The Echinoid Directory

• Apical disc hemicyclic, rarely dicyclic.
• Periproctal opening very large (> 75% apical disc diameter).
• Ambulacral plating trigeminate, with pore-pairs dense and forming a single adradial band.
• Primary ambulacral tubercle developed on every second or third plate.
• Interambulacral plates with central primary tubercle and numerous slightly smaller secondary tubercles; plate otherwise covered in rather dense granules.
• Spines short and rather delicate; adoral ones curved.
• Globiferous pedicellariae with tubular blade bearing 2-5 pairs of lateral teeth.

Recent; Antarctica.

Sterechinus antarcticus Koehler, 1901, by original designation.

• Sterechinus antarcticus Koehler, 1901; Recent, Antarctic, 100-1080 m.
• S. agassizi Mortensen 1910; Recent, E. coast of S. America, Falkland Islands. 75-970 m.
• S. diadema (Studer, 1876); Recent, Keurgelen Islands, 5-220 m.
• S. neumayeri (Meissner, 1900); Recent, Antarctic & S. America.
• S. dentifer Koehler, 1926; Recent, Antarctic.

 Camarodonta; Echinoida; Echinidae.

Monophyletic.

Differs from Echinus in having a hemicyclic apical disc with a proportionally much larger periproct, and in having plates much more densely covered in granulation. In life this provides the animal with a dense, hair-like felt in amongst the rather fine primary spines. Confined today to the circum-Antarctic region. Very similar to Selenechinus which differs primarily in that its globiferous pedicellariae have a single lateral tooth. In terms of test characters the two are almost identical save that Sterechinus has a much larger periproct in comparison to the size of its apical disc than Selenechinus.

Hypechinus Desor, 1856 may be a senior synonym of this genus but is based on a fossil that remains very incompletely known.

Koehler, A. 1900 (December). Bulletin de l'Academie Belgique (3) 38, p. 815.