The Echinoid Directory

Stem group Clypeasteroida with:

• apical system monobasal with four gonopores;
• ambulacra petaloid adapically, open distally; ambulacra narrower than interambulacra;
• phyllodes narrow; no expansion of pore zones towards peristome; primary elements alternating with demiplates in oral area. No accessory pores;
• pores single beneath petals;
• periproct longitudinal; submarginal to oral;
• well developed lantern in adults;
• perignathic girdle composed of paired, slender auricles that are of mixed ambulacral and interambulacral in origin.

Late Palaeocene to Eocene of North Africa, Arabian Peninsula, India, Madagascar and Europe

Distinguished from Oligopygidae only by the lack of superficial demiplates. Distinguished from Plesiolampadidae by the large perignathic girdle that is present in adults.  Distinguished from Echinolampadidae by longitudinal periproct.