The Echinoid Directory

 Stem group echinoids with:

• test flattened in profile; composed ambulacral and interambulacral plates; plating strongly imbricate
• ambulacral zones biserial or multiserial; expanded on oral surface
• pore-pairs on oral and aboral surfaces differentiated - small and simple pore-pairs adapically, large pore-pairs with circular peripodial rims adorally
• no internal perradial flanges on ambulacral plate
• interambulacra composed of multiple columns of thin rhomboidal plates
• small mamelonate tubercles on interambulacral plates but without well defined areole.

Lower Carboniferous (Visean) to Upper Permian, USA, Europe.

The presence of specialised adoral pore-pairs (and presumably tube-feet) characterizes this clade. Interambulacral plating is more imbricate than in Palaechinidae, and there are primary tubercles, which are never seen in Palaechinidae. Lepidesthidae have expanded ambulacra with many columns, but the pore-pairs remain simple throughout.

Smith, A. B. 1984. Echinoid Palaeobiology. George Allen & Unwin, London.