This species is endemic to the Eastern Pacific, and is only found in the Galápagos Islands. However, there have been no recent sightings of this species. It has evidently disappeared from the Galápagos during the intense El Niño event of 1982-1983 (Grove 1985), when greatly increased sea temperatures had strong adverse effects on the islands marine fauna and flora. Its sister species, A. hirundo occurs in a similar environment, the Revillagigedos Islands, near the northern limit of the Eastern Tropical Pacific. It may be possible that populations of A. eupalama may still exist on islands off Peru that have warm temperate conditions, such as the Lobos Islands.