The National Academy of Sciences of Tajikistan, Institute of Geology, Earthquake Engineering and Seismology, Ainy-street 267; 734063 Dushanbe, Tajikistan.
Abstract: The symmetry as morphological feature of Paleozoic corals can have in some cases taxonomic value, in other cases it is considered only as an integral characteristic of the population. Symmetry of corallites is evaluated by the shape of their cross section, but the number and location of septa can also be taken into account. Symmetry of corallites of the Tabulata, Heliolitida and Rugosa can change not only at different representatives, but also in the astogenesis of the same colony or in the ontogenesis of solitary forms. Talking about the symmetry of corallites in massive colonies is possible only if their sides are equal. By analogy with the cellular structures of biological tissues, the term “corallite adjacency” for massive colonies is proposed. The formation of the main types of symmetry of Paleozoic corals is inseparably linked with the origin of these groups. The small sizes of the ancient initial forms prove that not adult polyps were subjected to calcification. Larvae or planula-like organisms, representing a reduced stage of development of Corallomedusa (pedomorphosis), settled to the bottom and gave rise to the first calcite polyps, which were bent by their own weight or sea currents. The early coloniality of heliolitids could be associated with the subsidence of a group of genetically homogeneous planules, unlike the Rugosa and Tabulata. Shafranovsky has developed the Curie symmetry principle, indicating that the elements of the organism’s symmetry may not fully coincide with the symmetry of the environment or may not coincide with it. Symmetry of corallites and colonies of Paleozoic corals is connected with symmetry of the gravity. A phylogenetic implication shows that tetragonal symmetry is the most ancient and was inherent in the ancestors of corals. We should take into account the rule of Shafranovsky (everything that grows and moves horizontally and obliquely has bilateral symmetry; everything that, being attached, grows vertically, has radial symmetry) studying coral symmetry.
Keywords: Paleosclerocoralla, auloporoidity, calcification, septogenesis, phylogeny, Shafranovsky’s rule.
Pages: 256 – 269 | Full PDF Paper