Silurian thelodonts from the Welsh Borderland and co-occurrence with conodonts

New data on thelodonts from the Middle Llandovery-lowermost Lochkovian of the Welsh Borderland are presented as well as the distribution of co-occurring conodonts. Thelodonts are rare in the Llandovery and Wenlock Series. Like the Wenlock, the basal part of the Ludlow Series is mostly barren of thelodonts but small numbers of the important species Paralogania martinssoni and Thelodus laevis are present with long ranging conodont species of Ozarkodina and Panderodus. In the uppermost part of the Upper Bringewood Formation, Paralogania kaarmisensis and Phlebolepis elegans have been recovered together with the zonal conodont Polygnathoides siluricus (P.C.J. Donoghue and R.E. Elliott pers. comm.). The Whitcliffe Formation, uppermost Ludfordian, provides the most diverse and well-preserved material. Frequent Thelodus parvidens and Thelodus trilobatus occur in association with the rarer zonal conodonts Ozarkodina snajdri, Ozarkodina crispa and Ozarkodina remscheidensis eosteinhornensis. At the base of the Prídolí Series there is a change to a thelodont fauna dominated by Paralogania ludlowiensis, which first appears at this level, in association with Nethertonodus prodigialis. Higher in the Prídolí Series, a succession of thelodont faunas including Katoporodus ?timanicus, Goniporus alatus, Paralogania kummerowi ssp. 1, P. kummerowi ssp. 2 and ?Loganellia unispinata can be traced before the incoming of the lowermost Devonian taxon Turinia pagei along with Nikolivia toombsi. Similarities in thelodont faunas between the Welsh Borderland and the Baltic are presented, showing new correlations in the lower part of the Ludlow Series and uppermost Prídolí Series, where zonal conodont species are extremely rare or absent in Britain.