Genus Thunnus (South , 1845)
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.
Thunnus sp. hypural plate
Monmouth County, NJ
The hypural plates are considered part of the spine. You can see
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.
Fierstine HL, Walters V. 1968. Studies in locomotion and anatomy of
scombroid fishes. Los Angeles: Anderson, Ritchie & Simon.
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