The first record of Scheenstia (Actinopterygii, Holostei) from the Late Cretaceous of Ukraine in the context of European occurrence of Mesozoic lepisosteiform fishes

Abstract

Lepisosteiform fishes are represented in the fossil record of Europe from the Late Jurassic until the Miocene. Most of their remains were found in the western and central parts of the continent. Here we report about a new find of the large and exceptionally well-preserved ganoid scale sharing similar morphological features with those in Scheenstia. It comes from the Upper Cretaceous (middle Cenomanian) marine deposits of Nova Ushytsia locality (western Ukraine). The age of these deposits is estimated as ca. 98–95 Ma due to the presence of ammonites Turrilites costatus, T. acutus, Acanthoceras cf. rhotomagense, and Schloenbachia coupei. The faunal assemblage also includes sharks, gars, reptiles, sponges, corals, bivalves, gastropods, bel-emnites, brachiopods, and bryozoans. The specimen described here is characterized by the presence of the longitudinal “peg-and-socket” articulation formed by two almost equally well-developed anterior processes and smooth surface lacking the regular structure inherent to lepisosteids. Lithological and paleontological investigation of Nova Ushytsia suggests the presence of an epicontinental, shallow and ramified sea with normal salinity and well-aerated warm water (+17–20 °C), temporary strong bottom currents and deep-wa-ter areas up to 150–200 m (10–80 m in average) with soft muddy bottom. Almost complete phosphatization of the early-middle Cenomanian faunal remains indicates an important role of the Carpathian upwelling. Microscopic observation of the studied scale surface and the presence of etched areas and digestion marks suggests that this fish specimen probably was a prey of ichthyosaur Platypterygius indicus Lydekker, 1879, which remains were also found in this locality. Scheenstia was a nektonic carnivore inhabiting marine coast-al areas with normal salinity. The finding of Scheenstia in Ukraine is recently the youngest known record of this genus within the former European Archipelago extending its temporal range up to the Late Cretaceous. It allows filling the gap in lepisosteiform occurrences within Eurasia during the Mesozoic.

Keywords

• lepisosteiformes
• scale
• morphology
• biogeography
• cenomanian
• eastern europe