New evidence for laurasian corystosperms: Umkomasia from the Upper Triassic of Northern China

Abstract

Recent finds of remarkable fossil plants from the Upper Triassic Yangcaogou Formation in Liaoning Province, PR China include branched, cupule-bearing structures referable to the corystosperm ovulate organ Umkomasia. This material is described and assigned to the proposed new species Umkomasia asiatica. The collection includes numerous isolated cupules and fragments of ultimate cupule-bearing axes. Two specimens consisting of portions of the main axis with attached, cupulate lateral axes have also been found. The main axis was at least 6.5 cm long, with each lateral axis bearing one to at least three pairs of stalked, ovoid cupules. The new Umkomasia is similar to U. franconica from the Jurassic of Germany, which is the only other known laurasian species, but the cupules are smaller and more elongated. It is also similar to many gondwanan forms, including the type species U. macleanii. Leaves associated with the Chinese Umkomasia species are tentatively referred to Thinnfeldia, and may have been produced by the same plant. Associated ovoid seeds with elongated, curved micropyles are similar to those of gondwanan species of Umkomasia. The fossils described here are, therefore, significant in representing the first report of corystosperm reproductive structures from Asia, and only the second report of Umkomasia from the entire northern hemisphere. The new Chinese fossils also support leaf-based evidence that the Corystospermales were present in Laurasia as early as the Late Triassic.