Friday, August 3, 2007

Miocene Sharks Teeth of Calvert County

The sharks' teeth collected along the shore of the Chesapeake Bay between Chesapeake Beach and Calvert Cliffs in Calvert County are records of a far distant past when the climate, geography, and living creatures in this area were quite different from those of today. Back in the Miocene Epoch, about 17 million years ago, the sharks that bore these teeth lived in the warm, shallow sea that covered southern Maryland.

The present-day configuration of the Chesapeake Bay emerged, with the deposits of the Calvert Cliffs that were once sea bottom now standing 100 ft. above the water line. Fossil remains of animals from that ancient sea floor are now exposed as wind and water erode the cliffs, and represent the most extensive assemblage of this period in the Eastern United States.

The teeth of extinct sharks most commonly found here belong to the following species: Galeocerdo contortus, and G. triqueter (Tiger Sharks), Hemipristis serra (Requiem Shark), Oxyrhina desorii (Mackerel Shark), Sphyrma prisca (Hammer-head Shark), and the Sand Shark, Odontaspis elegans. Teeth of the spectacular giant White Shark, Carcharondon megalodon, are found here too, but are rare.

From the great number of teeth that have been and are still found here, initially one wonders how so many sharks could have lived in a relatively restricted area.

There are several reasons for this abundance. First, sharks have an unlimited supply of teeth. No cavities, permanently missing teeth, or tooth aches for them! Shark teeth are not set firmly in the jaws, but in the gums, where they occur in layered rows. If a tooth is lost, it is gone but briefly, for another from the reserve layer moves forward to take its place. Also, recent studies indicate that the young of one common modern shark replace their upper teeth every 7.2 days, and the lower ones every 8.2 days! It is possible that this may have held true in fossil sharks.

Check out our Chesapeake bay sharks teeth fossil jewelry and get a little history of your own.

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