The Echinoid Directory

• Test small; subglobular; plating fragile but firmly tesselated.
• Apical disc monocyclic with periproct rim circular. Plates membrane embedded and not abutting coronal plates.
• Ambulacral straight and relatively narrow; pore-pairs non-conjugate; uniserial throughout.
• Ambulacral plating pseudocompound with with single large primary tubercle on every third plate which is much enlarged compared to the others; primary tubercles forming an alternate series down the perradius.
• All three plates extend across the full ambulacral width.
• Interambulacral zone composed of pentagonal plates with a single large primary tubercle.
• Primary tubercles perforate and crenulate; secondary tuberculation confined to plate margins.
• Peristome with shallow, rounded buccal notches.
• Spines slender, and verticillate. Lumen filled with open mesh of horizontal partitions and vertical pillars.

Recent, Indo-Pacific and Caribbean.

Aspidodiadema tonsum A. Agassiz, 1878, by original designation.

• A. tonsum A. Agassiz, 1878; Recent, Indonesia.
• A. jacobi A. Agassiz, 1880; Recent, Caribbean.
• A. meijerei Doderlein, 1906; Recent, Malaysia.
• A. hawaiiense Mortensen, 1939; Recent, Hawaii.
• A. nicobaricum Doderlein, 1901; Recent, Malaya.
• A. arcitum Mortensen, 1939; Recent, Hawaii.
• A. africanum Mortensen, 1939; Recent, South Africa.

Acroechinoidea; Aspidodiadematoida; Aspidodiadematidae.

Presumed monophyletic.

Differs from Plesiodiadema and Gymnotiara in having every third ambulacral plate greatly enlarged at the ambitus and bearing a large primary tubercle; these tubercles forming a single perradial series offset to left and right.

Agassiz, A. 1879 Preliminary report on the echini of the exploring expedition of H. M. S. “Challenger”, Sir C. Wyville Thomson chief of civilian staff. Proceedings of the American Academy of Arts and Sciences, 14, 190-212.

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