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Bisidmonea d'Orbigny, 1853


D'Ornigny's illustration of Bisidmonea antiqua.
Scanning electron micrograph of branching fragment of a Bisidmonea antiqua colony. Scanning electron micrograph of a branch of a colony of Bisidmonea antiqua. Scanning electron micrograph of a group of autozooids of Bisdimonea antiqua.


Type species

Bisidmonea antiqua d'Orbigny, 1853, p. 720
Jurassic, Bathonian, Ranville, France; subjective junior synonym of Spiropora tetragona Lamouroux, 1821

Type material: MNHN d'Orbigny Collection 2952; listed as the 'type' by Walter (1970, p. 218)



Diagnostic features

  • colony erect, dendroid, consisting of narrow bifurcating branches with a rounded quadrate cross-section

  • autozooids fixed-walled, short, polygonal in outline, with boundary walls prominent on the colony surface; apertures circular or transversely elliptical, arranged quincuncially or in ill-defined, non-connate transverse rows, and often closed by terminal diaphragms

  • kenozooids fixed-walled, infrequent

  • gonozooid lacking in type, simple and longitudinally elongate in non-d'Orbigny material


Classification

Order Cyclostomata
Suborder Tubuliporina
Family Multisparsidae



Remarks

The type species of Bisidmonea is considered to be a junior synonym of Spiropora tetragona Lamouroux, 1821 by Walter (1970). This multisparsid cyclostome has dendroid colonies resembling Collapora (not to be confused with the cheilostome Callopora) but in Bisidmonea the branches have a rounded quadrate cross-section, exaggerated by d'Orbigny in his figures. Gonozooids, which are lacking in the type material of B. antiqua, are simple, longitudinally elongate, may cross from one side of a quadrate branch to another, and have transversely elliptical ooeciopores about the same size as the autozooidal apertures. It is uncertain whether the genus, which may be monospecific, ranges beyond the Jurassic. Although Brood (1970) described a Recent species as Bisidmonea azorica, this extant species is not closely related to the Jurassic type species. Instead, B. azorica appears to belong to the Tubuliporidae - the autozooidal apertures are arranged in connate rows, with a lobate gonozooid extending between these rows and having a narrow ooeciostome adnate to the distal face of an autozooidal peristome.



References

Brood, K. 1970. Bisidmonea azorica n.sp., a modern species of Bisidmonea. Stockholm Contributions in Geology 21, 53-55, 1 pl.

Lamouroux, J. 1821. Exposition méthodique des genres de l'ordre des Polypiers. Agasse, paris, 115 pp., 84 pls.

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

Walter, B. 1970. Les bryozoaires jurassiques en France. Documents des Laboratoires de Géologie de la Faculté des Sciences de Lyon 35 [for 1969], 1-328.