Acanthodes lopatini from the earliest Tournaisian of East Greenland links vertebrate faunas of Euramerica and Siberia.

In this contribution, we present the first full description of acanthodian fossils from the early Tournaisian (Carboniferous) Obrutschew Bjerg Formation (OBFm) deposits on Celsius Bjerg, East Greenland, with comparative morphological and anatomical analyses aimed at clarifying their taxonomic affinities. The OBFm outcrops on Celsius Bjerg document both the latest Devonian Hangenberg event and the Devonian-Carboniferous boundary, and thus provide a rare window into conditions in a continental lacustrine environment during the event and its immediate aftermath, providing valuable insight into faunal recovery and turnover during this interval. Our work broadens current understanding of the early Carboniferous vertebrate assemblage present in the OBFm, which despite its significance has remained poorly characterized owing to sparse sampling. Our analysis supports conferring this material to Acanthodes lopatini Rohon, 1889 (sensu Beznosov 2007), a taxon previously known only from the early Carboniferous of Siberia. We note multiple stages of ontogenetic maturity among our specimens and build on existing studies of acanthodian ontogeny with new observations. We also comment on the wider palaeogeographical and palaeoecological context of our material, and consider the place of these fish in relation to the upheaval and recovery of vertebrate communities in the wake of the end-Devonian extinctions.