Recent data on systematics of Polymorphinidae family of Campanian-Maastrichtian foraminifers of Western Siberia

Thematerial obtained from the boreholes of the south-eastern district of Western Siberia enabled to establish new taxa (species andsubspecies) in the Polymorphinidae Family. The descriptions of the Polymorphinidae taxa made by the author were based on fivecriteria (morphological, geochronological, palaeogeographic, palaeobiogeographic, and the criterion of discreteness) proposed byA.V. Fursenko (1978). One species and two subspecies are described from the deposits of the Gankinskaya Suite. Lithologically, thesuite is composed of rather monotonous, gray compact siltstone and clays. The character of porosity in the studied Polymorphinidae maybe subdivided into two types. The first type is the most widespread; this is the porous surface of the shell penetrated by the smallest spotholes with the size of 0.3-0.5 μm. The form of the holes is close to rounded; it is quite constant; pores are located unevenly or chainlike.Pores are simple: they are immarginate and are characteristic for numerous species assigned to the genera of Glandulina,Eoguttulina, Pyrulina, Sigmomorphina, Guttulina, Globulina, Ramulina. The taxa with the pores of the second type were notencountered. For establishing the species and subspecies categories, the morphological, geochronological and paleogeographic criteriawere mainly applied. In comparing the known species described by Kuzina (1976), the author revealed an obvious disagreement indetermining their age. So, with regard to the above-stated criteria, it was possible to distinguish new taxa among Polymorphinidae. Indescribing species and subspecies, their alternative stratigraphic position and age were defined, which differs from those establishedpreviously. The finds of the Guttulina lidiae Vassilenko Species are dated back to the Palaeocene according to Kuzina's report (1976).From this standpoint, the Siberian subspecies of this species was established: Guttulina lidiae Vassilenko subsp. sibirica Kseneva of theUpper Campanian and Maastrichtian deposits (the Gankinskaya Suite). This subspecies shows slight difference morphologically. Thewall porosity of established species and subspecies was analyzed by the electronic microscopy in the Institute of Biology and Biophysicsof Tomsk State University. The description of foraminifers was performed according to the instruction on the systematic description oforganisms developed in Palaeontology Institute of RAS in 1972. The habitat and geographical isolation factors play a significant role inthe systematics of Polymorphinidae. This naturally suggests that the geographical criterion must be taken into account. In studying thenew species and subspecies of the indicated family, the disagreement with Kuzina's data emerged not only in ages but also in thegeographical occurrence and location of the Polymorphinidae. By Kuzina, the Guttulina ipatovcevi Vassilenko Species occurs only inthe Dnepr-Donetsk Depression of Eastern Ukraine (the Romny District). The Siberian (geographical) Guttulina ipatovcevi Vassilenkosubsp. sibirica Kseneva Subspecies is common in the Campanian-Maastrichtian deposits of Western Siberia. All specimens of speciesdescribed in the present paper are deposited in the Micropalaeontological Department of the Palaeontology Museum of Tomsk StateUniversity. The studied taxa are illustrated on three plates. All natural specimens were painted from under the microscope byO.M. Lozovaya.

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