Late Cenozoic catfishes of Southeastern Europe with inference to their taxonomy and palaeogeography

Abstract

We describe fossil catfish (Siluriformes) material from late Miocene through Pleistocene strata of Southeastern Europe. The material under study is represented by disarticulated bones from 26 localities in the territory of Southern Ukraine and the Russian Federation. Catfish fossils in that region are represented by members of two genera, Heterobranchus and Silurus, of two families (Clariidae and Siluridae, respectively), and five species, including one as new for science (Silurus spinosus n. sp.) and two described in open nomenclature (Silurus cf. S. glanis, Silurus sp.). The presence of †Heterobranchus austriacus in the late Sarmatian of Southern Ukraine can be explained by expansion of this species from Africa to Europe during the late Miocene (earlier remains of this taxon were documented only in Central and Western Europe). Geographic distribution of Silurus soldatovi was broader in the past as indicated by the numerous findings of its bones in the late Miocene and Pliocene deposits of Southeastern Europe. Modern Silurus glanis first appeared during the final stage of late Miocene (Pontian) and probably supplanted S. soldatovi because of its wider ecological plasticity (especially temperature tolerance – this species can spawn in cooler waters). An interesting evolutionary trend has been observed in the change of size, shape and orientation of denticulations on the shaft of pectoral-fin spine in different species of the genus Silurus. Such tendency may be explained in terms of the oligomerization of homologous structures, but this question deserves a special study and is not addressed herein.