Hybodus

Hybodus is a genus of extinct shark represented in the fossil records of Asia, Europe, Africa and North America by skeletons, isolated teeth, and head and fin spines. According to Maisey (1996: 104-06), these were marine sharks, but some species would enter freshwater.

North America

 * H. nevadensis WEMPLE 1906 (Middle Triassic of Nevada),
 * H. shastensis WEMPLE 1906 (Upper Triassic of California),
 * H. montanensis CASE 1978 (Campanian, Upper Cretaceous of Montana),
 * H. butleri THURMOND 1971 (Aptian-Albian of Texas) and
 * Hybodus sp, an undescribed species found in Campanian deposits from New Jersey to Georgia.

Teeth
Hybodus dentition as generally being a clutching-type. Later, in some species, the central cusps are larger and lateral(s) reduced, creating a tearing-type dentition. The Hybodus tooth is laterally expanded (to 2 cm) with a large central cusp bearing enameloid ridges and a distinct cutting edge. One or more, smaller, lateral cusps are present. The (weakly) lingually directed root is relatively short and thin. The basal and lingual faces have numerous scattered foramina.

Isolated teeth from this genus are usually fragmentary and lacking roots. Elongated, knife-like dorsal spines are relatively common. Those from Hybodus sp. are covered with enameloid tubercles (laterally) and have a serrate posterior edge. The H. montanensis dorsal spine is similar, but has elongated enameloid ridges on the side and is thicker in cross-section.