The fossil record of marine fishes from the Upper Carboniferous and Permian is poor (Sepkoski, 2002), and the Bear Gulch fauna has gained significance as a marker for early representatives of clades known otherwise only from much more recent deposits (Hurley et al., 2007). This raises questions about sampling error: whether fish diversity at other relevant localities has been misinterpreted or overlooked. Here, we report new discoveries of fishes from lateral equivalents of the Bearsden locality. Discovered and prepared by Patrick Gavin, these fossils show that the range of Bearsden fishes overlaps that of the Bear Gulch fauna to an extent much greater than previously suspected, including groups until now known only from North America. These new discoveries support the suggestion that Carboniferous fish diversity is significantly under-determined.