The Echinoid Directory

Kamptosoma Mortensen, 1903, p. 60

[= Cuenotia Lambert & Thiery, 1914, p. 273 (illegal replacement name) ]

Diagnostic Features
  • Test plating fragile and flexible.
  • Apical disc monocyclic with elongate, narrow oculars and composite genital plates.
  • Ambulacra rather wide; almost as wide as interambulacral zones at ambitus.
  • Ambulacral plating trigeminate at apex but mostly bigeminate, with alternate primary and occluded plates, the occluded plates being centrally positioned.
  • Interambulacral zone wide, with ambital plates distinctly concavo-convex and wider than tall.
  • Primary tubercle on ambital and subambital interambulacral plates; these tubercles perforate and crenulate. Elsewhere tuberculation reduced and plates almost naked.
  • Peristome relatively small with 10 enlarged buccal plates with tube feet plus a few small peristomial plates bearing tube feet around the edge.
  • Spines very long and slender; hollow and thorny without hyaline hoof.
  • Sphaeridia on occluded plates.
Recent, Pacific (abyssal).
Name gender neuter
Phormosoma asterias A. Agassiz, 1881 by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Euechinoidea; Echinothurioida; Kamptosomatidae.



Easily differentiated from all other echinothurioids by its crenulate tuberculation, the alternating primary and demi-plates throughout most of the ambulacra, and the presence of 10 large buccal plates on the peristome. The presence of buccal plates and the crenulate tubercles are characters Kamptosoma shares with diadematoids.

Although Fell (1966) placed Kamptosoma in the Diadematoida, Mortensen (1935) and Mironov (1972) both preferred to retain it in the Echinothurioida.

Mironov, A. N. 1972. On relationship of the group of flexible urchins and systematic status of the genus Kamptosoma Mortensen (Echinoidea, Echinothuriina). Zoologiske Zhurnal 51, 381-387 [in Russian].

Mortensen, T. 1903. The Danish Ingolf-Expedition 1895-1896. Vol. 4, No. 2. Echinoidea, pt. 1, 198 pp., 21 pls. Bianco Luno, Copenhagen.

Mortensen, T. 1935. A Monograph of the Echinoidea. II. Bothriocidaroida, Melonechinoida, Lepidocentroida, and Stirodonta. C. A. Reitzel, Copenhagen, 647 pp.

Mooi, R., Constable, H., Lockhart, S. & Pearse, J. 2004. Echinothurioid phylogeny and the phylogenetic significance of Kamptosoma (Echinoidea: Echinodermata). Deep Sea Research II 51, 1903-1919.