Direct evidence of shark-bony fish interactions in a Valanginian (Early Cretaceous) marine ecosystem of northwestern Gondwana

Direct fossil evidence of predator-prey interactions among marine vertebrates from the Early Cretaceous of northern South America is extremely scarce, limiting our understanding of the trophic dynamics in ancient Gondwanan ecosystems. Here, we describe a partially preserved left posterior jaw ramus of a teleost fish from the Early Cretaceous Rosa Blanca Formation in Colombia. It includes fused dentary, anguloarticular, and retroarticular bones, a condition observed in stem pholidophorids and more derived teleosts. CT scans revealed distinct internal structures between the dentary and anguloarticular bones, and the corresponding external bone textures also differed. Embedded in the lateral surface of the angulo-articular is a broken shark tooth with a lanceolate shape and apparent serrations. SEM imaging revealed a two-layer structure: an outer enameloid and an inner osteodentine core. The absence of a pulp cavity and complete mineralization of the axial surface indicate an osteodont tooth type, typical of lamniform sharks. This represents the first direct evidence of a trophic interaction between lamniform sharks and teleost fish from northern Gondwana during the Cretaceous. This discovery adds to the known vertebrate diversity of the formation and mirrors modern ecological dynamics, in which lamniform sharks prey on bony fishes. This also supports the interpretation of a complex marine ecosystem in the region, previously evidenced by the remains of pliosaurs, plesiosaurs, metriorhynchids, and pterosaurs. This finding complements earlier indirect evidence of shark predation and enriches our understanding of Cretaceous marine food webs in the tropical Gondwanan settings.