Progress in reconstructing vegetation on the Old Red Sandstone Continent: two Emphanisporites producers from the Lochkovian sequence of the Welsh Borderland

Abstract

AbstractSmall coalified fossils (mesofossils) have yielded new insights into vegetation of the Old Red Sandstone Continent in early Devonian times. Particularly useful are those containing spores that can be placed in dispersed spore taxa, although patinate and emphanoid spores have not hitherto been found in situ. Emphanisporites cf. micrornatus Richardson & Lister is described in a bifurcating cylindrical sporangium preserved as a cuticular sheath. A terminal dehiscence feature is compared with that in Horneophyton. The sporangium is encased in amorphous detritus with some tubular fragments. Similar associations occur on other sporangia, e.g. Tortilicaulis and axes at this North Brown Clee Hill locality, and they are interpreted as remains of a microbial or fungal film. Fragmentary cuticles, interpreted as isolated sporangial valves, bear an undescribed species of Emphanisporites with fine interdigitating proximal muri and laevigate distal surfaces referred to Emphanisporites sp. A Richardson & Lister. Analysis of dispersed spore assemblages from the locality and others in the Welsh Borderland indicate that the two emphanoid taxa were not common components of the spore ‘rain’. This evidence, coupled with the dearth of mesofossils of the producers, suggests that the plants grew at the upper reaches of the drainage basin of the river that deposited the sediment, although the paucity of sporangia may also be attributed to their low fossilization potential.