The Echinoid Directory

• Test ovate with only the faintest of anterior sulcus. Test subconical in profile without truncate posterior face.
• Apical disc ethmophract with four gonopores (genital plate 2 separating the posterior two genital plates but not the posterior ocular plates); central.
• Ambulacra all similar; the five ambulacra petaloid aborally and extremely weakly sunken.
• Petals long and parallel with smooth, undivided perradial zone.
• Peristome small, circular and downward facing. Shallow groove between peristome and anterior border.
• 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.

Upper Cretaceous (Maastrichtian), Madagascar.

Mokotibaster hourcqui, Lambert, 1933, p. 17, by original designation.

• Only the type species.

Spatangoida, stem group (toxasterids).

Monotypic; subjective junior synonym of Niponaster Lambert, 1920.

Smith & Jeffery (2001) associated this taxon with Micraster and included several other species within this genus. However, none of these have the inframarginal periproct or distinctive plastron structure that sets the type species as so distinct from the micrasterids. Mokotibaster is clearly a derived toxasterid rather than a micrasterid, since the rear of the episternal plates does not coincide with ambulacral plate 6. It appears indistinguishable from the less well studied Niponaster.

Lambert, J. 1936. Nouveaux echinides fossiles de Madagascar. Madagascar Annales geologiques du Service des Mines 6, 9-32.

Smith, A.B. & Jeffery, C.H. 2000. Maastrichtian and Palaeocene echinoids: a key to world faunas. Special Papers in Palaeontology 64, 1-406.