Zirabia cylindrica comb. nov. provides evidence of Doyleales in the Jurassic.

Abstract

In recent years, Doyleales have played an important role in the discussion and exploration of seed plant relationships and the origin of angiosperms. This order comprises a diversity of recently described genera with cupule-bearing compound ovulate cones recovered from Early Cretaceous deposits in North America and Asia. Their relatively late appearance in the fossil record, stratigraphically near the appearance of angiosperms in the Early Cretaceous, has been noteworthy. Here, we report a new genus of Doyleales, Zirabia gen. nov. from the Early Jurassic of Iran, that was originally described as the ginkgophyte Karkenia. We reinvestigated material previously assigned to Karkenia cylindrica from the Lower Jurassic of the Zirab locality, Alborz Mountains, northern Iran. The studied specimen features a main axis bearing helically to irregularly arranged bract-cupule complexes, each composed by a long laminar bract subtending and sheathing a cupule stalk that bears a single-seeded cupule with a dorsal protrusion. The morphological features of this taxon do not conform with those of Karkenia, and suggest affinities with Doyleales rather than Ginkgoales. Within Doyleales, this fossil has a unique combination of characters indicating that it is a new genus within the order; thus, a new combination is erected, Zirabia cylindrica. Our results indicate that Doyleales is significantly older than previously thought, with their stratigraphic range now extending from the Lower Jurassic to the Cretaceous. The Early Jurassic occurrence of Doyleales provides important data on the emergence of seed-enclosing structures seen in seed plants throughout the Mesozoic.