Typically reaching 1.2–1.3 m (3.9–4.3 ft) in length, this shark has a unique, bright golden color on its head, sides, and fins, which was only scientifically documented in the 1980s.

Because of its abundance, the smalleye hammerhead is an economically important bycatch of artisanal gillnet fisheries throughout its range, and is used as food.

Despite being one of the most easily recognizable sharks, the smalleye hammerhead has had a long history of taxonomic confusion that still remains to be fully resolved.

Valenciennes made reference to three specimens, one from Nice in France, one from Cayenne in French Guiana, and one from the Coromandel Coast of India.

[5] For over two centuries, though, taxonomists believed Valenciennes' account matched the great hammerhead, which thus became known as Zygaena (later Sphyrna ) tudes.

[3] The smalleye hammerhead was known by a different name, Sphyrna bigelowi, coined by Stewart Springer in a 1944 issue of Journal of the Washington Academy of Sciences.

[1] Phylogenetic analyses based on nuclear and mitochondrial DNA have found that the hammerheads with the smallest cephalofoils are the most derived members of their lineage.

The mallet-shaped cephalofoil is wide and long, with a span measuring 28–32% of the body length; the leading margin forms a broad arch with indentations in the middle and on either side.

[4] The eyes, placed at the ends of the cephalofoils, are proportionately smaller than in other hammerheads and equipped with nictitating membranes (protective third eyelids).

[4] The smalleye hammerhead is found along the eastern coast of South America from Uruguay to Venezuela, though it seldom occurs further west than the Orinoco Delta southeast of Trinidad.

[4] Reports of this species from off Panama, Mexico, and western Florida are unconfirmed; records from other parts of the world are most likely erroneous, resulting from its tangled taxonomic history.

Segregation occurs by sex and age; newborns and juveniles under 40 cm (16 in) long are found in the shallowest waters, moving deeper after a few months of life.

Another shark species in the region, the yellow smooth-hound (Mustelus higmani), also feeds on shrimp and has a yellowish color, albeit not nearly as bright.

[18] A known parasite of this species is the hexabothriid monogenean Erpocotyle schmitti;[19] it may also serve as a host to common copepod ectoparasites such as Echthrogaleus coleoptratus, Pandarus satyrus, and P.

[1] Off Trinidad, reproduction occurs on a well-defined annual cycle with mating in August and September, and birthing in late May and June of the following year.

The seasonality of breeding also differs, with pregnant females found from June to October and January to April, and males in apparent reproductive condition from May to November and in March.

[16] Timid and harmless to humans,[12][13] the smalleye hammerhead is caught incidentally by inshore artisanal multispecies fisheries throughout its range, and marketed as food.

[1][4][17] The IUCN assessed this species as critically endangered in 2020, as it is subjected to intense fishing pressure, often without management, by techniques ranging from beach seine netting to trawling, and is unable to replenish this harvest.

Anecdotal evidence suggests that smalleye hammerhead catches have declined significantly off Trinidad and northern Brazil, which are likely indicative of population trends in the rest of its range.