The oldest acanthomorph fossil (Actinopterygii, Teleostei) from the Early Cretaceous of Gondwana (Morro do Chaves Formation, Sergipe–Alagoas Basin, NE Brazil)

Abstract This paper presents the discovery of † Gondwanacanthus decollatus , a new genus and species of Early Cretaceous deep‐bodied fish from the late Barremian or early Aptian Morro do Chaves Formation in the Sergipe–Alagoas Basin, northeastern Brazil. It represents the first record of Acanthomorpha in Early Cretaceous Gondwana. This discovery extends the temporal and spatial range of Acanthomorpha and challenges previous biogeographic hypotheses about the origin and diversification of that clade. † Gondwanacanthus decollatus exhibits key morphological features, including unsegmented dorsal‐fin and pelvic‐fin spines, spinoid scales, a pelvic fin‐ray formula of I,5, thoracic pelvic fin insertion and a caudal skeleton consistent with Acanthomorpha. These characteristics align it with Acanthomorpha, a group known for its remarkable diversity among modern ray‐finned fishes. This find fills a substantial gap in the fossil record, particularly during the Early Cretaceous, a period previously underrepresented in acanthomorph evolution. The discovery challenges earlier views on the biogeographic history of the group and suggests a more complex narrative regarding the early evolution and spread of spiny‐rayed fishes.