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Diagnostic Features
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- Test small, composed of relatively thin, imbricate plates; shape unknown.
- Periproct a mass of small plates.
- Five ambulacral and five interambulacral zones. Ambulacral zones composed of a single perradial column of hexagonal plates bounded on either side by subrectangular plates that are perforated by a single slit-like opening.
- Radial water vessel presumed internal; small perradial flanges to the perforate plate but these do not meet to fully enclose the water vessel.
- Perforate plates with a small non-mamelonate granule on either side of the perforation.
- Interambulacral zones uniserial towards apex, biserial at ambitus; with small, scattered granules covering plates but no tubercles.
- Peristome small; plating unknown.
- Lantern structure unknown.
- Spines small straight and simple, confined to ambulacral plates.
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Distribution
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Burrellian, Early Caradoc, Middle Ordovician of Oklahoma, USA. |
| Name gender |
masculine |
| Type |
Bromidechinus rimaporus Smith & Savill, 2001, p. 141 by original designation. |
| Species Included |
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| Classification and/or Status |
Stem group Echinoidea; unnamed plesion.
Monotypic.
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| Remarks |
The plating structure in Bromidechinus is similar to that seen in ophiocistioids and Smith & Savill (2001) place this as the most primitive known echinoid.
Smith, A.B. & Savill, J. J. 2001. Bromidechinus, a new Middle Ordovician Echinozoa (Echinodermata), and its bearing on the early history of echinoids. Transactions of the Royal Society of Edinburgh 91, 137-147.
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