The Echinoid Directory

• Test rounded in profile with height about half of diameter; up to 38 mm in diameter. Plating rather thin.
• Apical disc large, plates lost in all specimens and so arrangement unknown.
• Ambulacra with all elements reaching the midline. Pore-pairs in arcs of three from the ambitus adorally and crowded to form phyllodes adorally.
• Primary tubercle overlapping three elements to form compound plates at ambitus and below; plating 2+1 adapically. Primary tubercles always much smaller than interambulacral tubercles.
• Interambulacral plates carrying a single large primary tubercle; plates wider than tall at ambitus, but becoming more equant adapically. Areoles confluent. Secondary granules confined to the adradial and interradial margins of the plate.
• Tubercles with large boss, small perforate mamelon and distinct crenulation.
• Peristome large with large U-shaped buccal notches.
• Spines unknown.
• Teeth without keel.

Middle Jurassic (Bajocian) of France and England.

Culozoma baroini Vadet & Slowik, 2001, p. 35, by original designation.

• Only the type species.

Acroechinoidea, Aspidodiadematoida, Aspidodiadematidae.

Monotypic.

In describing this taxon Vadet & Slowik (2001) compared it with the Jurassic aspidodiadematid Gymnotiara. Culozoma differs significantly from that taxon, in having trigeminate ambulacral plating and pore-pairs in triad arcs and becoming crowded adorally. A British specimen, BMNH E76953, from the Bajocian of Haresfield, Gloucester (illustrated above), shows the lantern and confirms that the teeth are without a keel.

In the absence of lantern characters, it is differentiated from contemporary Trochotiara in having wide, deep and rounded buccal notches and much smaller primary ambulacral tubercles, that never approach the size of interambulacral tubercles. It differs from Acrosalenia in having large primary interambulacral tubercles adapically and a thinner, more fragile test.

Very close to the type species of Gymnotiara, G. varusense in test morphology and ambulacral structure differing only in having fully formed primary tubercles on its adapical interambulacral plates.

Vadet, A. & Slowik, D. 2001. Les oursins du Bajocien de Liocourt. Memoires de la Societe Academique du Boulonnais. Serie Histoire Naturelle 22, 1-48.