(Sphyrna zygaena) -- Although they prefer to remain in the open ocean, the Common Hammerhead is one of the largest sharks in the Delaware-Chesapeake Bay area and is a familiar sight for anglers along the coast in summer.
With an average size of 2 to 4 feet, hammerheads can grow to as long as 6 to 13 feet.

  The hammerhead is easily recognizable since it is one of the strangest looking creatures in the water. Peculiar projections on both sides of the head give it the appearance of a flattened hammer. The shark's eyes and nostrils are at the lateral tips of the extensions. During the days of heavy commercial shark fishing, hammerheads were in demand for use in fish meal, liver oil and leather products.

  Its curious head has lateral projections resembling the crossbar of a T, and its eyes and ears are located in the outer tips of the projections. It has been suggested that the extension of the head in the plane of the pectoral fins may give the fish increased lift, but there is no evidence that hammerheads are better swimmers than other sharks. Found in inshore, brackish water, hammerheads are both predators and scavengers.

  They feed on a variety of fishes including skates, rays, and other hammerheads, and large hammerheads have been known to attack and eat humans without provocation.Geneticist Andrew Martin used mtDNA sequence data to explore the origins and pattern of hammer development in seven species (including two sub-species) of hammerhead shark. Martin's results supported the common-sense idea that the hammerheads constitute a monophyletic group (sharing a common ancestor) derived from the carcharhinids, but also revealed some surprises. The molecular data strongly suggest that the Winghead Shark - not the Bonnethead - was the first hammerhead to diverge from the group's common ancestor and that the bonnethead was, in fact, the most recent hammerhead to appear. Furthermore, the same data suggest that the relative size of the hammer fluctuated slightly between wider and narrower in closely-related species rather than showing any clear trend.
  The great hammerhead is a fierce predator with a good sense of smell that helps it find its prey. The great hammerhead eats fish, including rays, and other sharks, squid, octopuses, and crustaceans. The great hammerhead has been known to be cannibalistic.