First Eugereonidae (Insecta: Palaeodictyoptera) from the Pennsylvanian (Late Carboniferous) of the Piesberg site near Osnabrück, Germany

Sandiella herbigi sp. nov. is the first record of the family Eugereonidae Handlirsch, 1906 (Insecta: Palaeodictyoptera) in the Pennsylvanian (Late Carboniferous: Westphalian D) sequence of the Piesberg quarry near Osnabrück, Lower Saxony, Germany. It is represented by a single fragment of a mesothoracic wing with the typical coarse reticulation in this family. The species is mainly characterized by the following features: (i) the shape of the mesothoracic wing is extremely narrow, (ii) the posterior subcostal vein is ending before the wing apex, (iii) all the main veins show a typical bend close to the posterior margin. The new wing is the second most ancient record of the Eugereonidae.

During the last 3 decades more than 1300 remains of insects and insect nymphs were collected, most of them preserved as isolated wings or wing fragments. The larger number of these fossils was collected by the amateur collector Michael Sowiak (Glandorf near Osnabrück) and one of the authors (A.L.). Only a smaller part has already been described, and the research is still continuing.
Due to the large number of new taxa and the high diversity, the Piesberg site is one of the most important localities for Pennsylvanian (Late Carboniferous) insects which in the meantime received international scientific interest.

Materials and methods
The analytical drawing of the specimen was prepared from photographs by one of the authors (A.L.) using the free painting program paint.net. The photograph was taken using a Canon EOS 350 D camera with Objective Canon Handling Editor: Sven Hartenfels. EFS 18-55 mm and EFS 60 mm, using a copy stand with daylight lamps. Diaphragm was 18 with different exposure times.
As already used in earlier papers on Palaeodictyoptera from the Piesberg site (for example, Brauckmann et al. 2016), the terminology of the wing venation follows Kukalová-Peck and Richardson (1983)

Geological setting
The specimen described was collected from layer 4 of freshwater lake sediments discovered in 2018 between the seams "Mittel" and "Johannisstein" and are thus of middle Westphalian D/Asturian (Pennsylvanian, Late Carboniferous: Moscovian) age. This new deposit has yielded several meso-and xerophyllous plants which are normally not preserved in Pennsylvanian coal-bearing strata and an accompanying fauna which differs from the other Piesberg fossil bearing strata in a shift of occurrences and some new taxa for this locality (Leipner 2019;Leipner and Chellouche 2019;Wrede et al. 2019). Further details concerning the geology and stratigraphy, as well as the fossil content, of the Pennsylvanian (Late Carboniferous) sequence in the Osnabrück region has been compiled by Köwing and Rabitz (2005), Brauckmann and Herd (2002), Dunlop et al. (2008), and Haug et al. (2013) which we refer to.

Genera and species included. Eugereon boeckingi
D. sepultus (Meunier, 1910) A further distal fragment of a wing from the Meisenheim Formation M4 (Autunian) of Sitters (Saar-Nahe Basin) was tentatively assigned to the Eugereonidae by Poschmann and Schindler (2004), but not yet described in detail.
Remarks. The Eugereonidae can easily be recognized by the strong differences in the shape of their mesothoracic (long and narrow) and metathoracic wings (distinctly shorter) as well as by the crossveins forming a dense and rather coarse reticulation. Only both the Sandiella species are of Westphalian age. All the other Eugereonidae are of younger Stephanian and Autunian age.
As shown by the preserved head and body structures of Eugereon boeckingi, the Eugereonidae share typical morphological characters with other Palaeodictyoptera, as for example, (i) a small head with a slender haustellate beak and inconspicuous leg-like maxillary palpi, (ii) a narrow prothorax with a pair of small prothoracic wings, and (iii) non-overlapping mesothoracic and metathoracic wings. The abdomen and the cerci are still not known, but due to the proportions of the thorax, we should expect a rather short abdomen, and similar to other Palaeodictyoptera, a pair of rather long and delicately setaceous cerci with a great number of segments. The haustellate beak indicates that the animals were feeding on spores or vegetable juices. With a wingspan between 12 and 32 cm, the Eugereonidae are mediumsized to larger representatives of the Palaeodictyoptera.
Diagnosis. Wing with an estimated total length of about 90 mm, and an estimated maximum width of 12 mm, with the following main characters: (i) mesothoracic wing extremely long and slender; (ii) ScP− ending in C+ (or dissolving) far before wing apex; (iii) all preserved main veins with a marked bend close to posterior margin; (iv) crossveins rather coarse, densely reticulated.
Description. Distal fragment of long and extremely slender mesothoracic wing, preserved from apex to MP2−; preserved length = 41 mm (estimated total length = 90 mm), maximum width = 10.5 mm; anterior margin almost straight, apex narrowly rounded, slightly shifted in posterior direction; posterior margin nearly straight, but very slightly undulated (bend inwards at MA+ and MP2−); as far as preserved, C+ , ScP− and RA+ sub-parallel, very close to each other; ScP− short, ending in C+ (or dissolving) far before apex (similar to Sandiella readi); RA+ simple, ending in C+ near to apex; inter-radial area (= area between RA+ and RP−) very narrow; RP− with 7 terminal branches, only the proximal branch bifurcate, distances between each branch of RP− far; separation of RA+ and RP− not preserved, evidently in proximal part of wing; MA+ simple, ending about 25 mm from wing apex into posterior margin (distinctly farther from apex than in S. readi); MP− with at least 2 branches; all preserved main veins with a marked bend close to posterior margin; crossveins rather coarse, forming a very dense archedictyon.
Comparison. The general characters of Sandiella herbigi sp. nov. (long and slender mesothoracic wing, rather simple main venation, cross veins rather coarse, forming a dense archedictyon) are typical for the Eugereonidae.
The new species shares with Sandiella readi (i) the short ScP− and (ii) the rather coarse archedictyon and is, therefore, here assigned to Sandiella. S. herbigi sp. nov. differs from the stratigraphically older S. readi mainly by its slightly larger dimensions and the still more slender shape. Further differences are (i) the narrower inter-radial area (= area between RA+ and RP−), (ii) the larger distances between each branch of RP− and (iii) the distinctly more proximal position of the ending of MA+ into the posterior margin in S. herbigi (Table 1).
The species of Dictyoptilus differ mainly by their distinctly longer ScP−, the apparently less coarse archedictyon and their larger dimensions.
Peromaptera filholi differs by the slightly broader shape, the markedly undulated posterior margin and the less dense archedictyon.
Beyond the small head with a slender haustellate beak, the prothorax with legs and small prothoracic wings, as well as remains of the mesothorax and metathorax, in Eugereon boeckingi only the basal parts of the wings are preserved. Therefore, a more detailed comparison is not possible. With an estimated length of the mesothoracic wing of about 75-80 mm, it is a little bit smaller than Sandiella herbigi.
Valdeania medeirosi shows the typical wing proportions of the Eugereonidae. As far as one can judge from the tectonic distortion, it seems to differ from Sandiella herbigi by the much more curved main veins and the less number of branches of RP.

Conclusions
The new species enlarges the regional and stratigraphical range of the palaeodictyopteran insect genus Sandiella and fills a gap within the record of the Eugereonidae.
Acknowledgements Dr Elke Gröning (Clausthal-Zellerfeld, Germany) helped to improve the manuscript. Dr Jarmila Kukalová-Peck (Ottawa, Canada) is thanked for her repeated help. We also thank the GP Papenburg company for their permission for palaeontological field work in their quarry and technical assistance, the creators of the free painting program paint.net, Dr Andrew J. Ross (Edinburgh) and an anonymous reviewer for their helpful comments, and in particular Dr Mike Reich and Professor Dr Michael Amler for editorial support. Without the enormous field work of Michael Sowiak, the discovery of the described insect wing would not have been possible to achieve in time. Funding Open Access funding enabled and organized by Projekt DEAL.
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