ELASMOBRANCH (CHONDRICHTHYES: ELASMOBRANCHII) FAUNAL COMPLEX FROM LATE ALBIAN (EARLY CRETACEOUS) OF KANEV DISLOCATIONS, UKRAINE

During Albian stage of Early Cretaceous cartilaginous fish experienced a rapid diversification event that lead to the exploitation of ecological niches previously unoccupied by them. There are few locations in the world where marine vertebrate complexes of this age can be studied. Sampling from six thin layers of quartz-glauconite sands in Kanev dislocations, Ukraine yielded more than three thousand vertebrate specimens, including elasmobranch teeth, chimaera dental plates, fish and sauropsid teeth and bones. Our study represents the first illustrated and detailed description of elasmobranch teeth from Ukrainian Albian deposits since Rogovich, 1860 monograph. Rogovich described several new species from this location and we got a chance to include in this work some of his specimens currently housed in the National Natural History Museum of National Academy of Sciences of Ukraine. This lead to resurrection of some of his species names, notably Polyacrodus bidentatus, Synechodus kessleri, Heterodontus minutus, Paraisurus monstrosus and Archaeolamna striata. In addition, our research provides insight into the systematics of Albian species of Synechodus and Heterodontus, specifically S. nitidus and S. tenuis validity and H. upnikensis dental morphology.

Studied complex, consisting of both our and Rogovich specimens, includes a typical benthic species group of synechodontiform, bullhead, angel, carpet and dogfish sharks. Strangely, batoid and hybodont finds are very rare, Meristodonoides teeth are present only in one layer of sands while lamniform sharks are the most common shark taxon. Lamniformes in Kanev Albian displays the highest ecological diversity, with small sand tiger shark species, early pseudoscapanorhynchids and large carnivorous sharks Cretoxyrhina and Cretolamna. Most importantly, Paraisurus and Cretoxyrhina vraconensis findings confirm Late Albian age of these deposits since they are usually described in geological literature non-specifically as Albian-Cenomanian.