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Bryozoa
Schizomavella auriculata (Hassall, 1842)
Nomenclature
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Family: BitectiporidaeGenus: Schizomavella
- holotype: B.M.(N.H.) Palaeont. Dept. B1678
SUMMARY
Colonies are multiserial, forming encrusting sheets, unilamellar or multilamellar. The ancestrula is overgrown by frontally budded zooids in the studied specimen from the Coralline Crag. Zooids from early astogeny have 4 oral spine bases.
Autozooids are significantly longer than wide, measuring about 0.30-0.48 mm long by 0.26-0.41 mm wide, subrectangular in outline shape with a concave proximal and convex distal edge, and are separated by deep grooves. Frontal shields preserving the outer aragonitic layer are rugose with coarse nodules but smooth when this layer has been lost. They are evenly perforated by pseudopores, and have a border of more elongate areolar pores. A prominent umbo is present. The orifice is small, slightly longer than broad, measuring about 0.08-0.09 mm long by 0.07-0.08 mm wide, somewhat inclined in a plane relative to the frontal surface, with a shallow U-shaped sinus. Condyles are distinctive in Recent material, longer than wide, not extending to the margins of the sinus and have a cuspate distal edge (fide Hayward & Ryland 1999, p. 276). Oral spines generally number 3 in Crag material. Ovicells in Recent colonies are flattened frontally with up to 20 irregular pores in the ectooecium, overgrown by secondary calcification encroaching from the edges (Hayward & Ryland 1999).
Adventitious avicularia are borne by all autozooids and are located suborally between the umbo and the proximal edge of the orifice. They are longer than wide, measuring about 0.10 mm long by 0.05 mm wide, directed proximally and inclined at a high angle to the colony surface. The rostrum is rounded triangular in shape and the crossbar calcified.