The Genus Dicroidium from the Triassic of Nidpur, Madhya Pradesh, India

Abstract

Three new species of Dicroidium are desc1'ibed here from the Triassic of Nidpur, Sidhi District, Madhya Pradesh. Externally these three species are very similar to each other except that in D. nidpurensis and D. papillosum the venation is odontopteroid type, whereas, in D. gopadensis it is alethopteroid type. In the cuticular structure these species differ from each other main Iv in the presence or absence of papillae. In D. nidpurensis cell surface is smooth but in D. papillosum and D. gopadensis surface wall is usually papillate. In D. papillosum, subsidiary cells may be unspecialized or papillate, whereas, in D. gopadensis they are usually papillate.

Reappraisal of the genus Dicroidium Gothan from the Triassic sediments of India

“…In gross features and venation pattern the two sets of specimens are indistinguishable. According to Bose and Srivastava (1971) their cuticular features are also similar, except for the presence of papillae over epidermal cells in specimens of Dicroidium papillosum and their absence in specimens of Dicroidium nidpurensis. This papillate or non-papillate epidermal cells had been the basis of separation of Dicroidium papillosum and Dicroidium nidpurensis by the authors of the two species.…”

“…A specimen from Kamthi sequence depicts the proximal forking of primary rachis (Pl.1.7). Bose & Srivastava, 1971 (Pl. 2.1-2; Fig.…”

“…Remarks-Compressions of Dicroidium nidpurensis and Dicroidium papillosum were described from the Nidpur beds by Bose and Srivastava (1971). In gross features and venation pattern the two sets of specimens are indistinguishable.…”

“…Therefore, institution of a separate species based only on absence of papillae over epidermal cells is in no way justified. Moreover, in specimens of Dicroidium nidpurensis, as described by Bose and Srivastava (1971), the surface of epidermal cells in all probabilities represents illpreserved papillae. In some specimens figured by Bose and Srivastava (1971) such ill-preserved papillae are visible.…”

“…from the Panchet Formation of Auranga Coalfield. Bose and Srivastava (1971) described three new species of the genus, viz. D. nidpurensis, D. papillosum and D. gopadensis based on compression specimens from the Nidpur beds of South Rewa Gondwana Basin.…”