Gopadispermum

Bhowmik, Nupur & Parveen, Shabnam, 2014, Fossilized pollination droplet in a new seed genus from the Middle Triassic of Nidpur, India, Acta Palaeontologica Polonica 59 (2), pp. 491-503 : 493

Genus Gopadispermum nov.

Etymology: In reference to the river Gopad in Sidhi District, Madhya Pradesh, India. The Middle Triassic beds of Nidpur are situated along the banks of the river.

Type species: Gopadispermum papillatus sp. nov., see below; monotypic.

Diagnosis.—Seeds small, platyspermic, orthotropous, rounded to broadly oblong, micropylar end rounded, with a short straight mucronate micropylar tube. Chalazal end rounded, with a shallowly concave, narrow chalazal hole at centre. Surface of seed generally smooth. Seed outline often irregular due to a persistently attached incompletely preserved carbonaceous layer outside seed coat. Micropylar canal often extended beyond adhering tissue. Outer cuticle of integument thin, delicate, papillate. Inner cuticle of integument thin, delicate, granular, extended apically to form a short micropylar tube. Nucellar cuticle tough, appressed to inner cuticle upto chalazal hole, cell walls conspicuously sinuous. Megaspore membrane large, rounded, tough. Pollen chamber dark, collar-like at base, generally containing clumps of compactly adherent saccate pollen grains. External carbonaceous layer yielding two non-stomatiferous cuticles on maceration. Pollination by droplet mechanism.

Remarks.—The genus Gopadispermum is instituted to include small, dispersed seeds exhibiting the following features: pollination by droplet mechanism, droplet substance showing a few entrapped saccate pollen grains, a collar-like pollen chamber below the short micropyle containing saccate pollen grains frequently occurring in clumps. In addition to the above features, seeds of Gopadispermum generally lack surface wrinkles and show a delicate outer cuticle of integument, suggesting the possibility of seeds having occurred sheltered inside a cupular or protective structure rather than having been borne exposed. No seed specimen was howev- er, found completely enclosed within a cupulate structure, although several of them exhibited an irregular seed outline, due to the presence of the closely adhering carbonaceous tissue external to the seed coat. The short straight micropyle often extended beyond the margin of the cupule-like tissue as is reported in seeds of Corystosperms ( Thomas 1933). The characters of Gopadispermum are unique and interesting and to the best of our knowledge, no earlier described seed morphotaxon from the Nidpur Triassic has reportedly exhibited similar features. Therefore, we consider it reasonable to institute a new genus for this fossil seed.

Stratigraphic and geographic range.—Middle Triassic of Nidpur, Madhya Pradesh, India.