Cnap Twt

Site of Special Scientific Interest · 51.4667, -3.5701

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Also within

South Glamorgan County

Habitats

Fast flowing river and stream

Geology & landscape

Geological Feature: Fissure · Mining / Industrial: Quarry · Geological Period: Carboniferous · Rock Type: Carboniferous Limestone, Limestone

Description

Description Cnap Twt is a small disused quarry in the valley of the River Alun approximately 3 miles to the south of Bridgend. The site is of national importance for fossil plant remains. Cnap Twt is the best locality for the floras preserved in Rhaetian fissure-fillings within the Carboniferous Limestone of south-west Britain. The flora is dominated by cheirolepidacean conifers, one of the primitive families which are believed to be the precursors of all living conifers. It is one of the earliest occurances of this family anywhere in the world, and is of particular interest because of the unusually fine, uncompressed preservation of the specimens. Fragments of bennettites and other conifers have also reported from here, but have yet to be studied in detail. A site of outstanding palaeobotanical significance.

Plant communities

A9 — Fast flowing river and stream, Marginal and inundation, Pond ditch and canal, Sluggish river and stream

Potamogeton natans community

Schoenoplectus lacustris, Juncus bulbosus, Sparganium angustifolium, Sparganium erectum, Sparganium minimum, Alisma plantago-aquatica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Elodea canadensis, Lemna minor, Lemna trisulca, Nymphaea alba, Callitriche platycarpa, Callitriche stagnalis, Littorella uniflora, Potamogeton natans, Ranunculus trichophyllus, Glyceria fluitans, Chara subspinosa

A14 — Fast flowing river and stream

Myriophyllum alterniflorum community

Isolepis fluitans, Juncus bulbosus, Fontinalis antipyretica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Lemna minor, Callitriche stagnalis, Littorella uniflora, Potamogeton filiformis, Potamogeton gramineus, Potamogeton natans, Ranunculus peltatus, Chara spp., Nitella hyalina

A17 — Chalk river and stream, Fast flowing river and stream

Ranunculus penicillatus ssp. pseudofluitans community

Berula erecta, Nasturtium officinale, Elodea canadensis, Lemna minor, Callitriche stagnalis, Veronica beccabunga, Polygonum amphibium, Polygonum hydropiper, Potamogeton crispus, Potamogeton pectinatus, Ranunculus penicillatus ssp. pseudofluitans

A18 — Fast flowing river and stream

Ranunculus fluitans community

Fontinalis antipyretica, Fontinalis squamosa var. curnowii, Myriophyllum alterniflorum, Myriophyllum spicatum, Elodea canadensis, Mentha aquatica, Lemna gibba, Lemna minor, Potamogeton perfoliatus, Ranunculus fluitans, Glyceria fluitans, Phalaris arundinacea