No 2 (2024)

There are important morphological differences between the dominant higher taxa (classes) in associations of radiolarians that lived at different depths of paleobasins. A similar inversion of dominant radiolarian taxa can be seen in the Early Tournaisian (Mississippian) and the Kungurian (Cisuralian) and may indicate a change in their habitat from deeper conditions where porous Sphaerellaria dominant, to less deep-water shelf environments, in which spongy-lattice Spumellaria prevailed.

Based on the re-examination of the previously established species Aviculopecten volucer Lutkevich et Lobanova of the Late Permian (Late Wuchiapingian-Early Changhsingian) pectinids, which was considered a synonym of the Middle Permian Vnigripecten phosphaticus (Girty), the independence of both species is shown. Features of the peculiar shell morphology and sculpture of Aviculopecten volucer make it possible to describe the new genus Voluceropecten gen. nov. and the monospecific family Voluceropectinidae fam. nov. A corrected diagnosis of the genus Vnigripecten Muromzeva is given.

The shell microstructure of rarely discovered lingulate genus Praeoehlertella Mergl, 2001 was studied in detail. It was obtained in Famennian stage of Kazakhstan. The peculiarity of the microstructure the secondary granular layer was discovered. The prints of the cells of the inner epithelium of mantle were observed.

Described two new species of cornutan stylophora of the genus Phyllocystis from the Volkhov Regional Stage (Middle Ordovician, Dapingian) of Baltica. This points to the biogeographic connection between Afro-European part of Gondwana and Baltica since the very beginning of the Middle Ordovician. Both species were confined to cold-water, shallow conditions with low water mobility. Analysis of the axial symmetry of the stylophora and the location of the hydropore indicates the absence of torsion in their ontogeny and the location of the ambulacral system to the right of their anteroposterior axis. To explain this structure, two alternative hypotheses have been proposed: 1) inversion inversion in the development of right and left coelomes; 2) inverted state of stylophora compared to other invertebrates, what makes them similar to the chordates in terms of the position of the dorsal and ventral sides.

From the Sundyr-1 reference locality of the Sundyr faunal assemblage of Eastern Europe (Upper Permian, Upper Severodvinian Substage, Suchonica vladimiri Assemblage Zone), the oldest species of the genus Dvinosaurus Amalitzky, 1921 Dvinosaurus gubini sp. nov. The diagnostic criterions for the new species are its smaller size compared to other dvinosaurs, the narrowest skull, short and wide zygomatic bone, parasphenoid body with a more wide base of the cultriform process and a well ossified basisphenoid, a strongly curved dentary with a well-defined symphyseal crest extending downward from the labial side of the symphysis and, in a several cases, with a single symphyseal canine, a large angle (135–152°) between the clavicular plate and the dorsal process of the clavicle, narrow areas of the interclavicle for insertion of the clavicles, narrow entepicondylus of the humerus. The size, narrowness of the skull, the presence of a single symphyseal canine, and hypocentrum structure bring together a new form closer to the basal Dvinosauria, in particular, with ancestral Trimerorhachidae.

The paper describes fossil remains of Promephitis lartetii (Mephitidae) from the Upper Miocene (MN 12-13) of Tuva, the Taralyk-Cher locality, presented by two nearly complete deformed skulls, mandibular rami, and maxilla, mandible fragments, and isolated teeth. The variability of taxonomically significant characters in the morphology P4-M1 and the skull of P. lartetii has been studied. The stability of the taxonomic characters of the genus Promephitis has been analyzed.