Karkenia bracteata A.O.Frolov, Enushchenko et I.M.Mashchuk

Plant Fossil Names Registry Number: PFN003485

Act LSID: urn:lsid:plantfossilnames.org:act:3485

Authors: A. O. Frolov, I. V. Enushchenko & I. M. Mashchuk

Rank: species

Reference for this name: Frolov, A. O., Enushchenko, I. V. & Mashchuk, I. M. (2025): A new species of Karkenia (Karkeniaceae, Ginkgoales) from the Early Jurassic of the East Siberia (Russia): Paleobiogeographical and Evolutionary implications. – Papers in Palaeontology 11(3): e70019., link

Page of description: 3-5

Illustrations or figures: Figs 2–6, 7A–C

Types

Original diagnosis/description

Megastrobiles loose, cylindrical, consisting of central axis bearing more than 20 spirally arranged ovules. Its apex ends in two terminal ovules, smaller in size than in middle part of megastrobilus. Ovules anatropic, ovoid with rounded chalazal end, tapering to micropyle directed towards central axis of megastrobilus. Ovule stalks long gradually expand towards base of ovule and end in short acute apical projection. At base of ovule stalk there is a bract, which grows together with ovule stalk approximately to middle of its length. Free part of bract laminar, entire, long, gradually narrowing to sharp subulate apex. Integument epidermis composed of rectangular and fusiform cells with straight or slightly curved, uniformly thickened anticlinal walls. Periclinal walls of some cells bear flat papilla, rarely short trichomes. Stomatal complexes oval elongated, monocyclic with broken outline. Guard cells not sunken and surrounded by 7 subsidiary cells, which not differ from ordinary cells in degree of cutinization. Megaspore membrane consists of thin foot layer and thick patterned layer. Patterned layer composed of crowded small bacula arranged perpendicular or oblique to foot layer. Foot layer uniform and smooth.

Etymology

Species epithet bractea (lat.) is based on the presence of bracts partially fused with the ovule stalks.

Stratigraphy

Jurassic, Lower Jurassic, Toarcian
The Middle member of the Prisayan Formation of the Irkutsk Coal Basin.

Locality

Russian Federation
Right bank of the Angara River, Sukhov cape locality (52°30012.600N 103°59007.400E)