Hammerheads see three-sixty above and below at once
The cephalofoil spreads eyes to the ends of a T-shaped head, granting continuous vertical coverage, deeper binocular vision, and a wider electroreceptor antenna of Lorenzini pores. Great hammerheads average four metres and 230 kilograms; bonnetheads stay near 1.5 metres—and in 2007 one reproduced without a male.
Most species sit in Sphyrna; the winghead alone is Eusphyra and, by mitochondrial trees, sister to the rest, implying ancestral hammers were already large. Closest relatives are requiem sharks; combined molecular and fossil work pushes origins to Cretaceous or Paleocene, with clear family fossils by the Eocene (earlier DNA guessed a Miocene start near twenty million years ago). Daytime schools can break into solitary night hunts across warm shelves worldwide.
Manoeuvre myths once credited the hammer; vertebral design matters more for tight turns, though the foil still adds lift. Mouths sit small and crescent beneath, ideal for pinning rays and flounders to sand before the bite. Diets span fish, squid, crustaceans, and fellow sharks; great hammerheads may eat other hammerheads. Bonnetheads can fill half a stomach with seagrass and partly digest it—an early claim of shark omnivory later joined by whale sharks. Viviparous moms nourish pups via a yolk-sac placenta; litters run about 12–15, or 20–40 in greats, then no parental care.
Since 1580 the International Shark Attack File lists seventeen unprovoked Sphyrna bites and zero human deaths. IUCN in 2008 called great and scalloped hammerheads endangered and smalleye vulnerable, driven by fin demand. FAO capture tallies rose from 75 metric tons in 1990 to 6,313 by 2010; roughly 375,000 great hammerheads may enter the fin trade yearly. CITES Appendix II listed hammerheads in March 2013. Public aquaria rarely keep large species long; bonnetheads breed more readily behind glass.
Source: Hammerhead shark
