Detailed biostratigraphic scales as based on the palaeobiogenetical approach (an example of the Upper Bajocian – Lower Bathonian ostracod scale of the Russian Platform)

Two new species of ostracods of the family Progonocytheridae Sylvester-Bradley Camptocythere (C.) lateres Tesakova et Shurupova, sp. nov. and C. (C.) angustius Tesakova et Shurupova, sp. nov. from the Michalskii and Besnosovi ammonite zones (Upper Bajocian – Lower Bathonian, Middle Jurassic) of the Sokur section (Saratov) are described. The changes in ontogenesis in the phylogeny of Camptocythere (C.) lateres Tesakova et Shurupova in the stratigraphical interval corresponding to the Palaeocytheridea kalandadzei ostracod Zone, and especially to the beds with C. (C.) lateres, have been studied. The levels of the change in the predominant type of sculpture (corresponding to evolutionary boundaries) are recognized in the sculpture development among the adult representatives of the species in its phylogeny. This palaeobiogenetic (heterochrony) approach allows subdivision of the beds with C. (C.) lateres into three stratigrapical intervals characterized by changes in the type of sculpture.