Abstract:
Based on large amount of specimens and data gathered from literature, a detailed morphometric analysis has been conducted to study the ontogeny and evolution of robustoschwagerinids, a group of Permian Schwagerinidae including 31 species originally put under the name of Robustoschwagerina M.-Maclay, 1956 (Table Ⅰ).For all the species studied, the rate of shape change has been calculated and compared for each volution, which was defined as the ratio of the non-overlap area between two adjacent volutions to the area of preceding volution (Fig. 1). Three different types of shape change, labeled as A, B and C respectively in the inset of Figure 1, have been recognized in the ontogenetic process of robustoschwagerinids.
