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