Tribodus
Tribodus is an extinct genus of hybodont shark from the Romualdo Formation of northeastern Brazil. It lived during the Early Cretaceous. This genus is known from articulated and somewhat complete specimens, from a locality known for the extraordinary preservation of the fossil remains found. Tribodus specimens have been preserved three-dimensionally, and acid-preparation methods have revealed much of the anatomy of this shark.Tribodus is found to have dorsal fin-spines and head spines, though only in males.