Article: Early Ordovician (Arenig) bivalves from the Llangynog Inlier, South Wales

The most diverse early Ordovician bivalve fauna yet known comprises 20 species belonging to 18 genera. It is from the early Arenig (Moridunian Stage) of the Llangynog Inlier, near Carmarthen. South Wales, and is dominated by actinodontoids. with palaeolaxodonts, cyrtodontoids and rarer modiomorphoids, anomalodesmaians, solemyoids and a pterioid. From the same locality a rostroconch is described and a nearby mid-Arenig (Whitlandian Stage) locality has yielded an ambonyehiid. The following new taxa are described: Pensarnia laeviformis gen. el sp. nov., Paulinea parva gen. et sp. nov.. Ovatoconcha fragilis gen. el sp. nov., Glyptarca serrata sp. nov., Carminodonta crossi gen. ct sp. nov.. Fortowensia grandis gen. et sp. nov.. Celtoconcha foveata gen. et sp. nov.. Moridunia simplicidens gen. et sp. nov.. Goniophoria (Cosmogoniophorina} extensa sp. nov., Parallelodus dyfedensis sp. nov., Falcatodonta costata gen. el sp. nov. and Arenigomya carinata gen. et sp. nov. The new genus Hemiprionodonta is introduced for forms previously described from the middle Ordovician of France and Iberia, and From the upper Ordovician of North Wales. The following higher level laxa are proposed: Superfamily Glyptarcoidea. Family Glyptarcidae. Order Cyrtodontida. Superfamily Falcatodonloidea and Family Falcatodontidae. The fauna includes the earliest known representatives of the solemyoids, pterioids and anomalodesmatans.