Anacostia E.M.Friis, P.R.Crane et K.R.Pedersen

Plant Fossil Names Registry Number: PFN001277

Act LSID: urn:lsid:plantfossilnames.org:act:1277

Authors: E. M. Friis, P. R. Crane & K. R. Pedersen

Rank: genus

Reference: Friis, E. M., Crane, P. R. & Pedersen, K. R. (1997): Anacostia, a new basal angiosperm from the Early Cretaceous of North America and Portugal with trichotomocolpate/monocolpate pollen. – Grana 36: 225–244.

Page of description: 227

Type

Original diagnosis/description

Fruiting unit unilocular with a single seed, semicircular to elliptical or irregular in outline; laterally flattened with a straight or convex ventral margin and a strongly convex dorsal margin. Stigma indistinct, apparently sessile. Fruit wall thin, without mechanical tissue; outer epidermis consisting of equiaxial or slightly elongate, polygonal cells with straight anticlinal walls and a striate outer cuticle, sometimes with a central papillate protrusion. Seed anatropous, basally attached; chalaza not visible on the outer surface of the seed; seed wall with a smooth, shiny outer surface. Seed wall apparently bitegmic, formed from two cutinized tissues; outer tissue (testa) sclerenchymatous, consisting of an outer layer of cuboid to palisade-shaped cells with strongly thickened and straight cell walls, a middle layer of shallow cells with thickened and strongly digitate anticlinal walls, and an inner epidermis of shallow cells with straight cell walls; inner tissue (tegmen) thin, membranous and crushed, with transversely aligned thickenings of the tangential cell walls. Pollen (adhering to stigmatic area and surface offrait wall) symmetrical to asymmetrical, monoaperturate with a trichotomocolpate or monocolpate aperture; pollen tectate with graded, reticulate to foveolate tectum and lumina that decrease in size towards the aperture margin and proximal pole; columellae short, densely-spaced, and supporting the psilate muri.

Etymology

From the Anacostia River which passes close to the locality where the type species was recovered.