The decapod fauna from the Badenian (middle Miocene) deposits of western Ukraine comprises in total 31 taxa: 20 species, 9 taxa left in open nomenclature, and 2 determined at family level. Thirteen of these taxa are reported for the first time from the territory of Ukraine. Among them are the first records of Trapezia glaessneri Müller, 1976 in the Fore-Carpathian Basin and Pachycheles sp. in Paratethys. One taxon (Petrolisthes sp. A) probably represents a new species. The occurrence of this significant decapod fauna is restricted almost exclusively to the Upper Badenian (i.e., early Serravallian) coralgal reefs of the Ternopil Beds. The taxonomic composition of the decapods indicates that the Late Badenian depositional environment was a shallow marine basin dominated by reefs that developed in warm-to-tropical waters of oceanic salinity. The decapod assemblage from the Ternopil Beds is similar in its taxonomic composition to numerous decapod faunules from fossil reefs of Eocene to Miocene age from the Mediterranean realm and of Miocene age from Paratethys. In contrast, decapod remains are very scarce in Badenian siliciclastic deposits (Mikolaiv Beds) and are represented by the most resistant skeletal elements, i.e., dactyli and fixed fingers. This scarcity was caused by the high-energy environment, with frequent episodes of redeposition, which disintegrated and abraded the decapod remains.

Abstract Echinoderms from the Badenian (Middle Miocene) of the Fore-Carpathian Basin of western Ukraine are facies restricted. The Mykolaiv Beds, stratigraphically older, yielded the starfish Astropecten forbesi (complete skeletons), two genera of sand dollars (Parascutella, Parmulechinus), and numerous other echinoids of the genera Psammechinus , Echinocyamus, Spatangus, Hemipatagus, Echinocardium, Clypeaster, Echinolampas, and Conolampas. The stratigraphically younger, calcareous Ternopil Beds yielded Eucidaris (complete coronae, isolated spines), Arbacina , Brissus, and Rhabdobrissus. Sixteen species of echinoids are distinguished and/or commented. A new brissid, Rhabdobrissus tarnopolensis sp. nov., is established. A mass occurrence of some species (Psammechinus dubius and Hemipatagus ocellatus) contrasts with that of mass aggregations (sand dollars and Echinocardium leopolitanum) by dynamic events in selected layers of proximal tempestites. Of special note is the occurrence of very small specimens, interpreted as juveniles (‘babies’) having been swept out of their restricted biotopes (‘nurseries’). Some species hitherto regarded as of Early Miocene age, and the problem of their persistence beyond the Fore-Carpathian Basin and/or migration into that basin during the Middle Miocene transgression are discussed.