Acheronaster sp.

Comments. The Rapa Nui species displays several characters which identify it as Acheronaster, including the high disk, the triangular, sharply sloping arms, the distinct, rolled marginal plate periphery and the complete absence of spination on any of the marginal plate surfaces.

Mecho et al. (2019: Fig. 11) reported an oreasterid showing a white body with brick red spines and highlights. This species differs in the absence of distinct, pointed abactinal spination on much of the surface and having larger, flattened primary and abactinal disk plates. Color is also substantially different. Acheronaster tumidus is described as primarily orange with bars and other patterns (H.E.S. Clark 1982: 41). Comparison of this species with that of Acheronaster tumidus, shows it to be a second, likely undescribed, species of Acheronaster.