archman:
Well, they're not bonnetheads. Sphyrna tiburo isn't an open water species, and anyways they don't get much longer than a meter.
Most likely Great Hammerheads or Scalloped Hammerheads
SCALLOPED HAMMERHEAD
Order - Carcharhiniformes
Family - Sphyrnidae
Genus - Sphyrna
Species - lewini
GREAT HAMMERHEAD
Order - Carcharhiniformes
Family - Sphyrnidae
Genus - Sphyrna
Species - mokarran
Taxonomy
The great hammerhead was originally described as Zygaena mokarran by German naturalist Eduard Rüppell in 1837, however he changed this name to the currently valid Sphyrna mokarran later that same year. The name Sphyrna translates from Greek to the English language "hammer", referring to the hammer-shaped head of this species. Synonyms used in past scientific literature include Sphyrna tudes Valenciennes 1822, Zygaena dissimilis Murray 1887 and Sphyrna ligo Fraser-Brunner 1950.
There are approximately 10 related species of hammerheads throughout tropical and temperate regions including the bonnethead (Sphyrna tiburo), great hammerhead (Sphyrna mokarran), and smooth hammerhead (Sphyrna zygaena).
Common Names
English language common names include great hammerhead, great hammerhead shark, and squat-headed hammerhead shark. Other common names are abu garn (Arabic), akran (Arabic), cação-martelo (Portuguese), cachona (Spanish), cachona grande (Spanish), cambeva (Portuguese), cawar (Somali), cornuda de ley (Spanish), cornuda gigante (Spanish), glowomlot olbrzymi (Polish), grand requin marteau (French), grande squalo martello (Italian), großer hammerhai (German), grote hamerhaai (Dutch), hira-shumokuzame (Japanese), isovasarahai (Finnish), jarjur (Arabic), martelo (Portuguese), martillo (Spanish), megalozygena (Greek), nami-shumokuzame (Japanese), papa mbingusi (Swahili), peix martelo (Portuguese), : pesce martello maggiore (Italian), pez martillo (Spanish), requin marteau (French), tollo cruz (Spanish), yu parang (Malay), and yu tukul (Malay).
Geographical Distribution
Circumtropical in distribution, the great hammerhead is found in coastal warm temperate and tropical waters within 40°N - 37°S latitude. In the western Atlantic Ocean, it ranges from North Carolina (US) south to Uruguay, including the Gulf of Mexico and Caribbean regions, while in the eastern Atlantic Ocean, this species ranges from Morocco to Senegal, including the Mediterranean Sea. Distribution of the great hammerhead includes the Indian Ocean and the Indo-Pacific region from Ryukyu Island to New Caledonia and French Polynesia. The eastern Pacific range is from southern Baja, California (US) through Mexico, south to Peru. The great hammerhead is considered a highly migratory species within Annex I of the 1982 Convention on the Law of the Sea.
Distinctive Features
The great hammerhead is a very large shark with the characteristic hammer-shaped head from which it gets its common name. The font margin of the head is nearly straight with a shallow notch in the center in adult great hammerheads, distinguishing it from the smooth hammerhead and scalloped hammerhead. The first dorsal fin is very tall with a pointed tip and strongly falcate in shape while the second dorsal is also high with a strongly concave rear margin. The origin of the first dorsal fin is opposite or slightly behind the pectoral fin axil with the free rear tip falling short to above the origin of the pelvic fins. The rear margins of the pelvic fins are concave and falcate in shape, not seen in scalloped hammerhead (S. lewini). The posterior edge of the anal fin is deeply notched.
Just like the picture...Greathammerhead (on the left)
Larger sharks such as these schooling scalloped hammerheads (Sphyrna lewini: on the right) prey on small lemon sharks.
Scalloped Hammerhead adults occur singly, in pairs, and in small schools while young scalloped hammerhead sharks live in large schools. In some locations, schools of small hammerheads have been observed migrating toward the poles during the summer months while permanent resident populations exist in other areas including the
East China Sea. It is thought that male and female scalloped hammerheads may segregate during certain times of their life history. In the Gulf of California (US), aggregations of predominantly females ranging from immature to adult have been observed around seamounts and islands displaying a wide range of behaviors. These behaviors have ranged from headshaking, corkscrew swimming, and knocking into other hammerheads with their snouts. Although the function of such schooling behaviors is unknown, it is suspected that some of these behaviors may be displays of aggression or courtship.
