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The Echinoid Directory

Opechinus Desor, 1856, p. 107

[=Pseudopechinus Lambert & Thiery, 1911, p. 232 (objective); =  Trumechinus Lambert & Thiery, 1911, p. 216, type species Trumechinus batheri Lambert & Thiery, 1911, p. 216 (=Temnopleurus rousseaui d'Archiac & Haime, 1853); =Sphaeropleurus Markov & Endelman, 1991, p. 80, type species Sphaeropleurus geometricus Markov & Endelman, 1991]

Diagnostic Features
  • Test somewhat inflated with rounded ambitus; flattened above and below.
  • Apical disc dicyclic with circular periproct; genital plates with a ring of tubercles surrounding periproct. In living members a suranal plate weakly differentiated.
  • Ambulacra straight and wide; pore-pairs more or less uniserial throughout. Plating trigeminate, compound in echinid-style. Pore-pairs more or less uinserial throughout; not expanded adorally.
  • Small primary tubercle on each compound plate close to pore zone and double column of deep wedge-shaped sutural pits alternating up the perradius.
  • Interambulacral plates only moderately wide with single primary tubercle centrally placed. Primary tubercles in column connected by vertical ridge.
  • Large wedge-shaped sutural pits well developed plus small interradial pits at all triple suture points. Sometimes pits on interradial side of primary tubercle. Trapezoidal raised areas on adradial and interradial sides of the primary tubercle bearing small miliaries and granules.
  • Tubercles imperforate and non-crenulate.
  • Peristome deeply sunken, with almost no buccal notches.
  • Lantern and spines unknown in type species.
Distribution
Eocene to Recent, Pakistan, India, Malaysia, Indonesia, Indo-West Pacific.
Name gender masculine
Type
Temnopleurus costatus d\'Archiac & Haime, 1853, p. 204, by subsequent designation of Pomel, 1883, p. 85.
Classification and/or Status
Euechinoidea; Camarodonta; Temnopleuroida; Temnopleuridae.
Remarks

Distinguished from Temnotrema only really by the form of the sutural pits. In Opechinus the pits on interambulacral plates are largest immediately beside the primary tubercle and narrow towards the adradial and interradial sutures, often with smaller secondary pits adradially and interradially. In Temnotrema the pits are more or less parallel sided top and bottom, and multiple pits are absent.

Some species of Toreumatica have similar wedge-shaped pits, but their primary tubercles are distinctly crenulate. Sphaeroopleurus has similar large pits, but its ambulacral plating is glyphocyphid, not echinid in style.

Desor, E. 1858. Synopsis des échinides fossiles, lxviii + 490 pp., 44 pls. Reinwald, Paris.

Lambert, J. & Jeannet, A. 1935. Contribution a l\'etude des Echinides tertiaires des Iles de la Sonde. Memoires de la Societe paleontologique Suisse 56, 1-62, pls 1-4.

Mortensen, T. (1943) A monograph of the Echinoidea Part III.2, Camarodonta 1. C. A. Reitzel, Copenhagen.