The Cow Nosed Rays

Brachyrhizodus wichitaensis (Roemer)
Rhombodus laevis (Cappetta & Case)

Age  Cretaceous - Occurrence  Very common
 

Two species of Cow nosed rays can be found in NJ, Brachyrhizodus wichitaensis and Rhombodus laevis. Both rays have flat crusher teeth that were arranged into a tooth battery with an enamel covered crushing surface. Of the two species Brachyrhizodus wichitaensis is the more common of the two, although this may be due to size. The teeth of Rhombodus laevis are small, usually under ¼ of an inch and can easily fall through the standard ¼ inch mesh screen. Not as common, the dermal scutes and vertebra of these rays can also be found. Both species became extinct by the end of the Cretaceous period.

Left— Brachyrhizodus wichitaensis
Right— Rhombodus laevis
Monmouth County, NJ
Scale 1 inch

Brachyrhizodus wichitaensis, the larger of the two species has a hexagonal shape.
The nutrient groves or lines in the root varies depending on tooth position.
 

Rhombodus laevis is a small tooth, usually under 1/4 inch and has a distinct
4 sided shape with a very deep nutrient grove.
Scale 1 inch
 

Variations in tooth size and shape can be attributed to the
position of the tooth in the jaw.
Brachyrhizodus wichitaensis
 

The crowns on Rhombodus laevis seem very subject to
in-vivo wear. In general, the crowns on most ray teeth will show
 some degree of wear.
 

The vertebrae of the rays have an oval shape. These can range in
size from 1/4 inch to well over an inch.

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