And that has a big effect on how these animals move. In the majority of sharks, the pectoral fins are longer than the first dorsal-but for great hammerheads, the opposite is true. Sharks also have a pair of pectoral fins, located on either side of the body just behind the head, which most species use to steer and generate lift. Probably the most recognizable is the first dorsal fin it typically acts like a sailboat keel, helping the shark stay balanced while it swims. GREAT HAMMERHEADS LIKE TO SWIM SIDEWAYS.Ī typical shark has eight fins on its body. Although the researchers didn’t find a difference in sensitivity to the electric fields between a hammerhead and a cone-nosed sandbar shark, the hammerhead was able to search a larger area, which the researchers say would “increase the probability of prey-encounter.” The researchers also noted that the hammerhead was more maneuverable than the sandbar shark. A 2002 experiment seemingly lent credence to this notion. Hammerheads, like all other sharks, have sensory organs that can detect the electric fields of prey in the water some scientists hypothesize that the broad cephalofoils allow hammerheads to have more of these organs-therefore allowing them to better sense prey. These sharks' broad, flat, hammer-shaped heads are called cephalofoils, and no other creature in the world has a head quite like it. THEIR HEADS MAY GIVE THEM A HUNTING EDGE. They also argued that today’s modestly-sized bonnethead and winghead sharks independently evolved from big ancestors. What did the earliest hammerheads look like? According to the researchers, these were probably large-bodied animals. The fossil record tells us sharks have existed for at least 420 million years-so if the University of Colorado team is correct, hammerheads are relative newcomers on the world stage. The molecular evidence suggested that the hammerheads started to diversify around 20 million years ago. In 2010, geneticists at the University of Colorado, Boulder compared DNA samples from eight hammerhead species in an attempt to map out the family’s evolutionary history. IT LOOKS LIKE THEY EVOLVED SOMEWHAT RECENTLY. Three hammerhead species have a high risk of extinction: the great hammerhead, which is threatened by the shark fin trade and bycatch (unwanted fish captured as a byproduct of commercial fishing) the winghead ( Eusphyra blochii), whose population is believed to have declined 50 percent in 42 years from overfishing and net entanglement and the scalloped hammerhead ( Sphyrna lewini), which, in 2014, became the first shark to ever receive protection from the U.S. Hammerheads also vary in terms of overall size: The smaller species max out at 3 to 5 feet in length, while the biggest is the great hammerhead ( Sphyrna mokarran), which can be up to 18 feet long and weigh over 1000 pounds (with 10 to 13 feet and 500 pounds being closer to average). Keen-eyed observers can tell most of these guys apart by the slight differences in their skull shapes. Nine belong to the genus Sphyrna (Greek for "hammer"), while the other-an oddball called the winghead shark-is the sole member of its own genus, Eusphyra. Įxperts have identified 10 living shark species in the hammerhead family (although it’s possible that even more exist). These fish are diverse, they’re weird, and someday they might change the way we fight skin cancer. Is there any fish in the world that casts a more distinctive shadow? Divers have little trouble recognizing a hammerhead when they see one.
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