The Echinoid Directory

• Apical disc monocyclic, with ocular and genital plates forming an unbroken circle.
• Ambulacra trigeminate, with a single large element reaching the perradial suture and two small demiplates positioned centrally and abutting one another. Only becoming adradial in position close to the apex and peristome.
• Pore-pairs arranged in three series on the oral surface.
• Primary ambulacral tubercle on every second or third principle plate.
• Ambulacra about half the width of interambulacra at the ambitus.
• Interambulacral plates with prominent membranous gaps on oral surface only.
• A single primary interambulacral tubercle on every other plate only; rest of plate with just sparse granulation.
• Shallow buccal notches.
• Only ambulacral plates extending over the peristome, with pore-pairs arranged uniserially.
• Spines with expanded cone-shaped hyaline hoof.

Miocene, Portugal; Recent, Atlantic and Pacific.

Calveria hystrix Thomson, 1872, by original designation.

• C. hystrix (Thomson, 1872); Recent, Atlantic.
• C. gracile (Agassiz, 1881); Recent, Japan to Philippines.

Euechinoidea; Echinothurioida; Echinothuriidae; Echinothuriinae.

Potentially paraphyletic.

Differs from Araeosoma in having obvious membranous gaps between interambulacral and ambulacral plates only on the oral surface. It also lacks the distinctive dactylous pedicellariae of that genus.

The cladistic analysis of Mooi et al (2004) places Calveriosoma as the most primitive extant Echinothuriinae.

Mooi, R., Constable, H., Lockhart, S. & Pearse, J. 2004. Echinothurioid phylogeny and the phylogenetic significance of Kamptosoma (Echinoidea: Echinodermata). Deep Sea Research II 51, 1903-1919.

Mortensen, T. 1935. A monograph of the Echinoidea. Volume 2, Bothriocidaroida, Melonechinoida, Lepidocentroida and Stirodonta. C.A. Reitzel, Copenhagen.

Shigei, M. 1986. The sea urchins of Sagami Bay. Maruzen Co., Tokyo