The Echinoid Directory

• Test ovate with almost no anterior sulcus; rather depressed in profile.
• Apical disc ethmolytic, with 3 (rarely 2) gonopores (no gonopore in plate G2); subcentral.
• Anterior ambulacrum narrow and weakly sunken adapically but flush by the ambitus; pore-pairs and tube-feet enlarged adapically; uniserially arranged.
• Other ambulacra petaloid and sunken, anterior petals longer than posterior petals; petals cruciform and not flexed. Perradial zone wider than pore-pairs. Petals weakly sunken in males (figured above), deeply sunken and enlarged in females.
• Periproct longitudinal, on vertically truncate face.
• Peristome large and kidney-shaped; facing forwards; labral plate projecting.
• Labral plate long and stout, extending to third ambulacral plate; in broad contact with sternal plates.
• Aboral tuberculation fine, uniform and dense. Oral tubercles also dense and uniform.
• Well-developed peripetalous fasciole passing around the base of petals. Lateroanal band present but only in juveniles. In interambulacrum 1b fascioles merge on plate 5.
• No subanal penicillate tube feet developed.
• Sexual dimorphism in gonopore size and petal development (females brood juveniles in petals). Petals deepen only in their outer part.

Recent, circum-Antarctic.

Pseudabatus nimrodi Koehler, 1911, p. 60, by original designation.

• P. nimrodi Koehler, 1911; Recent, circum-Antarctic.
• P. beatriceae Larrain, 1985; Recent, Antarctic.
• P. shackletoni (Koehler, 1911); Recent, Antarctic.
• P. ingens (Koehler, 1926); Recent, Antarctic.

Spatangoida, Paleopneustina, Paleopneustidae.

?Subjective junior synonym of Amphipneustes Koehler, 1900

The type species is derived in having the petals sunken only at some distance from the apex in the females. The taxon differs from Abatus in having a long labrum which extends to at least the third ambulacral plate and is almost as long as the sternal plates. Pseudabatus, Parapneustes and Amphipneustes, form a closely related clade characterised by having three gonopores, a large and subquadrate labral plate and poorly developed fascioles.

Koehler, R. 1911. Astéries, ophiures, et échinides. British Antarctic Expedition 1907-1909 2, p. 60.

Mortensen, T. 1951. A monograph of the Echinoidea V Spatangoida 2. C. A. Reitzel, Copenhagen