The Echinoid Directory

• Test large, depressed; plating imbricate, strongly so adapically.
• Apical disc relatively small and not bound to the corona; monocyclic, with genital plates projecting strongly. Periproctal zone large.
• Ambulacra narrow and almost straight; composed of simple plates throughout.
• Pore-pairs non-conjugate, the pores laterally elongate. Perradial tuberculate zone narrow (approximately equal to pore-pair width); each plate with marginal primary tubercle and smaller inner granules.
• Interambulacral zones wide with about 12 laterally elongate plates in a column.
• Single large primary interambulacral tubercle on each plate surrounded by small heterogeneous granules.
• Primary interambulacral tubercles crenulate and perforate; mamelon relatively small; areoles confluent adorally separated above the ambitus and absent from adapical plates.
• No scrobicular tubercles and spines differentiated around areole.
• No buccal notches.
• Lantern supports (apophyses) developed on first interambulacral plates.
• Primary spines cylindrical with smooth, unornamented shaft and no cortex.

Early Triassic (Scythian); USA.

Lenticidaris utahensis Kier, 1968, p. 1000, by original designation. Holotype: National Museum of Natural History, Smithsonian Institution S5087.

• Only the type species.

Cidaroida (stem group).

Monotypic.

Similar to interambulacral plate fragments referred to as Mesodiadema by Kier (1968) and others in having wide adradial and interradial zones of secondary tuberculation, but differs from that taxon in having strongly crenulate tubercles. The type species of Mesodiadema is a primitive Irregularia from the Lower Jurassic and its relationship to the Triassic material unknown. Lenticidaris differs from Miocidaris in having wider interambulacral plates which are much more imbricate and spines that are smooth.

Isolated interambulacral plates from the Carnian of Italy have been attributed to this genus by Vadet (2000). However, such plates are strictly indeterminate and could belong to one of a number of different genera.

Kier, P.M. 1968. The Triassic echinoids of North America. Journal of Paleontology 42, 1000-1006.

Vadet, A. 2001. Revision des echinides de Saint Cassian et evolution des echinides post-carboniferes. Memoires de la Societe Academique du Boulonnais 20, 1-116.