Naiadita lanceolata (Marchantiophyta) from the Middle Triassic (Ladinian) of Germany: a new reconstruction attempt and considerations on taphonomy

The fossil liverwort Naiadita lanceolata is described here from lacustrine deposits occurring intercalated in the Albertibank complex of the Lower Keuper, Erfurt Formation (Ladinian, Middle Triassic) of Schleerieth, northern Bavaria, Germany. The specimens represent the stratigraphically oldest records of this taxon so far. Leafy gametophytic plants are preserved as impression-compression fossils and include four specimens also showing the terminal or subterminal sporophyte in situ, as well as four leafy stems bearing conical gemma cups with lobed margins. Based on the new material, a refined reconstruction of N. lanceolata is proposed. The new found specimens also shed light on some plant taphonomic processes. The monospecific N. lanceolata assemblages comprise mostly leafy gametophytic stems, often still showing the three-dimensional orientation of the foliage. Another peculiar characteristic is the mass accumulation of isolated sporophyte capsules, which are partially surrounded by perianth leaves, probably a useful propagule mechanism for the cleistocarpous capsules.