The Echinoid Directory

Contributed by Heinke Schultz, August 2007

Lissodiadema Mortensen, 1903 p. 393

[(= Leptodiadema Agassiz & Clark, 1907, type species L. purpureum Agassiz & Clark, 1907) ]

Diagnostic Features
  • Test flattened, plating rather thin, with slightly imbricating sutures, weakly flexible adapically along interradial suture.
  • Apical disc with ocular plates broadly insert, except Ocular II, which may be exsert or narrowly insert; periproct relatively small, distinct anal cone.
  • Ambulacra straight, about 1/3 the interambulacral width; pore-pairs uniserial, slightly crowded at the peristomial edge. Pore-pairs positioned at the adradial suture aborally and at the ambitus, moving towards the centre of the plate on the oral side, leaving space for an adradial series of irregularly sized tubercles. Pore zones broad, widened on the aboral side,  Dense irregular tuberculation with primaries hardly differentiated, sometimes tending to form vertical rows; on oral side two irregular series of primaries.
  • Interambulacra with three subequal tubercles on ambital plates, alternating with smaller ones, which often lie one above the other; adapically naked median area.
  • Primary tubercles perforate and non-crenulate or very slightly crenulate.
  • Peristome large and raised with small buccal plates; notches broad and shallow.
  • Spines long, thin, brittle and hollow; shaft not verticillate, but smooth.
Distribution Recent, Pacific
Name gender neuter
Type Lissodiadema lorioli Mortensen, 1903, by original designation
Species Included
  • L. lorioli Mortensen, 1903; Recent, Indonesia.
  • L. purpureum Agassiz & Clark, 1907; Recent, Hawaii and Guam.
Classification and/or Status Diadematoida, Diadematidae

Remarks The type species was established on the basis of a single 22 mm diameter individual. It has aboral naked interambulacra and well developed adradial tubercles on oral side in its ambulacra like Chaetodiadema and Goniodiadema. It differs from the other diadematids by almost or entirely smooth tubercles and by non-verticillate spines.

Mortensen, T. 1903. The Danish Ingolf-Expedition 1895-1896. Vol. 4, No. 2. Echinoidea, pt. 1.Copenhagen, 198 pp.

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