clava d'Orbigny, 1853, p. 889
Cretaceous, Cenomanian, Villers, France
Type: MNHN R61535 d'Orbigny Collection
colony erect, dendroid, narrow-branched, branch width increasing where gonozooid is present
autozooids free-walled; apertures subcircular, evenly-spaced
kenozooids numerous, free-walled, totally surrounding the autozooids; apertural diameter half or less that of autozooids
gonozooid fixed-walled, dendritic, occupying space normally filled by kenozooids, the roof slightly depressed where not removed by erosion
D'Orbigny's first description of Claviclausa clava appeared on p. 890 of the Terrains Crétacé, published in 1853. However, he had previously figured the species as Entalophora clava on plate 620 of the Terrains Crétacé which may date from as early as 1851, although the exact dates of publication of the Terrains Crétacé plates are unknown. The two large scale specimens depicted in plate 620 are clearly different species - that shown in figure 6 corresponds more closely with both the type specimen and Claviclausa clava as later figured by d'Orbigny on plate 765, fig. 5, whereas the other specimen appears to be a dendroid tubuliporine with a slightly clavate branch.
Walter et al. (1975, pl. 10, fig. 9) refigured the specimen in the d'Orbigny Collection which had been separated as the putative type (lectotype) of Claviclausa clava. They placed this species in synonymy with Clausa heteropora, the type species of Clausa, thereby making the genus Claviclausa a junior synonym of Clausa. The most striking difference between the two species evident from the respective type specimens is in the skeletal organization of the zooids - these have calcified exterior walls in Clausa micropora (i.e. fixed-walled) but lack such walls in Claviclausa clava (i.e. free-walled). This difference may, however, be relatively unimportant and caused by ontogenetic variations like those described by Ross (1973) in the extant cyclostome Heteropora.
Orbigny, A. d' 1851-1854. Paléontologie Française, Terrains Crétacé, 5, Bryozoaires. Masson, Paris, 1192 pp, pls 600-800.
Ross, J.R.P. 1973. Calcification in the colonial stenolaemate, Heteropora. In: Larwood, G.P. (ed.) Living and Fossil Bryozoa, Academic Press, London, pp. 475-483.
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.