Family Kamptosomatidae Mortensen, 1934

Diagnosis. Echinothurioida with ambulacral plates of diadematoid triads only at extreme adapical region, elsewhere forming diads, with alternate plates occluded as small secondary plates. Ambital primary spines flattened and expanded distally, others cylindrical, hollow, more or less thorny, interambulacral tubercles crenulate (emended from Fell 1966)