The Echinoid Directory

• Test large with moderately thin plates. Sutures imbricate.
• Apical disc unknown in type species.
• Ambulacra basically trigeminate but with a larger primary tubercle on every second or third compound plate, making adoral plating appear polygeminate. Trigeminate plates composed of a single large element and two small demiplates.
• All three elements of a compound plate in contact with adradial suture throughout.
• Pore-pairs forming a broad adradial zone adorally.
• Interambulacral plates wide, with row of three subequal primary tubercles.
• Primary tubercles occupying full plate height; perforate and non-crenulate.
• Peristome with columns of ambulacral plates only.
• Oral spines with spongy stereom fill and without hyaline hoof.
• Tridentate and ophicephalous pedicellariae present.

Oxfordian, Late Jurassic; Europe.

Hemipedina corallina Wright, 1858, by original designation.

• P. corallina (Wright, 1858); Oxfordian, Upper Jurassic, UK.
• P. oolithicum (Hess, 1972); Bajocian, Middle Jurassic, Switzerland.

Euechinoidea; Echinothurioida; Pelanechinidae.

?Paraphyletic.

Only the oral surface of the type species of this taxon is known at present. However a second species, P. oolithicum, is much better known. The well developed adoral phyllodes with trigeminate compound plates of various sizes that form composite plates, and the quadriserial ambulacral plating on the peristome help to distinguish Pelanechinus from other echinothurioids.

Groom, T. T. 1887. On some new features in Pelanechinus corallinus. Quarterly Journal of the Geological Society of London 43, 703-714.

Keeping, W. 1878. On Pelanechinus, a new genus of sea-urchin from the Coral Rag. Quarterly Journal of the Geological Society of London 34, 924-930.