Researchers Discover Mysterious Seed Fern
Recently, a mysterious seed fern, Lepidopteris baodensis sp. nov., dating to more than 251 million years ago (Ma), was discovered at the Baijiagou of Baode, Shanxi, China, from the Upper Permian Sunjiagou Formation. This discovery completely changed the understanding of the stratigraphic distribution of the genus Lepidopteris in China and promoted the taxonomic study of late Paleozoic plants.
Since Schimper erected the genus Lepidopteris in 1869, its epidermal structure of subepidermal swellings (formerly called “blisters”) had long been an unsolved mystery. Excitingly, we found subepidermal swellings not only on the lower surfaces of the ultimate rachis and midrib, but also on the lower surfaces of secondary veins. In addition, the unique epidermal structures of subepidermal swellings on the ultimate rachis, midrib and secondary veins were revealed. The epidermis of a subepidermal swelling on an ultimate rachis was composed of ordinary epidermal cells and stomatal apparatuses forming longitudinal rows and numerous groups. The epidermal cells and stomatal apparatuses in each group were set in a concentric pattern. The epidermis of a subepidermal swelling on the midrib was also composed of ordinary epidermal cells and stomatal apparatuses that formed only 3