Author: (Valenciennes, 1822)
Field Marks:
A small hammerhead with a moderately broad, anteriorly arched, mallet-shaped head with medial and lateral indentations on its anterior edge and transverse posterior margins, strong prenarial grooves present on front edge of head, snout rather short and less than 1/3 of head width, moderately large, broadly arched mouth, free rear tip of first dorsal fin over pelvic insertions, posterior margin of anal fin moderately concave and not deeply notched.
Diagnostic Features:
Expanded prebranchial head hammer-or axe-shaped and very wide but longitudinally fairly long, its width 28 to 32% of total length (mostly above 28%); distance from tip of snout to rear insertions of posterior margins of expanded blades about 2/5 of head width; anterior margin of head broadly arched with prominent medial and lateral indentations; posterior margins of head wide, transverse, and generally broader than mouth width; well-developed prenarial grooves present anteromedial to nostrils; preoral snout about 1/4 to slightly less than 1/3 of head width; rear ends of eyes slightly anterior to upper symphysis of mouth; mouth rather narrowly arched; anterior teeth with moderately long, slender, smooth or weakly serrated cusps, posterior teeth mostly cuspidate and not keeled and molariform. First dorsal slightly falcate, its origin slightly behind pectoral insertions, its free rear tip about over pelvic origins; second dorsal fin fairly high, less than anal height, with a shallowly or moderately concave posterior margin; its inner margin moderately long, but less than twice fin height, and ending well in front of upper caudal origin; pelvic fins not falcate, with straight or slightly concave posterior margins; anal fin larger than second dorsal fin and rather long, its base 7.5 to 9.9% of total length; its origin well ahead of second dorsal origin, its posterior margin shallowly to moderately concave. Total vertebral centra 195 to 202. A small hammerhead, to 1.5 m. Colour grey-brown above, light below, fins without markings.
Geographical Distribution:
Western Atlantic: Venezuela to Uruguay. Records of this species from off Mississippi in the northern Gulf of Mexico (Gilbert, 1967a) were probably incorrect (Robins et al., 1980). The original 3 Mediterranean record of this shark by Valenciennes (1822) may also be incorrect and based on S. couardi (Cadenat and Blache, 1981; see remarks below).
Habitat and Biology:
A little-known inshore shark of the continental shelf, found down to at least 12m depth. Viviparous, with a yolk-sac placenta; number of young probably 6 to 9 per litter.
Feeds on small bony fishes, including sea catfish and grunts, but also 4 newborn scalloped hammerheads (S. lewini), swimming crabs, squid, and shrimp.
Size:
Maximum about 150 cm, adult males 110 to 134 cm, adult females 120 to 148 cm; size at birth about 30 cm.
Interest to Fisheries:
A locally abundant species taken in coastal fisheries but with details of gear and utilization not reported. Reported very common off the Guianas in the western Atlantic but uncommon elsewhere there and rare in the eastern Atlantic and Mediterranean.
Remarks:
The name Sphyrna tudes was long applied to the great hammerhead (see Bigelow and Schroeder, 1948), while Springer (1944) described ff bigelowi for the present species. However, Tortonese (1950a) and Gilbert (1967) noted that the specimen illustrated by Valenciennes (1822) as S. tudes from Nice, France and another late embryo mentioned by him from Cayenne, French Guiana (the two remaining syntypes in the Museum National d'Histoire Naturelle, Paris) are conspecific with Springer's material of S. bigelowi, and that the next available name, S. mokarran, must be used for the great hammerhead. Gilbert (1967) suggested that the third, lost syntype of S. tudes from Coromandel, India was actually based on the great hammerhead, but in its absence he considered S. tudes as the proper name for this species, the smalleyed hammerhead, and considered S. bigelowi a junior synonym (following Tortonese, 1950a). Gilbert took the step of naming MNHN 1049 from Nice, France, as the lectotype of S. tudes and MNHN 1019 from Cayenne as its paralectotype to stabilize S. tudes but he may have achieved the opposite effect. Cadenat and Blache (1981), after examining the two Paris specimens, suggested that these in fact represented two species, the Cayenne specimen being conspecific with material of S. bigelowi Springer, but the designated lectotype from Nice is based on a fetus of S. couardi Cadenat, 1950! If this is correct and Gilbert's lectotype designation is followed, S. tudes must be considered a senior synonym of S. couardi and used for the whitefinned hammerhead, while S. bigelowi must be revived for the smalleyed hammerhead. This would not serve nomenclatorial stability, but an alternate solution, rejection of Gilbert's lectotype designation and redesignation of the Cayenne specimen as the lectotype of this species, would allow the retention of the present nomenclature: S. tudes for the western Atlantic smalleyed hammerhead and S. couardi for the eastern Atlantic whitefinned hammerhead. However, this would require a petition to the International Commission on Zoological Nomenclature and an Opinion by that body. The writer has not seen the syntypes in question and cannot confirm Cadenat and Blache's observations at present, so for this account Gilbert's arrangement is retained as a temporary expedient. The identity of the Nice specimen with S. couardi would explain why no specimens of the smalleyed hammerhead have been collected in the eastern Atlantic or Mediterranean Sea.
Type material:
Lectotype: Museum National d'Histoire Naturelle, Paris, MNHN 1049, 346 mm immature female, designated by Gilbert (1967:65). Syntypes in Museum National d'Histoire Naturelle, Paris, MNHN 1019, from Cayenne, French Guiana, MNHN 1049, a 346 mm female from off Nice, France, and a third specimen, apparently lost, from Coromandel, India. MNHN 1049 was selected as a lectotype by Gilbert (1967; see remarks below). Type Locality: Nice, France, Mediterranean Sea.