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The first representatives of the genus Cameroptychium Leonhard, 1897 (Porifera, Hexactinellida) from the Upper Cretaceous of the Volga region

Authors: Pervushov E. M.

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.

Representatives of the genus Botryosella Schrammen, 1912 (Porifera, Hexactinellida) from the Upper Cretaceous of the Volga region

Authors: Pervushov E. M.

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.

Colonial Leptophragmidae (Porifera, Hexactinellida) from the Lower Santonian of the Volga region

Authors: Pervushov E. M.

Study of the skeletal morphology of a new representative of the Leptophragmidae family, with no suboscula in its structure, provides support for the earlier specified regularities in generation of Hexactinellida modular forms. Good preservation state of a major colony has made it possible to specify the aspects of paleoecology and taphonomy in the later representatives of the Middle Coniacian – Early Santonian succession of siliceous sponges.

Pseudoderivations of Paracraticularia cylindrica (Michelin, 1840) (Porifera, Hexactinellida)

Authors: Pervushov E. M.

The morphological diversity of diosculumic sponges, known as Paracraticularia cylindrical, results from the fact that many fossils assigned to this species prove to be fragments of the apical segments of internodes (branches) from major colonies that are rarely encountered as totally preserved fossils. The structures of the branch apical segments and the oscula outlines reflect various manifestations of hexactinellida synchronous division conductive to morphological diversity of the descendants, the succeeding complicatedly structured colonial sponges.

Contubernium Ochevi (Porifera, Hexactinellida)

Authors: Pervushov E. M.

Among the Late Cretaceous Ventriculitidae, with the most simply constructed pariform skeleton, representatives characterized by unusual neoplasms were identified. On the paragastric surface after the lapel of these sponges (Contubernium), cone-shaped submodules are regularly based, the appearance of which is associated with incomplete blastogenesis. Paragastra of submodules are not associated with the atrium, therefore, Contubernium is considered as a perifrontal organism, occupying an intermediate position between single and modular forms of spongia.

Composition and Structure of the Ventriculitidae (Porifera, Hexactinellida) Family

The Ventriculitidae representatives used to hold noticeable and occasionally dominant position within the Coniacian – Maastrichtian sponge assemblages. Relatively simple skeleton construction in the representatives of the family among the Late Cretaceous hexactinellids has made it possible to trace variations in skeleton morphology, changes in the goblet habitus and in the structure of irrigation system depending on the width variations of the skeleton-building wall.

Demonstration of Gemmation among Cretaceous Skeletal Sponges – Hexactinellida

Authors: Pervushov E. M.

The examination of the modular organization in fossil skeletal sponges (Hexactinellida) is mainly related to a study of their vegetative reproduction. The concepts of the reproductive forms for both Recent and Mesozoic hexactinellids can be ambiguous. Examples of the skeletons of fossil sponges from the Late Cretaceous of the Volga River basin, with morphologically detached and naturally distributed sprouts interpreted as buds, are shown. 

On the Genus Balantionella Schrammen, 1902 (Porifera, Hexactinellida)

The Balantionella genus has been recognized by A. Schrammen (1902) from a single specimen and two skeleton fragments from a locality in the «quadrate» Cretaceous rocks in Germany. In the southeast of the Russian Plate, representatives of the genus have been determined within units from all the stages of the Upper Cretaceous. This has made it possible to provide characteristics and to trace the morphogenetic tendencies in the representatives of the group. Three subgenera and 12 species have been recognized.

Morphotypes of the Late Cretaceous Hexactinellids (Porifera, Hexactinellida)

Authors: Pervushov E. M.

Basic structure types have been specified in hexacinellids with soldered spicule lattice. The fossils of those occur as skeletal forms. Certain tendencies in Lychniscosa and Hexactinosa morphogenesis were identified as conductive to shaping the spectrum of skeleton archetypes. The increase of sponge morphological diversity was in many ways predetermined by thickness reduction of the skeleton-forming walls, associated with reduction of the irrigation system elements. That has brought about forms of complicated tubular labyrinth habits.

Representatives of the Genus Camerospongia (Porifera, Hexactinellida) from the Cenomanian in the Volga Region

Authors: Pervushov E. M.

The earliest assemblage of Cretaceous sponges has been found in the Cenomanian terrigenous rocks (the Melovatka suite) from the south of the Volga right bank region. A noticeable element of the assemblage is composed of small-sized Camerospongia, newly recognized in the region and peculiar for forming monotype colonies as well.

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