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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.
Shark migration patterns may be even more complex than in birds, with many sharks covering entire ocean basins. Sharks can be highly social, remaining in large schools. Sometimes more than 100 scalloped hammerheads congregate around seamounts and islands, e.g., in the Gulf of California. [39] Cross-species social hierarchies exist.
While tiger sharks, which are typically both a few feet smaller and have a leaner, less heavy body structure than white sharks, have been confirmed to reach at least 5.5 m (18 ft) in the length, an unverified specimen was reported to have measured 7.4 m (24 ft) in length and weighed 3,110 kg (6,860 lb), more than two times heavier than the ...
A 2009 study tagged 25 sharks off the coast of Cape Cod, Massachusetts, and indicated at least some migrate south in the winter. Remaining at depths between 200 and 1,000 metres (660 and 3,280 ft) for many weeks, the tagged sharks crossed the equator to reach Brazil. One individual spent a month near the mouth of the Amazon River. They may ...
Greenland sharks have also been found with remains of moose, polar bear, horse, and reindeer (in one case an entire reindeer body) in their stomachs. [26] [27] [28] The Greenland shark is known to be a scavenger and is attracted by the smell of rotting meat in the water. The sharks have frequently been observed gathering around fishing boats. [26]
In the years after World War I, Sergeant Stubby met several U.S. presidents and received many awards. He died in 1926, and his taxidermied corpse is held in the National Museum of American History ...
Image credits: 1stPeter3-15 #21. The first public game of basketball was played the same week and less than 100 miles away from the last American vampire hunt.
They were smaller than most placoderms, usually under 20 centimetres. Spiny sharks did not diversify as much as placoderms, but survived much longer into the Early Permian about 290 million years ago. [73] The original selective advantage offered by the jaw may not be related to feeding, but rather to increased respiration efficiency. [74]