The early actinopterygian genus <i>Rhadinichthys</i> redefined, the type species <i>ornatissimus</i> redescribed, and the species <i>bearsdeni</i> introduced

ABSTRACT Rhadinichthys is one of the most wide-ranging and speciose genera of Palaeozoic actinopterygians. A classic variety of ‘palaeoniscoid’, Rhadinichthys species are generally small (~10–15 cm) and known mostly from dermal skeletal remains that show features commonplace among early ray-finned fishes. For this reason, the genus has long been considered a poorly diagnosed wastebasket taxon in need of revision and rarely included in systematic analyses. In the present work, syntypes of Rhadinichthys ornatissimus , the type species, are re-examined and supplemented with better-preserved material from other localities in the Scottish Midland Valley. A neotype is nominated and a more precise diagnosis presented with a suite of genus-level apomorphies. Unexpectedly, these traits are also evident in the monotypic Lower Carboniferous actinopterygian genus Woodichthys , which the neotype of R. ornatissimus closely resembles. As a result, the genus Woodichthys is subsumed within the redefined Rhadinichthys , and the single Woodichthys species is reassigned as R. bearsdeni , comb. nov., bringing with it a set of endoskeletal data. Some of these data are new, derived from μCT scans of the skull of the R. bearsdeni holotype, yielding renderings that update the original description of its skull table, parasphenoid, neurocranium, and otoliths. Further new data concerning the hyoid arch are obtained from a new specimen of R. bearsdeni from a site close by the original Bearsden locality. Redefined in this way, Rhadinichthys presents a data-rich operational taxonomic unit better suited for systematic studies. However, in so doing, it also releases a cluster of fossil species no longer anchored to a genus and now in need of rediagnoses.