THE PRELIMINARY STUDY ON THE ONTOGENY OF TSUNYIELLA LUNA FROM THE CAMBRIAN NIUTITANG FORMATION IN SONGLIN TOWN,ZUNYI COUNTY,GUIZHOU PROVINCE
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Abstract:
The ontogeny of Tsunyiella luna of the Cambrian Niutitang Formation, Zunyi, Guizhou Province is studied preliminarily using the geometric morphometric method. The result shows that the growth pattern of T. luna is allometric. And the ratio between the hinge-line length and shell length is decreasing with inverse proportional function during the ontogeny. The ventral margin is balanced growth. However, the molting stage is still not clear now. The ontogeny can be divided into three stages: early stage, middle stage and late stage. In the early stage, structure is from scratch, and the ratio of the height to length became larger as the shell become round. In the middle stage, the proportion of anterior node and dorsal margin ridge in the shell and the ratio of height to length gradually decreased, and the mid-dorsal area gradually increased on the contrary and the shell form gradually retral swing. In the late stage, the proportion of anterior node in the shell increased slightly, and the dorsal margin ridge decreased, and the mid-dorsal area is not obvious, and the ratio of height to length increased, and the shell form was more round. This ontogenetic study provides more information for further study on taxonomy and phylogeny of T. luna.
