Description: The anterior teeth have straight angled, broad, and flattened main cusps.  The angle is more slanted and the main cups more reduced in the lateral and posterior teeth.  The cusplets appear as small raised bumps along the enamel margin close to the root.  All teeth have a shallow nutrient groove on the medial portion of the root.  The usual length of these teeth is about 1 cm (about .5 in).

Commonality: Thresher shark teeth are commonly to less commonly found at this locality.

Similar fossils: The teeth are similar to the porbeagle shark, Archaelamna, but there are some distinguishing features that differentiate them.  The main cusp is thinner on edge than that of the porbeagle.  The main difference is in the cusplets, which are very small and attached to the main cusp and look like small raised bumps.  The other difference is the main cusp in lateral and posterior teeth do not curve form the root as the porbeagle shark has, but are slanted from the root.

Size: They ranged about 2 to 30 meters (about 7 to 10 feet) in length.

Notes: The lifestyle of the fossil thresher shark was probably similar to the porbeagles and the modern day threshers.  Modern day threshers are open water sharks that feed on small to medium sized schooling type fish.  Their bodies were somewhat stocky in appearance and possessed an elongated top fin on their tail. It is hard to say whether this ancient thresher possessed these qualities because only fragmented fossil evidence has been recovered.  The threshers seemed to be confined during the Cretaceous but diversified during the Miocene and are still alive today
Thresher Shark
Paranomotodon angustidens (Cope)
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Anterior tooth
a. Lingual view  b. Labial view
Lateral tooth
a. Lingual view  b. Labial view  c. Drawing
Outline of Thresher Shark
Anterior tooth
a. Lingual view  b. Labial view