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Trisquama
Genus Trisquama Gordenko, Broushk. Paleontol. Zhurn., 2018, (1): 88. 2018
- Name
- Trisquama
- Rank
- Genus
- Authors (Pub.)
- Gordenko N. V.
Broushkin A. B.
- Publication
- Semennye organy Trisquamales ordo. nov. (Gymnospermae) iz sredney yury Kurskoy oblasti, Evropeyskaya chast' Rossii [2018]
- Journal
- Paleontologicheskii Zhurnal
- Annee/Jahrgang
- 2018
- Issue
- 1
- Page number
- 88
- Year
- 2018
- Fossil Status
- reproductive organs (seed)
- Type
- Trisquama valentinii
- Diagnosis
- Small ovuliferous organs consist of three thick scales, cup-like fused at base. Free parts of scales encircle inner space of ovuliferous organ, with triangular floor, in central part of which three small orthotropous seeds attached. At base, ovuliferous organ gradually tapers into stalk, crescent shaped in transverse section. Long scale located from side of stalk, and morphologically represents its extension, forming together with stalk sterile structure of ovuliferous organ. Long scale wide, trapezoid in section at its base, then gradually tapers into long subulate apex, which bends toward pair of short scales, covering area of their contact in immature ovuliferous organs, and closing cavity with seeds. Short scales significantly shorter than long one, wider, flattened in transverse section, semicircular in form, terminated by triangular tooth, which bent outwards. At place of junction of short scales, small outgrowth presented; together with short scales it forms fertile (seed-bearing) structure of ovuliferous organ. Through outgrowth and opposed to it long scale, plane of general bilateral symmetry of ovuliferous organ passes; symmetry broken by unequal width of short scales and differences in course of associated with them vascular bundles. In stalk of ovuliferous organ presented single collateral vascular bundle, which possesses in section form of shallow “C” with xylem on concave side, oriented outward of ovuliferous organ. This bundle vascularizes sterile structure of ovuliferous organ, passing immediately into long scale and terminating in its apical part. In lower part of ovuliferous organ, from phloem side of sterile structure vascular bundle, at wide angle amphicribral concentric vascular bundle departs, vascularizing fertile structure of ovuliferous organ. This bundle at its base possesses form of very tall narrow ellipse in transverse section; narrow zone in its central part, corresponded to gap in vascular bundle of sterile structure, consists of f ibers and transfusion cells. Distally, elliptical vascular bundle splits at its upper extremity, becoming ushaped; towards floor of ovuliferous organ, distal bent upward part of this bundle divides into two unequal collateral plates. Shorter plate (right one when ovuliferous organ oriented by floor facing observer and long scale upward; associated with wider of short scales) bent outwards; longer left plate, hookshaped in transverse section, divides again. Finally resulting three plates in their position correspond to two short scales and outgrowth between them, and also to three seeds, situated from xylem side of these vascular bundles. Beneath floor of ovuliferous organ these bundles wedge out, replaced by mass of transfusion tissue. Free parts of short scales not vascularized. Cortex of ovuliferous organ consists of two zones, outer of which sclerified; secretory canals and cavities absent. Cuticular covering of ovuliferous organ thin, epidermis of outer surface with numerous monocyclic stomata, epidermis of inner surface of scales without stomata, in short scales with thinly cutinized papillae. Seeds ellipsoidal, with not protruding micropyle, somewhat shifted relative to longitudinal axis of seed. Integument three layered, consists of exotesta (epidermis), sclerified mesotesta, and multilayered papery endotesta. Nucellus free from integument more than one half, megaspore membrane thick.
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