Ophiuraster patersoni Litvinova, 1998 is shown to be identical with the small postlarva of Ophiomyxa serpentaria Lyman, 1883, which is described here for the first time. The smallest individuals have an asteroid-like habitus with a disk diameter of 1.8 mm and short, not sharply set off arms. The whole animal is covered with thick, in small postlarvae transparent, skin, which thickens further with growth. The postlarvae are characterised by large primary plates, large, swollen lateral arm plates, the first of which surround the disk margin, and bare patches of skin on the interradial disk. The terminal arm plate is bulbous and hollow, in individuals of 2.5 mm it has a wide distal opening. The mouth papillae are flat and rugose as is typical for Ophiomyxa Müller & Troschel, 1840. Dorsal arm plates are absent in all stages, while ventral arm plates are present from about 2.0 mm disk diameter, as well as a small hook-shaped arm spine. Further disk growth is slower than the increase in arm length. Thus, individuals with 2.5 mm disk diameter have between 11 and 16 arm segments, two arm spines and two lateral mouth papillae. The large first lateral arm plates move ventrally during growth and probably later form the adoral shields. The taxonomic status of the remaining three species of Ophiuraster H. L. Clark, 1939 is discussed.
Echinodermata, Ophiuroidea, Ophiuraster patersoni, Ophiomyxa serpentaria, postlarvae, development, growth, Atlantic Ocean.