No Such Thing as a “Typical Shark”—Shark Diversity, Part 2

sharkdiversity2

Pajama, Bullhead Zebra, Portjackson

Here’s some more ways that sharks are diverse:

Size
Sharks come in a wide range of sizes. Dwarf Dogfish are the smallest, reaching a max length of only 8 inches. Whale sharks are the largest. The biggest one actually measured was 42 feet, though there are estimates that they reach up to 60 feet. While there are several other sharks that grow to be close to or more than 20 feet long, most reach more moderate  lengths. About half of known shark species are under 3 feet long, and eighty percent don’t exceed 9 feet.

Body Shape
Pelagic sharks have streamlined, torpedo shaped bodies. Deep-sea sharks often have stout midsections with tapered ends. Bottom dwelling species are flattened. An extreme example of a flattened shark is the Angel shark, which resemble rays with their flat bodies and extra wide side fins. They hide themselves under sand to surprise their prey.

Tails
Pelagic sharks have symmetrical or slightly asymmetrical tails to facilitate fast swimming speeds, while the tails of the more sluggish deep-sea and bottom dwellers usually have an elongated upper lobe and a small or non-existent lower lobe. Half of the length of a Thresher shark, which can grow to be up to 20 feet long, is the upper lobe of its tail. Since Thresher sharks occasionally get hooked on baited fishing lines by the end of their tail, it’s assumed that they whip their tails at fish to stun or kill them.

Heads and Snouts
There are a few sharks with unusual heads or snouts. The wide head of Hammerheads provides them with extra lift and spreads out their ampullae of Lorenzini—small pores that can sense electric emissions, such as those given  off by a beating heart—over a greater surface area. They also use their heads to pin rays to the seafloor, then swivel around to take bites out of the ray’s wings. Goblin sharks have elongated, flattened, blade-like snouts that also serve to increase the surface area of their electroreceptors. Sawsharks have elongated snouts with teeth embedded along the edges like a saw, which they use to dig up and kill their prey.

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