SkaTES, RAYS and FISH

 

RATFISH
Ischyodus (Case)

Age  Cretaceous - Occurrence  Less common

 The Ratfish, Ischyodus is an extinct genus of cartilaginous fish (skeletons made of cartilage rather than bone) thought to be the evolutionary link between sharks and bony fish. The ratfish was widespread and fairly common during the Cretaceous period. Fragments of the mouth plate are somewhat common, with most specimens being in the 1/2 to 1 inch range. Larger pieces are a little harder to come by. The light colored ridges and/or dots are the distinctive markings of a Ratfish mouth plate. While scarce, the cephalic claspers of the ratfish can also be found.
Note: The Chondrichthyes or cartilaginous fishes are divided into two subclasses. The Elasmobranchii (sharks, rays and skates) and Holocephali (chimaera). The ratfish is actually a member of the later.

The bony jaw plates, used for crushing, are marked with rows of tabular,
 spongy looking channels called tritors.
Scale 1 inch
Monmouth County, NJ

An assortment of fragments, the ones on the left are typical finds.

A complete ratfish mandible. Measuring a little under 3 inches this is
a rather unique find for Monmouth County.  
 

A close up of the tritors.
 

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