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Clausa d'Orbigny, 1853


D'Orbigny's illustrations of Clausa heteropora.
Scanning electron micrograph of branch of Clausa heteropora. Scanning electron micrograph of zooids of Clausa heteropora. Scanning electron micrograph of Clausa heteropora showing growth tip. Scanning electron micrograph of slender branch of Clausa heteropora.
Scanning electron micrograph of Clausa heteropora showing open autozooidal apertures and kanozooids closed by diaphragms. Scanning electron micrograph of Clausa heteropora showing lobes of gonozooidal frontal wall. Scanning electron micrograph of growing tip of Clause heteropora. Scanning electron micrograph of autozooids in Clausa heteropora.

Type species

Ceriopora heteropora d'Orbigny, 1850, p. 184
Cretaceous, Cenomanian, Le Mans, Sarthe, France

?Syntype material: MNHN R61539, d'Orbigny Collection



Diagnostic features

  • colony erect, comprising slender cylindrical branches expanding in width distally and becoming club-shaped

  • autozooids fixed- or free-walled; in one ?syntype (R61539a), free-walled within a narrow zone proximal of the growing tip, then fixed-walled and lacking a frontal wall but with short collar-like peristomes; in the second ?syntype (R61539b), fixed-walled (except where abraded) and with pseudoporous frontal walls.

  • kenozooids numerous, fixed- or free-walled in R61539a polygonal, closed by slightly depressed terminal diaphragms, and surrounding the apertures of the autozooids, in R61539b fixed-walled, somewhat elongate and interspersed among the autozooids

  • gonozooid in R61539a fixed-walled, lobate, with finger-like distal extensions extending between the autozooids and filling space otherwise occupied by kenozooids, frontal wall sunken beneath level of autozooids; R61539b lacks a gonozooid


Classification

Order Cyclostomata
Suborder Cerioporina
Family Clausidae



Remarks

Gregory (1899, p. 408) selected the type species of Clausa from among the nine species listed in this genus by d'Orbigny (1853, pp. 893-898). Material of C. heteropora in the d'Orbigny Collection comprises more than one species and none of it matches well enough with his figures to be confident that it corresponds with the species he described in 1850 and which became the type of his 1853 genus Clausa. The putative syntype numbered R61539a, which was refigured by Walter et al. (1975, pl. 10, fig. 10) is the better match of the two species depicted here and may provisionally serve as a basis for understanding the genus. This specimen is similar to a specimen from Uzbekistan figured by Voigt (1967, pl. 32, fig. 5) as Clausa heteropora, whereas the other 'syntype' resembles Clinopora.

Clausa is the type genus of d'Orbigny's family Clausidae.



References

Gregory, J.W. 1899. Catalogue of the Fossil Bryozoa in the Department of Geology, British Museum (Natural History). The Cretaceous Bryozoa. Volume 1. BM (NH), London, 457 pp.

Orbigny, A. d' 1850. Prodrome de Paléontologie Stratigraphique Universelle des Animaux Mollusques et Rayonnés faisant suite au cours élémentaire de Paléontologie. Tome 1. Masson, Paris.

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

Voigt, E. 1967. Oberkreide-Bryozoen aus den asiatischen Gebieten der UdSSR. Mitteilungen aus dem Geologisch-Staatinstitut der Universität Hamburg, 36: 5-95.

Walter, B., Arnaud-Vanneau, A., Arnaud, H., Busnardo, R. and Ferry, S. 1975. Les Bryozoaires Barrémo-Aptiens du sud-est de la France. Gisements et paléoécologie, biostratigraphie. Geobios 8: 83-117.