2016 SELACHII from “World of Evolution” Series; 1 oz Antiqued Silver Coin with Real Shark Tooth Fossil; 1000 Francs Burkina Faso

Description

Metal                    Silver

Purity                   0.999

Weight                 31,1 g (1 Troy oz)

Diameter              44 mm

Attributes             Real Shark Tooth Fossil, Antique Finish

Mintage                500

Presentation Box and CoA Included

The second coin in the “World of Evolution” series.

Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii) and are the sister group to the rays. Sharks have diversified into over 500 species. They range in size from the small dwarf lantern shark (Etmopterus perryi), a deep sea species of only 17 centimeters in length, to the whale shark (Rhincodon typus), the largest fish in the world, which reaches approximately 12 meters in length.

Sharks are found in all seas and are common to depths of 2,000 metres. They generally do not live in freshwater although there are a few known exceptions, such as the bull shark and the river shark, which can survive and be found in both seawater and freshwater. Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth.

Shark teeth are embedded in the gums rather than directly affixed to the jaw, and are constantly replaced throughout life. Multiple rows of replacement teeth grow in a groove on the inside of the jaw and steadily move forward in comparison to a conveyor belt; some sharks lose 30,000 or more teeth in their lifetime. The rate of tooth replacement varies from once every 8 to 10 days to several months. In most species, teeth are replaced one at a time as opposed to the simultaneous replacement of an entire row, which is observed in the cookiecutter shark.

Because of the nature of a shark’s skeleton, made from a cartilaginous material instead of bone, fossils are overwhelmingly teeth, helped by the almost production-line way they are grown and discarded.