The Echinoid Directory

• Test subconical with raised apical disc; plating relatively thick.
• Apical disc more than 80% test diameter; subconical. Dicyclic; genital plates identical in size; uniformly covered in dense granules. Ocular plates greatly reduced and periproctal zone relatively small.
• Sexually dimorphic; females with large brood chambers developed in the five genital plates.
• Interambulacra with 5 plates in a series. Primary tubercles perforate and non-crenulate; areoles circular and incised. Areoles separated on all plates. Mamelons becoming larger adapically.
• Scrobicular tubercles differentiated; extrascrobicular zones narrow with just a single band of secondary tubercles and granules on ambital plates.
• Ambulacra narrow and sinuous. Pore zones incised; pore-pairs narrow, oblique, non-conjugate and with narrow interporal ridge.
• Perradial zone with marginal series of primary tubercles and inner series of smaller secondary tubercles.
• Peristome smaller than apical disc; plating unknown.
• Primary spines unknown; secondary spines flattened.

Upper Cretaceous (Maastrichtian); Antarctic and Spain.

Almucidaris durhami Blake & Zinsmeister, 1991, p. 632, by original designation.

• Only the type species.

Cidaroida; Cidaridae; Cidarinae.

Monotypic.

This beautiful little sea urchin is unmistakable because of the highly distinctive brood pouches developed in genital plates of females.

Blake, D. B. & Zinsmeister, W. J. 1991. A new marsupiate cidaroid echinoid from the Maastrichtian of Antarctica. Palaeontology 34, 629-635.