In Mongolia, plants preserved in a volcanic ash fall deposit as part of a so-called \"vegetational Pompeii,\" may have resolved the mystery of the Noeggerathiales.What are Noeggerathiales? Paleontologists have wanted to really know since they first learned of them.Scientists know they were peat-forming plants that lived approximately 325-251 million years ago but their relationships with other plant groups was unknown. Now it has been established that Noeggerathiales had the spore propagation mode of ferns and the vascular tissue of seed plants. They belonged to a sister group of seed plants, the former gymnosperm.The researchers studied complete plants preserved in a 66-cm-thick bed of volcanic ash that fell 298 million years ago and smothered all the plants growing in a swamp. The ongoing research based on the fossils from the 'vegetational Pompeii' may bring about more and more reconstruction of ancient plants,\" said Professor Wang Jun from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences.