Tuna

  Family Scombridae
Genus Thunnus (South , 1845)
Thunnus sp.

Age - Paleocene to present - Occurrence - Uncommon

Thunnus is a genus of bony fish from the Scombridae or Mackerel family. To my knowledge the fossil remains found in New Jersey of this
well know fish are limited to the hypural plates located at the end of the spine. These plates give a firm anchoring point for the strong muscle tendons of this high speed animal.
  Modern Tunas are negatively buoyant and must swim continuously to avoid sinking. One of the most striking features of the scombrids is that some groups are endothermic (warm-blooded), The tuna's ability to maintain body temperature has definite advantages over other fish by not limiting it's range according to water temperature.

Plate 1
Thunnus sp. hypural plate
Monmouth County, NJ
 

 Plate 2
The hypural plates are considered part of the spine. You can see where this
would connect to the other vertebrae in the image on the right.

A bit difficult to find a complete one, definitely an unusual fossil.

Monmouth Country, NJ.

 

References

Fierstine HL, Walters V. 1968. Studies in locomotion and anatomy of scombroid fishes. Los Angeles: Anderson, Ritchie & Simon.

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