A whole noeggerathialean plant Tingia unita Wang from the earliest Permian peat-forming flora, Wuda Coalfield, Inner Mongolia

The genus Tingia Halle is one of the most typical taxa of the Cathaysia Flora. However, its affinity, has long been uncertain. Tingia unita Wang 2006 was named based on the discovery of a crown of a tree that shows the organic connection of the simple compound leaves and the strobili with the stem. It is among the very few species of the Noeggerathiales of which both fertile and sterile parts are known. Since its discovery, a large collection of specimens of Tingia unita has been accumulated from the early Permian peat-forming flora in Wuda Coalfield of Inner Mongolia (Chinese vegetational Pompeii), including various parts of the whole plant. This paper presents a full documentation of this species on the basis of this material, which now, represents the best-known taxon in the genus Tingia and in the order Noeggerathiales. The gross morphology, heterospory and in situ spore morphology, homology of leaf and strobilus, anatomy of the frond and strobilus, and sporophyll arrangement are all known, and conform to a progymnospermous affinity. The plant was an understory tree in the peat swamp forest, approaching the height of tree ferns, whereas Sigillaria Brongniart and Cordaites Unger formed the upper storey. Tingia unita produced a considerable proportion of the biomass of the peat-forming swamp vegetation. This in-depth study contributes to a better understanding of the systematic position of the genus Tingia and the enigmatic group of the Noeggerathiales. •Tingia unita is documented as a nature species with whole plant morphology known.•A reconstruction of the aerial part of T. unita is provided.•Tingia unita is a rare understory tree in the early Permian coal swampy forest.•Tingia unita indicates a progymnosperms affinity of Noeggerathiales.