The first record of the Gondwanan seed fern Dicroidium Gothan in Laurasia

Abstract

Dicroidium Gothan is an extinct seed fern that was widely distributed in Gondwana during the Triassic but has not yet been unequivocally recorded in Laurasia. In this paper, a new species of the genus, Dicroidium sinensis Sun et Deng sp. nov., is described from the Middle Triassic sediments of the Ordos Basin, northwestern China, based on macromorphology and cuticular structures. This is the first record of Dicroidium in China, indicating that the genus was not unique to Gondwana and was also present in Laurasia. Dicroidium seems to have originated in the palaeotropics in the Permian (e.g., Jordan) and then widespread and flourished in Gondwana and extended to Laurasia during the Middle-Late Triassic period, and disappeared in the Early Jurassic. This genus may have migrated from Jordan to Laurasia along the western coast of the Tethys. Additionally, galls found in the leaf of Dicroidium sinensis proves the interactions between plants and insects.