Taxonomic Composition of the Hauterivian Bryozoan Assemblage in the Environs of Gunib Village (Dagestan).

The Lower Cretaceous bryozoan assemblage in the environs of Gunib village in Dagestan is described for the first time. The studied section is located in the zone of development of the Gapshima Formation (Hauterivian) deposits. The bryozoan assemblage is characterized by high taxonomic diversity and includes 32 taxa from four suborders of order Cyclostomata: Tubuliporina (24 taxa), Cancellata (1 taxon), Articulina (1 taxon), and Cerioporina (6 taxa). Because of the poor preservation of the colonies, most taxa are defined in open nomenclature. Therefore, the true diversity of cyclostomes in the study area is not fully recognized. The assemblage includes the taxa which are similar to bryozoans previously described from different levels from Valanginian to Barremian of Switzerland and France and, partly, from the lower Hauterivian of Germany (Mecynoecia icaunensis (d'Orbigny), Mesenteripora marginata (d'Orbigny), M. reticulata (d'Orbigny), Poriceata ardescensis Walter, Apsendesia neocomiensis d'Orbigny, Diplocava biformis (Roemer), "Heteropora" arborea Koch et Dunker, and Elea periallos Taylor). The main difference of the Gunib assemblage from the Valanginian–Hauterivian assemblage of Switzerland and France and the lower Hauterivian assemblage of Germany is the presence of bryozoans from the family Eleidae, but it differs from the Barremian assemblage of France in the absence of Cheilostomata representatives. Among the studied cyclostomes, bryozoans with vertically growing colonies predominate. Some of these bryozoans are bilateral leaf-shaped, while others had thin cylindrical branches. Reticulate and massive colonies are rare, while encrusting bryozoans, which grow over erect colonies, are quite numerous. [ABSTRACT FROM AUTHOR]