Petrified araucarian remains from Sonajori, Rajmahal Basin, India

Abstract

Permineralized araucarian ovulate and pollen cones are described here for the first time in close association from Early Cretaceous intertrappean rocks of the Sonajori Locality in the Rajmahal Basin, Jharkhand. These cones were found associated with woods and leafy shoots bearing spirally arranged falcate to oblanceolate leaves. The leaf, in longitudinal section shows epidermis followed by parenchymatous mesophyll and transfusion tissue. Ovulate cones, elliptical-spherical in shape, with spirally attached bracts and ovuliferous scales bearing mostly one and rarely two ovules/seeds per cone scale complex. Cone scale complex is characterised by the presence of "circa" (ligular sulcus). In one specimen, cross-section shows close association of numerous pollen grains with the cone scale complex of the cone indicating the preservation of cone at pollination stage. In another specimen, cross-section shows cone scale with oblong inverted ovule/seed, ovule integument/seed testa with three distinct layers, nucellus free except at chalazal end, shrunken at micropylar region and the presence of an embryonic tissue shows a post fertilisation stage of cone preservation. Anatomical features of these cones indicate various stages of cone maturity. The microsporangiate cone elongated in shape, in tangential view shows microsporophylls as well as circular-oval sporangia in cross-section. Transverse-sections of cone shows a central axis surrounded by numerous elongated narrow sporangia in longitudinal section and rhomboidal tip of the microsporophyll. The microsporophyll shows only parenchymatous tissue in sectional view of distal part: dispersed circular alete pollen grains are found associated with ovulate/seed cone and sterile shoots. Morphological and anatomical features of all the Indian species of araucarian cone described earlier are also critically assessed.