Author: Springer, 1940
Field Marks:
A small hammerhead with a moderately broad, anteriorly arched, mallet-shaped head with weak medial and lateral indentations on its anterior edge and transverse posterior margins, no prenarial grooves, snout rather short and about 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 nearly straight.
Diagnostic Features:
Expanded prebranchial head malletshaped and moderately wide but longitudinally expanded also, its width 22 to 33% of total length (mostly above 23%); distance from tip of snout to rear insertions of posterior margins of expanded blades half the width of head or more; anterior margin of head broadly arched, with weak medial and lateral indentations; posterior margins of head narrow, angled transversely, and as broad or somewhat narrower than mouth width; prenarial grooves absent or hardly developed; preoral snout about 1/3 to 2/5 of head width; rear ends of eyes somewhat anterior to upper symphysis of mouth; mouth rather broadly arched; anterior teeth with long slender, smooth-edged cusps, posterior teeth mostly cuspidate and not keeled and molariform. First dorsal moderately falcate, its origin over inner margins of pectoral fins and near their insertions, its free rear tip over pelvic origins; second dorsal fin moderately high, equal to or less than anal height, with a straight to moderately concave posterior margin; its inner margin short, less than twice fin height, and ending well in front to slightly 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, base 7.2 to 9% of total length; its origin well ahead of second dorsal origin, its posterior margin shallowly to moderately concave. Total vertebral centra 101 to 196. A small hammerhead, to 1.5 m. Colour grey-brown above, light below, fins unmarked.
Geographical Distribution:
Western Atlantic: Panama to southern Brazil. Eastern Pacific: Gulf of California to Ecuador and probably northern Peru.
Habitat and Biology:
A little-known, inshore tropical hammerhead of the American continental shelves.
Size:
Maximum about 150 cm, adult male 90 cm, adult females 100 to 133 cm, adolescent female 83 cm; size at birth 34 cm or less.
Interest to Fisheries:
Taken with bottom longlines and utilized fresh for human consumption and for fishmeal.
Type material:
Holotype: Stanford University Natural History Museum collection, SU-11583, 900 mm adult male. Type Locality: Mazatlan, Sinaloa, Mexico.