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Bryozoa
Copidozoum? aperta (Busk, 1859)
Nomenclature
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Family: CalloporidaeGenus: Copidozoum
- holotype: B.M.(N.H.) Palaeont. Dept. B1638
SUMMARY
The colony is multiserial, forming an encrusting, unilamellar sheet. Early astogeny is unknown.
Autozooids are slender, large, about 0.60-0.70 mm long by 0.17-0.25 mm wide, and typically rhomboidal in outline shape. Most of the frontal surface is occupied by the opesia which is elliptical in shape. Gymnocyst is lacking and the cryptocyst is restricted to a very narrow, smooth wall sloping steeply inwards around the perimeter of the opesia. Spines are lacking. Ovicells have not been observed. Basal walls of the zooids are uncalcified, or perhaps were aragonitic and lost during fossilization.
Vicarious avicularia are very common, some but not all associated with row bifurcations. Often two or more avicularia follow one another in linear series. Most avicularia are large, about the same length as an autozooid or slightly shorter, but significantly narrower, and acuminate. The opesia is hemielliptical, longer than wide, its distal limit defined by the calcified pivotal bar which is deep and has a downward-sloping distal face. The rostrum is overall spearhead-shaped, constricted at its sides by infoldings of the lateral gymnocyst, and has the form of a gothic arch distally where a moderate palate is developed.