Neotypes for some upper Silurian acanthodian taxa from the Baltic Sea Region and the Welsh Borderland

The type material of acanthodian taxa from the upper Silurian of Estonia, erected by C. Pander and V. Rohon in the nineteenth century, has long been lost, and in most cases no neotypes have been erected to date. We nominate scales of Nostolepis striata Pander and Gomphonchus sandelensis (Pander) from the type locality at the Ohesaare Cliff, Saaremaa Island, Estonia, as neotypes for those two species. We also nominate a replacement neotype scale for Radioporacanthodes biblicus (Lehman) from the vicinity of the type locality at Ramsåsa, southern Sweden, to replace the invalid neotype from a borehole on Saaremaa Island. The validity and distribution of Gomphonchus volborthi (Rohon) is considered, and a neotype and type stratum (the Ludlow Bone Bed, Shropshire) are designated. Specimen repository details, where not provided in the original descriptions, are listed for other acanthodian scale-based taxa from the Baltic Sea Region.