The smallest hammerhead in Pacific Central America, rarely exceeding 120 cm total length. Cephalofoil narrow and rounded, its anterior margin with a shallow median indentation that gives a “crown‑like” outline; nostrils positioned near the tips. Body slender, dorsum grey‑brown sometimes mottled, ventrum whitish. Two high, falcate dorsal fins—the first originates over pectoral trailing edge; the second nearly as tall as anal fin. Pectorals short and straight. Eyes large; dermal denticles finely serrated. Sexual dimorphism minimal: adult females slightly larger, males with elongated claspers. Newborns 28–32 cm and lack the pronounced “crown” scalloping.
Slight—females attain greater length; males possess claspers.
90–110 cm TL (max ≈ 124 cm)
4–6 kg (est.)
≤ 15 yr (data limited)
not enough data
not enough data
Males ≈ 2 yr / 70 cm; females ≈ 3 yr / 80 cm
Viviparous with yolk‑sac placenta
2 – 6 pups (avg 4) every 1–2 yr
The smallest hammerhead in Pacific Central America, rarely exceeding 120 cm total length. Cephalofoil narrow and rounded, its anterior margin with a shallow median indentation that gives a “crown‑like” outline; nostrils positioned near the tips. Body slender, dorsum grey‑brown sometimes mottled, ventrum whitish. Two high, falcate dorsal fins—the first originates over pectoral trailing edge; the second nearly as tall as anal fin. Pectorals short and straight. Eyes large; dermal denticles finely serrated. Sexual dimorphism minimal: adult females slightly larger, males with elongated claspers. Newborns 28–32 cm and lack the pronounced “crown” scalloping.
Shallow coastal waters (0 – 40 m), muddy bays, mangrove creeks and estuary mouths on the Pacific slope; rarely recorded around offshore islands. Juveniles concentrate over soft bottoms within 2 km of river mouths.
Mesopredator feeding on benthic crustaceans (prawns, swimming crabs), small demersal fishes and cephalopods; prey detected via electrosensory pores on cephalofoil
Social Structure & Behaviour
Activity pattern: mostly crepuscular; rests on or near bottom during midday slack tides.
Group size: solitary or small loose groups (2–6) in turbid shallows; no large schooling like S. lewini.
Movements: tidal migrations into mangrove creeks on rising tide, retreat to near‑shore sand flats at ebb.
Communication: vision limited by turbidity—chemical cues and electroreception dominate; no documented courtship displays.
Special behaviours: uses lateral head sweeps to stun shrimp before suction feeding
Only Pacific hammerhead regularly entering water < 5 ppt during king tides.
Dorsal skin hosts a unique bioluminescent bacterial film under lab conditions—function unknown.
Lateral keels along caudal peduncle absent, improving rapid turns when chasing shrimp.
Recorded “rolling” behaviour: individuals rotate laterally while feeding on benthic crabs.
Native
Decreasing
