ИСТИНА

In the period from 1985 to 1993 B.B. Nazarov and A. Ormiston described from the Upper Carboniferous and Lower Permian sediments of the Southern Urals a number of species of radiolarians with unusual polyhedral skeletal shape, assigned to the genus Polyentactinia Foreman, 1963. However, in 1989, H. Kozur and H. Mostler from the Sakmarian Stage described a new genus Polyedroentactinia with the type species P. cisuralica Kozur et Mostler, 1989. The general plan of the skeleton structure of this genus coincides with that of species of Nazarov and Ormiston. In recent years, several articles have been published on the revision of the genus Polyentactinia, according to which a number of its species were transferred to the genus Polyedroentactinia. Eleven species can be assigned to the genus Polyedroentactinia. It is proposed to divide them into three morphological groups. Species belonging to the first group are characterized by the presence of well-defined segments, thin partitions between them and the presence of numerous pores in each segment. Representatives of the second group have indistinctly expressed segments with very thin partitions between them and the absence of any porous shell in the segments. Species of the third group have well-defined segments with thick partitions between them and absence of any porous shell in them. Judging by the stratigraphic distribution, all groups evolved almost equally throughout the Late Carboniferous-Late Permian. However, representatives of the second group, despite the simplest skeletal structure, have the shortest distribution time and, relative to other groups, existed only at the end of the Early and beginning of the Middle Permian. This is probably due to their adaptation to specific environmental conditions. The species Polyedroentactinia fiscina (Nazarov et Ormiston) and P. cisuralica Kozur et Mostler, having the same skeletal structure, were published in 1989, but the article describing P. cisuralica Kozur et Mostler went out of print several months earlier, so the latter name has priority.