头盖长度与背壳长度的比值从50%减少至34%;随着头鞍长度的增长,头鞍前部及后部宽均呈线性关系的连续增长趋势;个体发育序列确认该种成虫期有17节胸节,不同以往认为的16节胸节。对比分析及线性拟合的数据比较论证,确认原为C.micropyge和C.placenta 2个种的特征应为C.elongata在个体发育变化中的种内差异,确认先前命名的这2种应为C.elongata的晚出同义名。

ONTOGENY FOR CHANGASPISELONGATA CHIEN,1961FROM THE CAMBRIAN BALANG FORMATION OF GUIZHOU PROVINCE AND ITS IMPLICATION

Based on 296 specimens of Changaspis elongata from the Lazizhai section of the Cambrian Balang Formation in Jianhe County, Guizhou Province, the traditional morphometric method was used to measure the features of the cranidium and trunk. Combining the scatter plots, Reduced Major Axis regression and linear fitting, it was confirmed that these specimens are ascribed to Changaspis elongata, and a total of 12 continuous ontogenetic stages from meraspid degree 6 to holaspid stage are determined, revealing the morphological characteristics of the ontogeny. The growth range of the dorsal skeleton length, glabellar length, cranidial length and width are relatively small from the meraspid degrees 6 to 10. The proportion of the cranidial length to length of dorsal skeleton gradually decreased from 50% to 34% with the growth of the segments. With the increase of the glabellar length, the anterior and posterior width of the glabella show the linear growth trend. The ontogenetic sequence confirmed that the holaspid stage of C. elongata has 17 thoracic segments, which was different from the previous 16 segments. The scatter plot and linear fit suggested that the original specimens of C. micropyge and C. placenta should be intraspecific variation of the ontogeny of C. elongata, reconfirming that the two species should be synonyms of C. elongata.