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This was the first common style of shark tooth, present in the Devonian, four hundred million years ago. [10] Sharks with needle-like teeth commonly feed on small to medium-sized fish, sometimes including small sharks.
Each tooth is small and needle-like, with a narrow central cusp and smooth to minutely serrated edges. The five pairs of gill slits are long, measuring about half the length of the dorsal fin base. [2] The first dorsal fin is high and triangular with a pointed apex, originating forward of the free rear tips of the pectoral fins.
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 ...
This is a typical Cladodont tooth, of a shark called Glikmanius. Cladodont (from Latin cladus, meaning branch and Greek Odon, meaning tooth) is the term for a common category of early Devonian shark known primarily for its "multi-cusped" tooth consisting of one long blade surrounded by many short, fork-like tines, designed to catch food that was swallowed whole, instead of being used to saw ...
The youngest and first tooth at the center of the spiral, referred to as the "juvenile tooth arch", is hooked, but all other teeth are generally triangular in shape, laterally compressed and often serrated. [7] Tooth size increases away from the center of the spiral (abaxial), with the largest teeth possibly exceeding 10 cm (3.9 in) in length.
In the international system of notation two numbers are used to identify the tooth. The first number identifies the quadrant of the mouth. The second number identifies the tooth relative to the midline of the arch. The right permanent maxillary first molar is known as "16". The left permanent maxillary first molar is known as "26".
Shark teeth are strong and made of enamel. Many sharks have 3 rows of teeth. These teeth are embedded in the gums, not the jaw. [10] Sharks are born with teeth that are constantly being replaced. Teeth are replaced every two weeks, approximately. [10] The shape of the teeth determine the diet of the shark.
However, sharks continuously produce new teeth throughout their lives [3] [4] [5] via a drastically different mechanism. Shark teeth form from modified scales near the tongue and move outward on the jaw in rows until they are eventually dislodged. [6] Their scales, called dermal denticles, and teeth are homologous organs. [7]