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The genus Hybodus is represented in the fossil records of Asia, Europe, Africa and North America
by skeletons, isolated teeth, cephalic and fin spines. According to Maisey (1996), these were marine
sharks, but some species would enter freshwater.
North American species include 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 an undescribed species
found in Campanian deposits from New Jersey to Georgia. Welton & Farish (1993) list a
Hybodus sp from the Cenomanian-Coniacian deposits of Texas. These Texas teeth appear quite
similar to the unnamed species of the East Coast. In addition to Hybodus sp and based on
damaged teeth, Kent (1994) speculates on the presence of H. montanensis in the Chesapeake
Bay region. Robb (1989) includes of H. montanensis in the Black Creek Group based on dorsal spines.
Cappetta (1987) describes the 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.
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