The recent discovery of a plant zone containing Lyginopteris (Calymmatotheca) stangeri at Penderyn, on the North Crop of the south Wales coal field, as well as other plant occurrences in the Neath valley area, indicates the presence of the Eumorphoceras stage of the Namurian (upper Carboniferous), which requires reinterpretation of the Avonian and Namurian succession.

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