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 for the first time described. 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) и Cerioporina (6 taxa). Due to 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 reflected. The assemblage includes the taxa that have the similarities 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 in having bryozoans from the family of Eleidae, but it differs from the Barremian assemblage of France in lacking of representatives of Cheilostomata. Among the studied cyclostomes, bryozoans with erect colonies predominate, some of which were 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.