Nidianthus gen. nov. - A Caytonanthus - like pollen organ from the Triassic of Nidpur, M.P., India

Abstract

Nidianthus indicus gen. et sp. nov. is a synangiate pollen organ represented by more than 30 detached specimens. The compressed synangia were isolated from the Nidpur beds by bulk maceration of the Triassic shale in HF. Each synangium is elongated, radially symmetrical, appearing four-winged with a short axial attachment at base possibly representing ultimate branchlet. The four elongated pollen sacs remain attached at the base of synangium but appearing attached or free in middle and apical regions leaving four gaps at the time of dehiscence. The apical region of each pollen sac is pointed and bent inward towards the centre of synangium. Each pollen sac dehisces by a longitudinal slit along the midline of inner face. The surface of pollen sacs shows longitudinal striations. Some specimens showed a quadrangular abscission scar at the base of synangium. Cuticle of pollen sac wall showed elongated, rectangular to polygonal cells seemingly arranged in longitudinal files. Anticlinal walls thin, obscure, straight or slightly waved. Cells become narrow towards the inner margin. Many cells of pollen sac wall showed median papilla bases and cells near the apical region showed cutinized unicellular hairs. Sometimes, remains of an inner, obscurely cellular, granular membrane possibly representing a tapetal layer could also be seen on inner side of pollen sac wall. Inside each pollen sac is a single mass of pollen-grains. Pollen-grains bisaccate, bladders hemispherical or obovate showing irregular surface reticulum, Nidianthus gen. nov. closely resembles the anther-like pollen organ Caytonanthus of Caytoniales.