The Echinoid Directory

Niponaster Lambert, 1920, p. 168(26)

[=Mokotibaster Lambert, 1933, p. 17, type species Mokotibaster hourcqui, Lambert 1933]

Diagnostic Features	Test ovate with no anterior sulcus. Test subconical in profile, rounded oval in outline without truncate posterior face; base flat. Apical disc ethmophract with four gonopores; central. Ambulacra all similar; the five ambulacra petaloid aborally and more or less flush. Ambulacrum III slightly narrower than other ambulacra. Petals long and parallel; open distally. Pore-pairs circumflexed. Peristome small, circular and downward facing. Shallow groove between peristome and anterior border. Plastron amphisternous. Labrum longitudinally elongate; subtrigonal; extending to ambulacral plate 4. Sternal plates symmetrical and forming only a small part of the oral surface; rear of sternum at ambulacral plate 7. Three pairs of post-sternal plates also incorporated into the plastron, biserially arranged. Periproct inframarginal; circular. No fascioles. Aboral tubercles small and set in a groundmass of fine granules.
Distribution	Upper Cretaceous: 'Senonian', Japan; Maastrichtian, Madagascar.
Name gender	masculine
Type	Niponaster hokkaidensis, Lambert 1924, p. 17, by original designation.
Species Included	N. hokkaidensis (Lambert, 1924); Upper Cretaceous, Japan. N. nakaminatoensis Saito, 1959; Upper Cretaceous, Japan. N. hourcqui Lambert, 1933; Maastrichtian, Madagascar.
Classification and/or Status	Spatangoida, stem group (toxasterids). Presumed monophyletic.
Remarks	Differs from Toxaster in having all five ambulacra petaloid aborally, and with no truncate posterior face, the periproct being inframarginal, near the base of the test. It also has a more triangular-shaped labral plate, and no enlarged subanal pore-pairs. Macraster has all five ambulacra petaloid, but has its periproct on the posterior truncate face. Niponaster also differs from Macraster in having almost no frontal groove and it differs from Aphelaster in having an inframarginal periproct. Morishita, A. 1955. Cretaceous echinoid, Niponaster from the Island of Awazi, Japan. Transactions and Proceedings of the Palaeontological Society of Japan 20, 99-100, pl. 15. Nisiyama, S. 1968. The echinoid fauna from Japan and adjacent regions part II. Palaeontological Society of Japan Special Papers 13, 1-491, pls 1-30.