Izvestiya of Saratov University.
ISSN 1819-7663 (Print)
ISSN 2542-1921 (Online)

поздний мел

Colonial Level of Modular Organization in the Late Cretaceous Hexactinellids (Porifera). Primary Colonies

In the structure of modular organization of the Late Cretaceous hexactinellid sponges, the terminal position is assigned to colonial forms, with skeletons peculiar for complex, intricate structures. Primitive (primary) and genuine (secondary) colonies have been revealed. Skeletons of the primary forms, generally with multiple numbers of equivalent modules and oscula, differ morphologically from the genuine colonies in undeveloped module connecting elements, such as junctions and wall closures, and in the lack of ostia


The Late Cretaceous Deposits of Potassium Soils at the Gremyachinsk Field

The authors consider the compound of the late cretaceous deposits opened up in the bore hole number 13, 62 at the Gremyachinsk field of the potassium soils in the Volgograd region. According to the sediment basins evolution from the epicontinental basins (cenoman, turon-cognacian) to the subpelagic basins (cenonian) the lithotipe which form in the late cretaceous level the regular repeated layers of the terrigenous, carbonate, argillaceous-siliceous deposits are characterized

Neogenesis in Structure of Skeletons of Late Cretaceous Sponges Contributed to the Formation of Polyosculumic Forms

Arterial directions in formation of module organization of skeleton hexactinellids are caused by vegetative forms of reproduction. It is supposed that some tendency of selection of protozoa module forms can be traced in morphogenesis of separate generic types of late Cretaceous sponges. The concept “polyosculumic„ sponges is considered in vast context personally in reference to skeletons with some osculumics formed in the result of partial regeneration of organism

Colonial Level of Modular Organization in the Late Cretaceous Hexactinellids (Porifera). Genuine Colonies

Tendencies of morphogenesis in the Late Cretaceous modular forms contributed to formations of complexly structured secondary (genuine) colonies. Skeletons of genuine colonial sponges differ not just in numerous and diversely arranged equivalent oscula-carrying modules, but in the presence of the module connecting elements – junctions, as well. Characteristic elements of genuine colony skeletons – ostia – have been recognized between the modules and the junctions.

Regenerative Capabilities in the Late Cretaceous Hexactinellids (Porifera, Hexactinellida)

Partial and complete regeneration phenomena, cases of skeleton habitus restoration have been recorded in representatives of the Late Cretaceous hexactinnelids. Regeneration incidences are in many ways associated with the ability of silicon-producing cells responsible for constructing skeleton-generating elements, spicules, to transform, to rearrange their functions in response to the changes of the organism position on the substrate surface and/or upon the changes of the aquatic environment parameters.

Morphogeneses of the Late Cretaceous Guettardiscyphia (Porifera, Hexactinellida)

Guettardiscyphia skeletons are peculiar for thin walls and highly dense apo- and prosopores. Wall mobility was conductive to formation of conical lobate skeletons of various, occasionally geometrically regular outlines. Substantial number of fossil samples from variously composed rocks from all the Upper Cretaceous intervals has made it possible to trace skeleton transformations in sponge ontogenesis and depending on their environmental conditions.

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

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.

Morphotypes of the Late Cretaceous Hexactinellids (Porifera, Hexactinellida)

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.

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.

Demonstration of Gemmation among Cretaceous Skeletal Sponges – Hexactinellida

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.