Bonnet Hammerhead
Sphyrna tiburoSummary 1
The bonnethead shark or shovelhead, Sphyrna tiburo, is a member of the hammerhead shark genus Sphyrna. The Greek word sphyrna translates as hammer, referring to the shape of this shark's head - tiburo is the Taino word for shark.
Description 2
Common names: bonnethead (English), shark (English), tiburón (Espanol), cabeza (Espanol), cornuda (Espanol)
Sphyrna tiburo (Linnaeus, 1758)
Bonnethead, Common bonnethead shark
A small hammerhead shark with a very narrow, rounded shovel-shaped head, without the prominent lateral-blade extensions of other hammerheads; width of head 18-25% (usually < 21%) of TL; front margin of head broadly convex and without indentations; length before mouth about 40% of head width; front teeth blade-like, with 1 short, stout point, lower teeth straight, upper teeth oblique, deeply notched on rear side; enlarged keeled molariform teeth at back of jaws; first dorsal fin moderately large and erect, its rear margin concave; second dorsal fin base about half length of anal fin base; origin of second dorsal fin above middle of anal fin; anal fin rear edge shallowly concave; transverse pit above tail base crescent shaped, a pit below tail base; tail fin strongly asymmetrical, notched under tip of top lobe, large lower lobe.
Grey or grey brown on back and sides, whitish below; often small dark spots on back.
Maximum size about 150 cm, 10.8kg; size at birth 35-40 cm.
A common inshore hammerhead ranging into shallow estuaries.
From the intertidal zone to at least 80 m depth.
Western Atlantic and eastern Pacific (Southern California to Peru, Cocos and the Revillagigedos Islands.
Distribution 3
Found on both the East and West coast of North and South America. In the western Atlantic, they are found from southern Brazil to North Carolina, straying to Massachusetts Bay and Nantucket Sound.
Physical description 4
The characteristic shovel- or bonnet-shaped head makes this hammerhead the easiest to identify. Body moderately compact; head flattened, spade-shaped front margin of head not lobed without nasal grooves, the anterior margin of the head is evenly rounded between the eyes; mouth arched; mouth corners posterior to oculonarial expansion. The frontal teeth have erect, smooth-edged cusps, while subsequent teeth have oblique cusps; the outermost teeth of the lower jaw are modified into flat crushers. First dorsal fin high, originating slightly posterior to base of pectoral fin; second dorsal with rear lobe not well developed, higher and shorter than anal one; eyes separated from nasal grooves by a distance of 1.5 times diameter of eye. Some are dark brown in the lateral dorsal region, lighter in ventral region while others are gray or greensih gray above and paler below. Average size is 70-100 cm (28-39 in.) Maximum size is about 110 cm (43 in.) These are the smallest of family Sphyrnidae (Cortes and Parsons,1996).
Range mass: 3 to 4 kg.
Average mass: 0.0035 kg.
Size 5
Maximum size: 1500 mm TL
Diagnostic description 6
Front of head semicircular in outline. No other hammerhead has front of head in semicircle. (Ref. 26938).
I dnature guides 7
Identification key for shorefishes of the tropical eastern Pacific
Habitat 8
nektonic
Life cycle 9
Viviparous, placental (Ref. 50449), with 6 to 9 young per litter. Size at birth about 35 to 40 cm.
Reproduction 10
S. tiburo reproduces sexually and is viviparous. Maturity is reached at about 75 cm (30 in). The pups are born in late summer and early fall and measure 30-32 cm (12-13 in) at birth and approximately 172 g. Usually eight to twelve pups are produced in each litter.
Survivorship for young individuals, especially newborn pups, may be affected by size-selective predation.
Geographic variation does seem to have an effect on the survival of the pups, as well as the weight and size. In Florida Bay and Tampa Bay there was a study of two populations of bonnethead sharks. Size at maturation, age at maturation, time of fertilization, rate of embryonic development, size at birth, the energetic investment in producing offspring, gestation period, and the incidence of fertility were found to differ between these population. Food limitations and seasonal differences may play a role in these differences (Castro, 1987).
Link to Access Genomic Data 11
http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=7824&lvl=0
Sources and Credits
- Adapted by matbio from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Sphyrna_tiburo
- Adapted by matbio from a work by (c) Shorefishes of the tropical eastern Pacific online information system. www.stri.org/sftep, some rights reserved (CC BY-NC), http://eol.org/data_objects/26219495
- Adapted by matbio from a work by (c) WoRMS for SMEBD, some rights reserved (CC BY), http://eol.org/data_objects/28471444
- Adapted by matbio from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/18673975
- Adapted by matbio from a work by (c) FishWise Professional, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/24198905
- Adapted by matbio from a work by (c) FishBase, some rights reserved (CC BY-NC), http://eol.org/data_objects/20846783
- Adapted by matbio from a work by (c) Discover Life and original sources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11586753
- Adapted by matbio from a work by (c) WoRMS for SMEBD, some rights reserved (CC BY), http://eol.org/data_objects/28475375
- Adapted by matbio from a work by (c) FishBase, some rights reserved (CC BY-NC), http://eol.org/data_objects/20846786
- Adapted by matbio from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/18673976
- (c) matbio, all rights reserved
