New, large actinopterygian fishes from the upper Carboniferous of Nýřany, Czech Republic

Abstract

The lacustrine coal deposits at Nýřany, Czech Republic, yielded a diversified vertebrate assemblage of the Middle Pennsylvanian (Moscovian) age, represented by the remains of early tetrapods, as well as numerous freshwater ichthyofauna, including xenacanthiform sharks, acanthodians, dipnoans, and ray-finned fishes. However, unlike some other upper Carboniferous localities, the actinopterygian diversity is limited to the three small-bodied species, most of them endemic to Nýřany locality and the equivalent strata elsewhere, indicating that the true taxonomic diversity of the group at the locality may be biased. Here we describe first skeletal remains of large actinopterygian fishes from the site, including a new genus and species, Stambergichthys macrodens gen. et sp. nov., which is represented by a well-preserved mandible with teeth. The micro-computed tomographic techniques revealed in the specimen a presence of a complex neurovascular system innerving the teeth and the jaw, and supplying both with blood vessels. The dentition consists of a single row of massive, homodont, conical teeth, which possess simplexodont plicidentine on their base, the characteristics supporting the predatory ecology of the new species. The isolated skeletal remains of large-bodied actinopterygians expand the knowledge on the diversity of the group in Nýřany, and their occurrence in coal deposits of relatively shallow lake indicates they represent allochthonous, poorly known aquatic vertebrate association, likely originating from the braided river system. These findings underline the importance of less complete skeletal materials occurring in wellknown vertebrate assemblages of the upper Carboniferous coal-bearing localities.

Keywords

• actinopterygii
• dentition
• continental basins
• morphology
• neurovascular system
• palaeoenvironment
• plicidentine
• palaeozoic