Döderlein, 1916: 424; 1936: 331; Clark and Rowe 1971: 55; A.M.

Clark 1993: 310 (checklist)

Diagnosis. Body stellate (R/r=2.0–3.0, seldom>3.0) with strongly arched disk, elongate, triangular arms. Distal abactinal, actinal and especially marginal plates covered with distinct, even-sized, projecting granules. Abactinal–lateral regions with distinctly reticulate plates showing well-defined pore areas. Primary plates with spines or conical tubercles arranged in longitudinal series in most species. Distal inferomarginal plates with an enlarged spine or conical projection in most species. Intermarginal pore areas weakly developed or absent. Modified from Marsh and Fromont (2020).

Comments. Pentaceraster includes 15 species that occur widely throughout the Indo-Pacific. The diagnosis follows Marsh and Fromont (2020), but boundaries for the concept of Pentaceraster have not been tested or reviewed since their establishment (Döderlein, 1916, 1936). Other oreasterid genera, such as Poraster, and the typological Oreaster, differ from Pentaceraster by relatively few characters and invite additional scrutiny, especially as further data on variation among species within these genera has produced taxonomic overlap. For example, Doderlein’s key (1936) differentiates the Atlantic Oreaster from Pentaceraster by the presence of low dorsal spines, a character observed in highly variable Indo-Pacific species, such as Pentaceraster alveolatus or Pentaceraster mammilatus. Character variation among Pentaceraster species is similarly problematic, with several species displaying character variation that is at odds with established species concepts, particularly as outlined by Döderlein (1916, 1936).