The megatooth shark, †, which likely reached at least 15 m in total length, is an iconic extinct shark represented primarily by its gigantic teeth in the Neogene fossil record. As one of the largest marine carnivores to ever exist, understanding the biology, evolution, and extinction of † is important because it had a significant impact on the ecology and evolution of marine ecosystems that shaped the present-day oceans. Some attempts inferring the body form of † have been carried out, but they are all speculative due to the lack of any complete skeleton. Here we highlight the fact that the previous total body length estimated from vertebral diameters of the extant white shark for an † individual represented by an incomplete vertebral column is much shorter than the sum of anteroposterior lengths of those fossil vertebrae. This factual evidence indicates that † had an elongated body relative to the body of the modern white shark. Although its exact body form remains unknown, this proposition represents the most parsimonious empirical evidence, which is a significant step towards deciphering the body form of †.

Marine basins that existed in present-day Ukraine during the Eocene harboured various groups of cartilaginous and bony fishes, reptiles, aquatic birds, and marine mammals. Fish remains from Paleogene deposits of Kyiv and its vicinities were first collected and described by O.S. Rogovich in the mid-19th century. Here we have carried out a re-examination of chondrichthyan fossils from Rogovich's collection and evaluated several later records, all of which were recovered from middle Eocene deposits. In total, 88 specimens represented by teeth, vertebrae, and other skeletal elements were analysed and described. As a result, the sample revealed to a single chimaeriform species , and 12 shark and two ray taxa, respectively. Ten sharks were identified to species level, whereas the rays could be identified only at higher systematic ranks (Myliobatidae, Myliobatiformes). Several nomenclatural changes are proposed here, including the synonimisation of , and with more recently proposed taxa. Seven species erected by Rogovich , and ) are suggested to most likely be . Many identified taxa represent the epi- and mesopelagic fishes and only a relatively small number of them belong to benthopelagic, demersal, and bathydemersal forms. The studied sample is of important historical and scientific value and substantially contribute to the understanding of the palaeodiversity of Eocene marine ecosystems that existed in present-day Ukraine and generally in Eastern Europe.