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A hammerhead shark is a type of shark that has been named after the particularly unusual and distinctive shape of its head. The head of these sharks extends outward to both sides in two fairly long, flat extensions with one eye located at either end of the extension. This shape lends the head of these sharks a somewhat hammer-like appearance when seen from above. There are several different species of hammerhead shark and they have a number of unique and peculiar attributes beyond the unusual shape of their heads.
Mostly belonging to the family Sphyrnidae and the genus Sphyrna, a hammerhead shark is a cartilaginous fish just like other sharks, meaning its skeleton is primarily made of cartilage rather than bone. The reason and usefulness of the unusual shape of their heads has been speculated about and theorized by many different scientists for a great deal of time. One of the strongest theories for a long time was that the shape of the head allowed hammerhead sharks to be more maneuverable and turn more quickly in water.
More recently, however, it is believed that the particular vertebrae the hammerhead shark has allow it to make tight the observed physical turns. There is strong evidence to indicate the shape of the shark’s head is more about perception, as the wide separation of its eyes allows greater binocular vision than many other sharks. A hammerhead shark can effectively see above and below itself while swimming, as well as seeing in front of itself and to each side. The wider separation of its nostrils also allows it to be more sensitive to its environment while finding prey.
A hammerhead shark will usually hunt along the bottom of the ocean and has a relatively small mouth compared to other sharks. Though often a solitary predator at night, during the day they have been observed traveling in schools of more than 100 sharks. They typically feed on other sharks, squid, octopus, sting rays, and even their own young.
Hammerhead sharks give live birth, and embryos are typically fed through a yolk sac initially, which becomes a “pseudoplacenta” toward the end of gestation, allowing nutrients to pass from the mother to the developing baby. There has even been an observed instance of asexual reproduction in one type of hammerhead shark, in which a female was able to form a zygote without the need of male sperm. The skin of a hammerhead shark is able to receive a sun tan, which is quite unusual and can occur if the shark spends excessive time in shallow waters.