کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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4749733 | 1360612 | 2012 | 21 صفحه PDF | دانلود رایگان |
The genus Choffatia (Siemiradzki) is an important Callovian ammonite in Kutch biostratigraphy. Several species of the genus were described by the early workers who did not recognize intraspecific variability and sexual dimorphism in terms of the modern concepts. We have described here three dimorphic species based on material reposited in the Geological Survey of India, Kolkata as well as systematically collected additional specimens with precise stratigraphic information. These species are: Choffatia recuperoi ( Gemmellaro, 1873), Choffatia cobra ( Waagen, 1875), and Choffatia perdagata ( Waagen, 1875). The microconchs of the three species, described here for the first time, are lappeted whereas the macroconchs have a simple aperture. However, these species have similar shell morphologies and they intergrade in shell shape and sculpture; thus it is difficult to distinguish them qualitatively. Statistical analyses (both bivariate and multivariate) support that they are distinct species and there is a good correlation among the degree of involution, the degree of inflation, and the strength of ornamentation. C. cobra is the most evolute, depressed, and strongly ribbed whereas C. perdagata is the most involute, compressed, and weakly ribbed. C. recuperoi occupies the intermediate position. This interspecific diversity of Choffatia thus supports Buckman's Law of Covariation.
Journal: Palaeoworld - Volume 21, Issue 1, January 2012, Pages 29–49