The Echinoid Directory

• Test small (no larger than 9 mm), subglobular; plating non-imbricate.
• Apical disc large and not bound to the corona; plating unknown. Outline of disc pentaradial with points at ambulacra.
• Ambulacra narrow and almost straight; composed of simple plates throughout.
• Pore-pairs rather large and non-conjugate. Perradial tuberculate zone very narrow (equal to pore-pair in width); with single tubercle on each plate; tubercles relatively small and non-contiguous.
• Interambulacral zones with about 7 pentagonal plates in a column.
• Single large primary tubercle on each interambulacral plate with very prominent imperforate, non-crenulate mamelon. Areoles circular and confluent at ambitus. Mamelons largest at ambitus.
• Single arc of scrobicular tubercles on adradial and interradial margins; no interradial zone of granules.
• Interambulacral plates with concave centre internally.
• Peristome similar in size to apical disc; no buccal notches.
• No perignathic girdle developed on interior of test.

Late Triassic (Carnian); Italy.

Megaporocidaris mariana Kier, 1977, p. 23, by original designation.

• Only the type species.

?Euechinoidea stem group, Triadocidaridae.

Monotypic.

Differs from Levicidaris in having much higher ambulacral plates with smaller tubercles and more circular pore-pairs. The mamelons in Levicidaris increase in size adapically, but are largest at the ambitus and decrease adapically in Megaporocidaris.

Kier, P.M. 1977. Triassic echinoids. Smithsonian Contributions to Paleobiology 30, 1-88.

Kier, P. M. 1984. Echinoids from the Triassic (St Cassian) of Italy, their lantern supports, and a revised phylogeny of Triassic echinoids. Smithsonian Contributions to Paleobiology 56, 1-41.