The Echinoid Directory

• Test inflated and thick shelled.
• Apical disc ca. 40% test diameter; dicyclic; genital plate 2 larger than the other genital plates. All plates covered in uniform coarse granulation.
• Interambulacra composed of 5-6 plates; one small rudimentary plate in each zone adapically. Interambulacral plates approximately as wide as tall, with large primary tubercle. Mamelon large and perforate; platform smooth except on adapical tubercles where it is distinctly crenulate. Areoles circular; hardly incised.
• Scrobicular tubercles coarse and strongly differentiated. Extrascrobicular granules fine and forming a narrow interradial band. Sutures not incised.
• Ambulacra narrow, sinuous, the pore zones a little depressed and wider than the perradial tuberculate zone. Pore-pairs non-conjugate, the two pores however rather broad and the interporal partition similar to the pores in width. Ambital plates and adapical plates with single primary tubercle; the perradial zone very narrow with just the occasional granule.
• Adoral ambulacral tuberculation larger with a single primary tubercle for every two pore pairs. Although sutures not clearly seen it is likely that there is an alternation between large plates bearing the tubercle and smaller demiplates separated from the perradius.
• Perignathic girdle of apophyses. No auricles.
• Spines unknown but the large size of the mamelons indicate that they were relatively massive.

Bajocian, Middle Jurassic, Madagascar.

Besairiecidaris ankarensis Lambert, 1936, p. 118, by original designation.

• Only the type species.

Cidaroida, Psychocidaridae.

Monotypic; subjective junior synonym of Caenocidaris.

Although Mortensen (1951) treated this genus as a possible hemicidaroid, the type specimen clearly has a perignathic girdle of auricles and Lambert was correct in placing this taxon in the Cidaroida.

The mamelons that increase rapidly in size towards the apex and which have only small rudimentary perforations, together with the pseudocompounding of the ambulacra adorally are all features seen in Caenocidaris and Paracidaris. There is little to differentiate it from Caenocidaris. The absence of mamelonate tubercles outside the scrobicular rings does however seem to be a distinctive trait.

Lambert, J. 1936. Les echinides du Bajocien du Plateau de l'Ankara. in Besairie, 1936 Recherches geologiques a Madagascar 1ere suite. La geologie du Nord-Ouest. Memoires de l'Academie malgache 21, 116-120.