The Echinoid Directory

 Spatangoids with:

• thick-shelled test with flat base and domed upper surface
• ethmolytic apical disc
• ambulacrum III pores rudimentary on aboral surface
• paired ambulacra flush and petaloid; petals long, parallel-sided, open distally and without occluded plates at end
• peristome subcentral
• ambulacra forming distinct channels orally leading to the peristome; phyllode pore-pairs well developed almost to ambitus; very numerous
• labral plate short and wide; sternal plates long and symmetrical; episternal plates broadening posteriorly and biserially offset; not indented by ambulacral plates
• periproct large and supramarginal to inframarginal.

Eocene; Caribbean and Spain.

Kier (1984) argued that Asterostoma was so different that it deserved its own family. Its most characteristic features are the subcentral mouth and long extensive phyllodes extending almost to the ambitus. 

Possibly originating from Heterolampas.

Kier, P. M. 1984. The fossil spatangoid echinoids of Cuba. Smithsonian Contributions to Paleobiology 55, 1-334.