Nosova N., Kostina E., Afonin M.
В журнале Review of Palaeobotany and Palynology
Год: 2023 Том: 315 ArticleID: 104907
Ovule-bearing structures of Karkenia are recorded from the Cretaceous of Central Mongolia for the first time. A new species, Karkenia archangelskiana, described from the Aptian–Albian Huhteeg Formation of the Baganuur coal mine, is an elongated cylindrical ovule-bearing structure consisting of a central axis and helically arranged pedicellate ovules which are rare in the basal part of the structure, and gradually more numerous towards its apex. Some ovules face the pedicel with their micropylar end, but others seem to be erect. Four membranes are preserved in the ovules: outer and inner cuticles of the integument, the nucellar cuticle, and the megaspore membrane. Numerous isolated seeds/ovules were found in the same specimens that yielded ovule-bearing structures and may represent more mature units of K. archangelskiana. Fragments of the secondary xylem were discovered in association with K. archangelskiana. They show some similarities with the structure of the mature trunk or branch ginkgoalean wood. Ovule-bearing structures of K. archangelskiana were found in association with numerous remains of wedge-shaped leaves described as a new species Sphenobaiera krassilovii. This species is peculiar in possessing narrow segments, one vein in the ultimate segments, and stomata scattered irregularly over both surfaces. In addition, ovule-bearing structures of Karkenia mongolica from the Lower Cretaceous of southeastern Mongolia were revised. For the first time, a megaspore membrane structure of the K. mongolica ovules was studied. The species diagnosis is emended by adding such features as the presence of papillae on the subsidiary cells of some stomatal apparatus, and the data concerning the megaspore membrane structure.
