New insights into the moss genus Vetiplanaxis with a description of V. obtusus sp. nov. from the mid-Cretaceous Kachin amber, Myanmar

Molecular phylogenetic analyses indicate that during the Cretaceous Terrestrial Revolution (KTR) around 125-80 Ma, the rapid rise and radiation of angiosperms probably triggered the diversification of mosses and substantial changes of their lineage composition. However, moss fossils which could substantiate these findings are generally rare in the Cretaceous. In this study, we investigate several sterile gametophyte fragments of mosses preserved in mid-Cretaceous Kachin amber from Myanmar. We describe a new sterile shoot as Vetiplanaxis obtusus sp. nov. (Hypnodendrales), make an emended description of V. pyrrhobryoides Bell based on additional fossil materials, and identify a linear-lanceolate leaf as V. cf. longiacuminatus Hedenäs et al. We confirm again the presence of geminate teeth in leaf margin of the above three species studied here, and report the presence of hair-like rhizoids in stem. The phyllotaxis in the species of Vetiplanaxis with complanate shoot is explained as pseudo-tetrastichous, really octostichous, formed by two right-handed Fibonacci spirals. Our findings provide new insights into the circumscription of the Cretaceous moss genus Vetiplanaxis, and add new evidence to indicate that there was a diverse pleurocarpous moss flora in the mid-Cretaceous Kachin amber forest of Myanmar.