The Echinoid Directory

• Test large and depressed; plating rather fragile.
• Test plating more or less flexible adapically; plating imbricate.
• Apical disc usually monocyclic; periproct large with distinct periproctal plates only around the rim. Genital plates strongly projecting interradially.
• Ambulacra narrow and straight; pore-pairs non-conjugate, in very weakly offset triads. Becoming more perradial in position towards the peristome.
• Ambulacral plating trigeminate at ambitus with single large primary tubercle per plate. Adoral ambulacra trigeminate with primary tubercles present close to the peristome.
• Interambulacral zone wide, with ambital plates distinctly wider than tall.
• Primary tubercles forming row on ambital plates on oral surface; all tubercles perforate and crenulate; tuberculation highly reduced aborally, plates almost naked.
• Bifurcating naked zone adapically in interambulacra.
• Peristome relatively small; buccal notches small and rounded.
• Spines long and slender; hollow, with verticillate ornament.

Recent, Malay archipelago.

Astropyga denudatum de Meijere, 1902, by original designation.

• E. denudataum (de Meijere, 1902); Recent, Malay archipelago.
• E. debilis Mortensen, 1940; Recent, Mindanao.

Diadematoida; Diadematidae.

Possibly paraphyletic by exclusion of Goniodiadema.

Like Chaetodiadema but with ambulacral plating remaining compound to the peristome. Differs from Astropyga in having uniserial, well-spaced pore-pairs that move into a more perradial position adorally. Its spines also lack any meshwork within the lumen.
Agassiz, A & Clark, H. L. 1908. Hawaiian and other Pacific echini. Memoirs of the Museum of Comparative Zoology, 34: 49-132.

Mortensen, T. 1940. A monograph of the Echinoidea. Volume III. 1, Aulodonta. C. A. Reitzel, Copenhagen.