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Abstract Detail



The Devonian Period: a time of major plant diversification: a symposium in honor of Patricia G. Gensel and her contributions to Devonian paleobotany.

Edwards, Dianne [1].

Hooker's waifs and strays revisited.

In 1990, Gensel and colleagues reviewed a number of enigmatic Mid Palaeozoic fossils including Prototaxites and Pachytheca, whose affinities remain equivocal and controversial today. A number of these had been earlier united by W H Lang in the Nematophytales who considered them neither algal nor terrestrial plants while colonizers of the subaerial environment in the Silurian and Devonian. Here I will present both anatomical and geochemical data relevant to the affinities of Prototaxites and Nematothallus. The latter is reconstructed as a thalloid soil or rock encrusting organism with stratified tissues comprising three layers.The uppermost single layer of 'cells' is usually represented in the dispersed record by 'cuticles' with a reticulate patterning of ridges. Below this is a zone of filaments orientated perpendicular to the surface. This overlies wefts of much narrower occasionally branched tubes. Similar organization is noted in Cosmochlaina. Although Nematothallus has been recently interpreted as a marine noncalcified coralline red alga from perforated cuticles originally assigned to Nematothallus, the complexity of organization described here shows greater similarities with that in macrofungi and, in the presence of a superficial 'cortex', possibly with lichens, although there is no evidence of a photobiont. The presence of the Nematothallus complex in fluvial rocks in the Welsh Borderland negates affinity with seaweeds, while preservation as charcoal and consistant association with higher plants is evidence for a terrestrial source. Preliminary geochemical analyses detract from an algal or embryophyte affinity.

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1 - Cardiff University, Earth and Ocean Sciences, Main Building , Park Place, , Cardiff , CF10 3AT, UK

Keywords:
none specified

Presentation Type: Symposium or Colloquium Presentation
Session: SY10
Location: Prince of Wales/Riverside Hilton
Date: Wednesday, July 31st, 2013
Time: 8:45 AM
Number: SY10003
Abstract ID:292
Candidate for Awards:None


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