Presented are the latest findings from investigating bottom sediments in Lake Arakhlei, containing continuous records of the vegetation evolution in the Beklemishevskaya depression and its mountain surroundings for the last 13 500 years.

Pleistocene water bodies have been studied using the paleolimnological approach, which traces environmental changes using particular subfossils as ecological proxies, rather than analysis of the paleocommunities themselves. Within a given taphocoenosis, the presence and quantity of animals are related to environmental conditions rather than to community types where relationships between taxa are stabilized during their long-term co-occurrence and are (at least partially) more important than the particular environmental conditions at the time of deposition, which may have experienced significant seasonal and inter-seasonal variations. Here, we analyze Branchiopoda (Crustacea) of two paleolocalities in the Transbaikalian Region of Russia: Urtuy (MIS3) and Nozhiy (older than 1.5 million years). Cladocerans Daphnia (Ctenodaphnia) magna, D. (C.) similis, D. (Daphnia) pulex, Ceriodaphnia pulchella-reticulata, C. laticaudata, Simocephalus sp., Moina cf. brachiata, M. macropopa clade, Chydorus cf. sphaericus, Capmtocercus sp. and anostracans Branchinecta cf. paludosa, and Streptocephalus (Streptocephalus) sp. are found in two localities. With the exception of the last taxon, which now occurs in the southern Holarctic, all other taxa inhabit the Transbaikalian Region. Within Eurasia, the steppe zone has the greatest diversity of large branchiopods and a high diversity of some cladocerans, such as subgenus Daphnia (Ctenodaphnia) and Moina sp. Here we demonstrated that the branchiopod community in shallow steppe water bodies has been unchanged since at least the Pleistocene, demonstrating long-term morphological and ecological stasis.

Diverse epidermal appendages including grouped filaments closely resembling primitive feathers in non-avian theropods, are associated with skeletal elements in the primitive ornithischian dinosaurKulindadromeus zabaikalicusfrom the Kulinda locality in south-eastern Siberia. This discovery suggests that “feather-like” structures did not evolve exclusively in theropod dinosaurs, but were instead potentially widespread in the whole dinosaur clade. The dating of the Kulinda locality is therefore particularly important for reconstructing the evolution of “feather-like” structures in dinosaurs within a chronostratigraphic framework. Here we present the first dating of the Kulinda locality, combining U-Pb analyses (LA-ICP-MS) on detrital zircons and monazites from sedimentary rocks of volcaniclastic origin and palynological observations. Concordia ages constrain the maximum age of the volcaniclastic deposits at 172.8 ± 1.6 Ma, corresponding to the Aalenian (Middle Jurassic). The palynological assemblage includes taxa that are correlated to Bathonian palynozones from western Siberia, and therefore constrains the minimum age of the deposits. The new U-Pb ages, together with the palynological data, provide evidence of a Bathonian age—between 168.3 ± 1.3 Ma and 166.1 ± 1.2 Ma—forKulindadromeus. This is older than the previous Late Jurassic to Early Cretaceous ages tentatively based on local stratigraphic correlations. A Bathonian age is highly consistent with the phylogenetic position ofKulindadromeusat the base of the neornithischian clade and suggests that cerapodan dinosaurs originated in Asia during the Middle Jurassic, from a common ancestor that closely looked likeKulindadromeus. Our results consequently show thatKulindadromeusis the oldest known dinosaur with “feather-like” structures discovered so far.

Chemical, radioisotopic, and palynological studies of the bottom sediments of mesotrophic Lake Arakhlei have been carried out for paleoclimatic reconstructions and estimation of the sedimentation rate.