The Echinoid Directory

• Test elongate and subquadrate with convex anterior and steeply oblique and truncated posterior.
• Apical disc disjunct; compact; anterior part tetrabasal with 4 gonopores and 3 ocular plates. Ocular plates II and IV small and separated by genital plate 2. Posterior oculars immediately above periproct and forming upper border to the opening.
• Genital plate 5 preserved as a slender imperforate crescentic element around the lower half of the periproct.
• Paired ambulacra flush; apetaloid; pore-pairs small, double and oblique.
• Ambulacrum III sometimes weakly sunken adapically and with differentiated pore-pairs with strong interporal partition.
• Weak sulcus on oral surface leading to downward facing peristome. Peristome circular to slightly longer than wide.
• Phyllodes short, composed of 4-6 enlarged pore-pairs only. One peribuccal plate in each ambulacral zone with two pore-pairs.
• Posterior interambulacral plating with first three plates uniserial or almost so (some specimens with biserial plating) plastron narrow; adjacent periplastronal zones also narrow.
• Periproct supramarginal; towards top of steeply sloping posterior face.
• Enlarged subanal pore-pairs present.
• Aboral tuberculation comprises fine tubercles set in groundmass of granules.

Middle Jurassic (Callovian) to Lower Cretaceous (Hauterivian), Europe.

Nucleolites granulosus Goldfuss, 1827, p. 28, by subsequent designation of Desor, 1857, p. 201.

• D. granulosus (Goldfuss, 1827); Oxfordian-Kimmeridgian, Europe.
• D. moeschi Desor, 1858; Callovian-Oxfordian, Europe, Russia.
• D. dalloni Lambert; Berriasian, Spain.
• D. subelongatus (d\'Orbigny, 1853); Neocomian (Berriasian-Hauterivian), France, former Soviet Union.
• D. anasteroides (Lambert, 1893);

Irregularia, Stem group Atelostomata, Disasteridae.

Monophyletic.

Distinguished from all other disasteroids by having a compact anterior part of the apical disc with ocular plates II and IV small but distinct and set in the angle between adjacent genital plates.

Agassiz, L. 1836. Prodrome d'une monographie des Radiaires ou Échinodermes. Mémoires de la Société des Sciences naturelles de Neuchâtel, 1, 168-199.

Barras, C. 2006. British Jurassic irregular echinoids. Monograph of the Palaeontographical Society, 1-168, pls 1-14 (publication number 625).

Jesionek-Szymanska, W. 1963. Echinides irreguliers du Dogger de Pologne. Actes Palaeontologica Polonica 8(3), 293-396, pls 1-7.

Smith, A.B. 1995. Echinoids from the Jurassic Oxford Clay of England. Palaeontology 38, 743-755.

Solovjev, A. 1971. Late Jurassic and Early Cretaceous disasterids of the USSR. Transactions of the Palaeontological Institute, Academy of Sciences of the USSR 131, 1-120, pls 1-16 [in Russian].