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Bicrisina d'Orbigny, 1853

D'Orbigny's figures of Bicrisina cultrata. D'Orbigny's figures of Bicrisina cultrata.
Scanning electron micrograph of branch of Bicrisina cultrata in lateral view. Scanning electron micrograph of gonozooid of Bicrisina cultrata. Scanning electron micrograph of Bicrisina cultrata showing rows of autozooids separated by kenozooids.

Type species

Bicrisina cultrata d'Orbigny, 1850, p. 265
Cretaceous, 'Senonian', Pérignac, France

Type material: MNHN d'Orbigny Collection 8329 (8 fragments; note, this putative type material is labelled 'Royan')


Diagnostic features

  • colony erect, reticuliporiform, comprising bifoliate branches ovoidal in transverse section, with distinct frontal and reverse sides, the former distinguished by the presence of a growing edge

  • autozooids free-walled (lacking calcified exterior walls) having elliptical apertures arranged in curved connate rows along branch sides

  • kenozooids free-walled, occupying areas between autozooidal rows, their walls thickened to form ridges aligned parallel to branch long axes and their apertures depressed

  • gonozooids fixed-walled, located on the side of the branches, ovoidal in outline shape, the frontal wall penetrated by occasional autozooidal apertures


Classification

Order Cyclostomata
Suborder Cerioporina
Family Incertae Sedis


Remarks

The reticuliporiform (or 'eccentric bifoliate') colony-form found in Bicrisina is characteristic of several Mesozoic cyclostome genera, including Reticulipora Retenoa, Retelea, Reticrisina and Retecava. Further research is necessary to establish the validity and familial affinities of these genera. Bicrisina has a cerioporine grade of skeletal organisation, i.e. with free-walled autozoooids (and kenozooids) but fixed-walled gonozooids.


References

Orbigny, A. d' 1850-1852. Prodrome de Paléontologie Stratigraphique Universelle des Animaux Mollusques et Rayonnés faisant suite au cours elémentaire de Paléontologie. Masson, Paris (3 volumes).

Orbigny, A. d' 1851-1854. Paléontologie Française, Terrains Crétacé, 5, Bryozoaires. Masson, Paris, 1192 pp, pls 600-800.