THE SHARKS

The Extinct Thresher
Paranomotodon angustidens (Cope)

Age - Cretaceous  Commonality - Less common

The extinct thresher (Paranomotodon angustidens) saw worldwide distribution during the Cretaceous period. Fossil records of Paranomotodon angustidens are confined to the Cretaceous sediments with Alopias latidens, the ancestors of today's thresher, appearing during the Miocene. The teeth of the thresher are small, averaging about ½ inch and can be fairly common in some locations. The root has a “U” shape appearance with a short nutrient groove, this nutrient grove is often worn away by stream action. A very distinct feature of Paranomotodon angustidens is the concave basal root margin seen on the labial side of the tooth. The shoulders of the crown have a block like appearance which I have seen described as “weak lateral cusplets” or “vestigial cusplets”.  The crown is erect on anterior teeth and distally curved on laterals.
 

Lateral and anterior teeth of Paranomotodon angustidens.
The anterior tooth on the right is just under 1/2 inch.
Monmouth County, NJ
 

The block like shoulders or weak lateral cusplets. On the right the
concave basal root margin can be seen.

The short nutrient groove on an anterior tooth.
The roots of these teeth seem especially prone to stream wear and
the nutrient grove may not be present on some stream worn specimens.

Identified as a pristine first anterior tooth by Jerry Case.

This specimen has been donated to the University de Montpellier
 in France.
 

Paranomotodon angustidens.
 

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