A perciform fish from the Oligocene of Krosno area
A fossil fish from the order Perciformes was found in the Outer Carpathians, in marginal part of the Silesian Unit, in rocks dated to the Oligocene (34-23 million years). At this locality, there is an exposure of beige and brown siliceous shales intercalated with grey thin-bedded (4-5cm) sandstones and beige cherts. There are also beige diatomaceous shales (rocks with diatoms). The rocks at the locality represent the upper part of the Menilite Formation (Rudawka Tractionite Member). They are rich in organic matter - mostly from unicellular algae.
The order Perciformes is considered to be the youngest group of fishes and the most numerous in species in the class Actinopterygii. The order contains more than 150 families, which are grouped in 19 subfamilies. Diagnostic features of the studied fish are: nine spines in dorsal fin, three spines in anal fin, preopercle with spines, lachrymal serrated, vertebral column including 23 vertebrae.
The author interprets the fossil as a juvenile specimen, a close relative of Capros (Caproidae) orfamily Leiognathidae. Some morphologic features indicate similarity to Caprosimilis(representative of superorder Acanthopterygii). All taxa shares body proportions, deep body, nine spines in dorsal fin, three spines in anal fin, lachrymal serrated. Caprosimilis differs in number of vertebrae 24 (versus 23), but one vertebra could be invisible because were covered by posterior bones of the head. Caprosimilis andCapros have preopercle distinctly serrated in juveniles and adults. Leiognathidae have indistinct serration in adults while in juveniles it is not known.
Capros, Caprosimilis and Leiognathidae are very rare in the Polish Outer Carpathians. Capros is known Rudawka Tractionite Member and younger deposits of the Menilite Formation (up to Błażowa Member). Caprosimilis is known by single specimen from Rudawka Tractionite Member. Leiognathidae are known by single specimen from deposits coeval to studied here Rudawka Tractionite Member. They are noted also from much younger Jasło Limestones and the Krosno Formation. They are represented by Equula? sp. and Leiognathus cf. minutus.
Further detailed anatomical study, especially of head, of the described here fossil fish is necessary to determine more precisely its taxonomy. This fossil is an interesting, unusual find, it is potential source our knowledge about anatomy of Actinopterygii from the Polish Outer Carpathians.
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Bieńkowska-Wasiluk, M., & Bonde, N. (2015). A new Oligocene relative of the Caproidae (Teleostei: Acanthopterygii) from the Outer Carpathians, Poland. Bulletin of Geosciences, 90, 461–478.
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Kotlarczyk.J et al. 2006. A framework of ichthyofaunalecostratigraphy of the Oligocene-early Miocene strata of the Polish Outer Carpathian basin. AnnalesSocietatisGeologorumPoloniae 76(1), 1–111.
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