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

module organization

Transitory Level of Modular Organization in the Late Cretaceous Hexactinellids (Porifera)

The regularly arranged openings acting as additional oscula – subos­cula – in the skeletal structures of numerous hexactinellids made the basis for recognizing a transient level in those sponge organization: a transition between the unitary and the colonial forms. Unitary, autono­mous and colonial sublevels have been recognized in the transition structures. The morphological diversity of the Late Cretaceous transi­tions was called forth by manifestations of mosaic morphogenesis in the representatives of the Lychniscosa and Hexactinosa orders.

Module Organization in the Late Cretaceous Hexactinellids (Hexactinellida, Porifera)

Knowledge on the regularities of vegetative propagation and comprehension of the osculum (oscula) and subosculum structural-functional positions and interrelations in the skeleton structure have made it possible to specify the organization levels in the Late Cretaceous hexactinellids: the unitary (solitary, perifrontal and autonomous forms), transitory (solitary, autonomous and colonial forms) and colonial (primary and true colonies) ones.