sponges

The first representatives of Cameroptychium on the territory of Russia, which are established in the rocks of the Upper Cretaceous of the Volga region, are described. The labyrinthine structure of the skeleton and the modular, colonial level of organization of these sponges are considered, which is typical for many Late Cretaceous Hexactinellids. The widespread manifestation of isomorphism indicates the finiteness of the formation of representatives of Hexactinellida. The origin of Cameroptychium is correlated with Santonian Plocoscyphia.

Among the numerous and diversiform Late Cretaceous siliceous sponges collected throughout the Volga region, several representatives of the genus Botryosella have been encountered, previously unknown for the area. Analysis of the skeleton morphology, peculiar for massive transverse outgrowths, confirms manifestations of isomorphism in Hexactinellids and the opinion of inaccuracies available in the descriptive terminology applied to the skeletal morphology of this Porifera group.