May of 2026 marks the 150th anniversary of the outstanding biologist and geo­grapher, theorist and historian of science, Academician, Moscow University graduate Leo S. Berg (1876–1950), who became famous during his life as the greatest ichthyologist in our country. He published numerous papers with descriptions of single fish species, as well as general monographs on the ichthyofauna of our country and its regions. He also focused on fishing, domestic aquaculture and zoogeographical zoning by ichthyofauna. The article discusses L.S. Berg’s research on palaeontology, which began during his expeditions to the Aral Sea in 1899–1906. He studied the Meso-Cenozoic deposits of the Aral coastline and their fossil fauna. Since the 1930s, Leo Berg continued his palaeoichthyological research, studying in detail the Late Paleozoic, Mesozoic and Cenozoic actinopterygian and other fishes. He described a number of fossil taxa of ichthyofauna and critically revised the system of fossil agnathans and fishes. The article provides brief biographical information of L.S. Berg, one of the classics of world ichthyology in the 20th century.

May of 2025 marks the 180th anniversary of the Siberian researcher, geologist and geo­grapher Jan Stanislaw Franciszek Czerski (1845–1892). However, he worked not only in the field of geology and geography. An important part in Czerski’s researches was works on paleontology and zoology; he is also known as an archaeologist. In 1871–1879, Czerski worked at the museum of the Siberian (Eastern Siberian) Branch of the Imperial Russian Geographical Society in Irkutsk. He studied, catalogued and significantly expanded the zoological and paleontological collections of the museum. The article provides brief information from Jan Czerski’s life. His main works on the study of modern and quaternary Siberian mammals, which laid the foundation for further research in this area, are analyzed. Czerski’s paleontological research ranks him among the outstanding palaeontologists of the second half of the 19th century.

The position of the nasal sacs and nostrils, as well as some features of the brain structure in antiarchs (placoderm fishes) are analyzed, based mainly on the examples of Bothriolepis and Asterolepis. A new possible reconstruction of the olfactory system and brain in antiarchs is proposed. The paired nasal sacs are closely located to the anterior wall of the telencephalon; tracti olfactorii are absent; telencephalon is situated anterior to the diencephalon, as it was reconstructed for other placoderms; and the epiphysis process is elongated. The mesencephalon, cerebellum and medula oblongata, bearing the fossa romboidea, are placed posterior to the diencephalon in the otico-occipital part of the endocranium.

New data on the placoderm fish Plourdosteus livonicus (Eastman, 1896) from the Lower Frasnian deposits of the Mikhaylovsky Mine in the Kursk Region is described. These remains are currently housed at the Earth Science Museum of Lomonosov Moscow State University. The medio-dorsal plate from this locality allows reconstructing its form and proportion, as also early unknown anterior division of the bone. Only small fragments of medio-dorsal plates were formerly described and figured for P. livonicus from this and other localities in European Russia. So, the new data from the Mikhaylovsky Mine adds to the morphology information of this species. The medio-dorsals are of diagnostic significance and distinguish in the plourdosteids. The specimen from the Earth Science Museum’s collection is compared with the medio-dorsal plates of other Frasnian Plourdosteus species from the East-European platform.

The palaeoichthyological collection from the Bilovo locality in the Tver’ region (Famennian of the Main Devonian field), currently housed at the Andreapol Museum of Local History, is continued to be studied. Placoderm fishes of the family Bothriolepididae Cope predominate in the ichthyocomplex of this locality. Rare plates of large-bodied Bothriolepis sp. with a flattened armor were found at the Bilovo locality in clay deposits in addition to numerous remains of crested bothriolepidids. The material on Bothriolepis sp. is represented by three posterior medio-dorsal plates only. These plates are described, figured and compared with a similar material on Late Devonian bothriolepidids from the Main Devonian field and other regions. A brief characteristic of the Bilovo locality is given as well.