New fossil material of <i>Equicalastrobus</i> (Equisetales) and associated leaves from the Late Triassic of Baojishan basin, Gansu Province, China

A new species of Equicalastrobus pusillus L. Zhang et D.F. Yan sp. nov. and associated leaves Schizoneura koningensis were reported from the Late Triassic of Baojishan basin, Gansu Province, China. Cones found here were spicate, with peltate discs surrounding the axis, and the leaf-like umbo projections were identifiably smaller in size compared to the type species. Sporangiophores showed a loose arrangement implying the cones had been expanded before they were buried. Associated leaves were attributed to Schizoneura koningensis, due to their characteristic features. In order to discuss the relationship of fertile genus Equicalastrobus with other Equisetales cones, a clustering analysis on characters of reproductive organs covering 46 equisetalean cones (14 extant and 32 extinct) was performed. The character matrix was based on 36 discrete characters and 6 continuous characters. According to the clustering result, it was suggested that the new species, as well as the genus Equicalastrobus had a closer relationship with Equisetum-type cones, rather than Calamites-type cones. The co-occurrence of the two genera, Equicalastrobus and Schizoneura, demonstrated a wide distribution of equisetaleans with a rich and diverse morphology around the Triassic World.