Tribodus

Tribodus is an extinct genus of hybodont shark from the Santana Formation (from the Early Cretaceous Epoch, some 110 mya) of northeastern Brazil. It is known from articulated (meaning that the bones are attached to one another in a lifelike manner) and somewhat complete specimens, from a locality famous for the extraordinary preservation of its fossils. Specimens of Tribodus have been preserved three-dimensionally, and acid-preparation methods (in which the rock matrix is chemically removed from the mineralized skeleton) have revealed much of the anatomy of this hybodont shark. As with the other genera of hybodonts, Tribodus has dorsal fin-spines and head spines (in males only).