In situ spores from Lower Gondwana ferns- their morphology and variation

Abstract

The paper deals with the study of morphology and variation of in situ spores of four fern species of the Raniganj Stage, Lower Gondwana, viz., Dizeugotheca phegopteroides (Feistmantel) Maithy, Dichotomopteris lindleyii (Royle) Maithy, Dichotomopteris major (Feistmantel) Maithy and Neomariopteris hughesii (Zeiller) Maithy. The variation exhibited by the spores in their size, shape, tetrad-mark and sculpture has been biometrically assessed for a better definition of the species. Study of the spores by SEM has further helped in elucidating their morphological characters.

Dizeugotheca phegopteroides has trilete to monolete, conate spores comparable with Apiculatisporis, Punctatosporites and Ghoshiasporites. Dichotomopteris lindleyii is now shown to have microbaculate sculpture comparable with Cyclobaculisporites. Dichotomopteris major and Neomariopteris hughesii possess closely similar spores characterized by a heterogeneous mixture of cones, spines, and bacula and the spores are referable to dispersed spore genera like Lophotriletes, Acanthotriletes and rarely Horriditriletes. The strong overlap between the spore characters of the two species is biometrically evaluated. The evidence indicates that there can hardly be any correlation between megafossil and miospore taxa found in a dispersed state. The quality of sculpture in the Lower Gondwana spores is by and large distinct from that of the north hemispheric (Carboniferous) ferns.