Ovuliferous Organs of Trisquamales Gordenko et Broushkin Ordo Nov. (Gymnospermae) from the Middle Jurassic of the Kursk Region, European Russia
From the Bathonian deposits of Mikhailovskii Rudnik locality (Kursk Region) ovuliferous organs Trisquama valentinii Gordenko et Broushkin, gen. et sp. nov. are described. The ovuliferous organs consist of three scales fused at the base. The long scale together with the stalk of ovuliferous organ constitute sterile structure, which is vascularized by C-shaped in section collateral vascular bundle, and bears lobed fertile structure of ovuliferous organ on its anatomically abaxial side. The latter consists of two short scales and the outgrowth between them, and is vascularized by concentric amphicribral vascular bundle, which divides in its distal part into three separate collateral plates. These plates are associated with the lobes of fertile structure and three small orthotropous seeds, situated from xylem side of these vascular bundles. Seeds are ellipsoidal, with unprominent micropyle; the integument is sclerified, megaspore membrane is thick. The ovuliferous organs under description possess unique features, which do not allow their assignment to any large group of gymnosperms; authors place them in separate order Trisquamales ordo nov., systematic position of which within Gymnospermae is uncertain.