Arachnanthus nocturnus den Hartog, 1977 is now accepted as Isarachnanthus nocturnus (Hartog, 1977) Distribution In both Caribbean and East Atlantic subtropical areas. Habitat Anemone living inside tubes buried in mud, sand or fine gravel in areas of sand and coral rubble, down to 25 m. Retracts immediately by disturbance.

This species was described by den Hartog (1977) based on specimens from Curaçao. The specific epithet is related to the nocturnal behavior of this species. This is the most studied species of the genus, as the larval development has been described and the taxonomy has been reviewed with molecular data (Stampar et al. 2012, 2015c).