First Late Cretaceous ichthyofauna from the Kababish Formation and its paleoenvironmental significance and paleogeographic implications

This study documents the first record of a fossil fish assemblage from the Upper Cretaceous Kababish Formation of north-central Sudan, associated with the dyrosaurid crocodyliform Brachiosuchus kababishensis . The identified taxa include the nurse shark Nebrius sp., a pycnodontid tooth, and a hybodontiform dorsal fin spine. Although limited in diversity, the assemblage provides new data on the poorly known Late Cretaceous ichthyofauna of the region. Sedimentological and ichnological observations suggest deposition in a shallow, tide-influenced marginal-marine setting, while the ecological affinities of the recovered ichthyofauna are consistent with a nearshore coastal environment. Although these independent lines of evidence converge on the same paleoenvironmental interpretation, the limited size and diversity of the assemblage preclude definitive conclusions and highlight the need for additional fossil material to evaluate this interpretation further. In a broader paleobiogeographic context, the occurrence of these taxa suggests regional geological and paleontological evidence for marine influence extending into north-central Sudan during the Late Cretaceous. The discovery contributes to the growing record of Late Cretaceous vertebrates from Sudan. It demonstrates the scientific value of micro-vertebrate recovery, as the remains were obtained during preparation of the associated dyrosaurid specimen rather than through targeted collection. Future systematic sampling of the Kababish Formation is expected to improve understanding of the diversity, paleoenvironment, and paleobiogeographic relationships of Late Cretaceous vertebrate assemblages in the area and northeastern Africa.