Vladimariales ordo nov. (Gymnospermae) from the Middle Jurassic deposits of the Mikhailovskii rudnik locality (Kursk Region, European Russia)

Abstract

Composite seed-bearing capsules (formed by fusion of eight radially arranged elementary capsules), assigned to a new monotypic order Vladimariales ordo nov., were found in the Upper Bathonian deposits of the Mikhailovskii rudnik locality (Zheleznogorsk town, Kursk Region). In its morphology, the new order demonstrates valuable, phylogenetically conditioned similarity to Peltaspermales and Umkomasiales, but it is evolutionarily more advanced than these latter. A base of the composite capsule is supported by a collar on a stalk, which in external appearance is not different from collar of Ginkgo L., but has stalk, vascularized in a different way (its conducting tissue consisted of eight radially arranged collateral vascular bundles; each vascular bundle correspond to one of eight fused elementary capsules, each of which contain a solitary seed). Capsules and seeds are inverted relative to the collar; as a result, collar protects micropilar tips of seeds. The presence of collar and whole aspect of the new plant composite capsules give them the significant superficial similarity with seed-bearing organs of modern Ginkgo. Mature composite capsule in Vladimariales ordo nov. dehisced along the lines of fusion of elementary capsules, forming the composite capsule, and scattered seeds; opened composite capsule detached from axis. The significance of the new order for gymnosperm phylogeny is discussed.