Uppermost Carboniferous (Kasimovian-Gzhelian) successions from the Middle Tien-Shan are composed of over 1500 m of terrigenous and carbonate strata. The lower part of the stratigraphic section is conglomeratic and forms the 500-m-thick Minbuginskaja suite. The upper part consists of 1000 m of interbedded terrigenous and carbonate beds of the Kodzhagulskaja suite. Fossils (e.g., foraminifers, brachiopods, ammonoids, mollusks and algae) are abundant in the Kodzhagulskaja suite, but only fusulinoideans occur consistently throughout the studied sections and enable the establishment of a biostratigraphic zonation. Although fusulinoidean assemblages from the Middle Tien-Shan contain many endemic species, the presence of several more widely-distributed forms has enabled interregional correlations.
A new genus, Pseudodaixinoides, and 38 other new species are described: Quasifusulina akbeitica, Q. kodzhagulica, Q. ptchanica, Triticites proprius, T. kodzhagulicus, T. nitidus, T. fusinus, T. procerulus, T. polinae, T. ornatus*, T. oblisus, T. komansuensis*, T. komansuensis deplanatus, Jigulites altus kodzhagulensis, Schwageriniformis mundulus, S. planus*, S. cuneatus*, S. tianshanicus*, S. arpaensis, S. kalcagarensis*, S. anosovae, S. magnificus, Pseudodaixinoides kalcagaricus, P. honestus*, P. cincinnatus*, P. septiplicatus*, P. cylindricus, P. pseudoartensis*, P. admirandus, P. cucumeriformis, P. quasiplanus, Kahlerella kirgisica*, Dutkevitchia oblonga*, Daixina (Daixina) porrecta, D. (D.) kodzhagulica, Daixina (Bosbytauella) akbeitica* and Pseudofusulinoides akbeiticus. The new genus, Pseudodaixinoides, includes nine new species from the above list. The 13 species that are marked with an asterisk (*) were described by N. A. Anosova (manuscript) in 1952 but are based on only a single specimen. Moreover, she did not study their stratigraphic distribution. Thus, we think it is necessary to consider N. A. Anosova as one of authors of the species, but not as one of the authors of this study.
Study, identification and description of species are fundamental to definition of stratigraphic subdivisions (i.e., formations and beds). The widespread occurrence of fusulinid assemblages in all types of lithologies makes it possible to reconstruct regional paleoenvironments and paleogeography and set them into the general geological scheme of the Carboniferous of Eurasia.