Insect fossil gems from iron concretions
Concretions are solid, usually spherical, accumulations of specific rocks and minerals that form around a solid core in sediments. They are often found in both unconsolidated and consolidated rocks of various ages.
The research team described newly found insect specimens based on wings from the Carboniferous period. The samples come from Sosnowiec (Poland) and Mazon Creek (USA), and both demonstrate remarkable preservation of original venation. Newly designated taxa belong to the polyneopteran clade and are closely related to Dictyoptera, a group comprising cockroaches, termites, and mantids.
The specificity of these fossil insects lies primarily in the unique pattern of wing venation. For classification into the proper taxon, these alar characters are in many cases all that is available.
In their paper, the researchers described a new genus and species of dictyopteran fossil insect, Sosnowiecia dareki. The generic name originates from the name of the town of Sosnowiec in Silesia, Poland, where the fossil was found. The name of the species honours the collector who found the fossil wing at the locality. The second output of the scientific article is the description of a new species of Stephanopsis testai from Mazon Creek in the USA, also named after a renowned researcher from this locality, Thomas V. Testa. These blattoid-like insects dominated in multiple localities in the Late Carboniferous.
The described specimens were deposited in the Field Museum of Natural History (Chicago, USA) and the Natural History Museum of the Institute of Systematics and Evolution of Animals PAS (Krakow, Poland), respectively.
The world-famous Mazon Creek locality is well known in the literature, not only in terms of fossil insects. This is primarily due to the excellent conservation of fossils (the site is also referred to as Lagerstätte, a site with exceptional preservation). By contrast, Sosnowiec remains outside of interest in the scientific literature. Nevertheless, the preservation of fossils at this site is comparable. In both localities, fossils are preserved in typical iron concretions with high fidelity in terms of structural detail.
With regard to stratigraphy, the Mazon Creek concretions belong to the Carbondale Formation (Moscovian stage). The finds from Sosnowiec in Lower Silesia come from the Mudstone series ‒Załęże beds (Langsettian sub-stage).
Unlike Carboniferous insect fossils from the territory of the Czech Republic, fossils in concretions are preserved in 3D. This difference in preservation within the Upper Silesian Basin offers an exciting aid for a more detailed description of the fossils. The added value of similar papers lies in newly acquired foreign collaborations, as a result of which Czech scientific research is now more visible worldwide.
Tomáš Dvořák, Wiesław Krzemiński & Jakub Prokop (2022): New stemdictyopteran insects from the Pennsylvanian deposits at Mazon Creek and Sosnowiec (Insecta: Polyneoptera), Historical Biology, DOI: 10.1080/08912963.2022.2140423