Lower Devonian plant and spore assemblages from Lower Old Red Sandstone strata of Tredomen Quarry, South Wales

Tredomen Quarry, near Brecon, South Wales, is regarded as a Lower Old Red Sandstone terrestrial lagerstatten and has yielded a palaeobotanical assemblage that illustrates the diversity and possible affinities of early vegetation across the Anglo-Welsh Basin during the lower Lochkovian (Early Devonian). Two boreholes were drilled at the site and subsequent logging resolved the stratigraphic position of the quarry to 64 m above the Bishop's Frome Limestone, thus the lower part of the St. Maughans Formation, a level which few other Anglo-Welsh Basin outcrops expose. A palynological assemblage from the quarry surface is assigned to the lower micrornatus-newportensis Sub-biozone of the lower Lochkovian. The assemblage is diverse, a notable characteristic being ornamented hilate cryptospores of which new species and varieties of Cymbohilates are described (Cymbohilates horridus var. A, Cymbohilates cymosus var. A-C, Cymbohilates? sp. A-D). Large rhyniophytes and rhyniophytoids including Cooksonia, Salopella and Tarrantia comprise one component of the palaeobotanical assemblage, typical of southern Britain during the Lochkovian. A diverse group of minute axial plants (mesofossils) constitute a second component, rarely found in other assemblages and considered to be synonymous with the exceptionally well-preserved, charcoalified minute sporangia discovered from a mid-Lochkovian locality. Here they provide for the first time evidence that these minute plants were highly branched and are considered to be stem-group embryophytes with both tracheophytic and bryophytic characters, hence a separate component of vegetation living alongside the rhyniophytes and rhyniophytoids. Non-embryophytes form the third component of vegetation and include Nematasketum/Prototaxites and Pachytheca. Minute coalified banded tubes are observed intertwined across bedding planes and are interpreted as hyphae that may have derived from these non-embryophytes. (C) 2011 Elsevier B.V. All rights reserved.