On three new species of Pteruchus THOMAS from the Triassic of Nidpur, M.P., India

摘要

The present paper contains an account of three new species of the corystosperm pollen organ Pteruchus from the Middle Triassic beds of Nidpur, M.P. India. The new species P glandulatus, P lobatus, and P truncatus differ from each other in the nature of central axis, disposition and length of the microsporophyll stalk, angle of divergence of the stalk from the central axis, lobing of head margin, number and shape of microsporangia per head and cuticular details. In all the species, the central axis has square outline in cross section and bears spirally arranged microsporophylls. In P glandulatus, the stalked microsporophylls appeared to arise in low spirals from nodal regions leaving wide, naked internodal ar-eas. The central axis also shows secretory body like structures. In P lobatus, the microsporophylls are closely placed, short stalked and borne almost at right angles to the central axis. The head is hemispherical and has a deeply lobed margin. The pollen sacs are "cigar"-shaped and contain bisaccate pollen grains in pollen masses. In P. truncatus, the short stalked microsporophylls are borne in low to high spirals on the central axis at angles ranging between 45°-90°. The elliptical to orbicular head has an entire to occasionally shallowly lobed margin and the pollen sacs are large, "banana"-shaped with untapered truncated apices. The species ofPteruchus described here are very different from all other species so far reported from the Nidpur beds.