Order Palaeodictyoptera Goldenberg, 1877 (= Dictyoneurida sensu Sinitshenkova 2002)
Remarks. The higher classification of this order is still discussed controversially.
Family Eugereonidae Handlirsch, 1906
Diagnosis. Carpenter (1992: 31).
Further details. Carpenter (1964, 1970); Kukalová (1969).
Genera and species included. Eugereon boeckingi Dohrn, 1866 (type species), Cisuralian (Lower Permian: Autunian), Schwarzenbach near Birkenfeld, Saar-Nahe Basin, Germany (further details: Brauckmann 2007: 177);
Dictyoptilus renaulti Brongniart, 1893 (type species), Pennsylvanian (Late Carboniferous: Stephanian), Commentry, France;
D. peromapteroides (Meunier, 1908), Pennsylvanian (Late Carboniferous: Stephanian), Commentry, France;
D. sepultus (Meunier, 1910), Pennsylvanian (Late Carboniferous: Stephanian), Commentry, France;
Peromaptera filholi Brongniart, 1893 (type species), Pennsylvanian (Late Carboniferous: Stephanian), Commentry, France;
Sandiella readi Carpenter, 1970 (type species), Pennsylvanian (Late Carboniferous; Sandia Formation), Sandia Mountains, eastern suburbs of the city of Santa Fe, New Mexico, USA (the terrestrially influenced higher sequence of the Sandia Formation can approximately be allocated to the Westphalian C = Bolsovian, Moscovian (Schneider et al. 2019); thus Sandiella readi is clearly the most ancient member of the Eugereonidae);
S. herbigi sp. nov., Pennsylvanian (Late Carboniferous: Westphalian D/Asturian), Piesberg near Osnabrück, Germany;
Valdeania medeirosi Teixeira, 1941 (type species), Pennsylvanian (Late Carboniferous: Stephanian), Valdeão near Valongo E Porto, Portugal.
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 wing-span between 12 and 32 cm, the Eugereonidae are medium-sized to larger representatives of the Palaeodictyoptera.
Genus Sandiella Carpenter, 1970
Type species. Sandiella readi Carpenter, 1970, Pennsylvanian (Late Carboniferous: Westphalian B, late Bashkirian to early Moscovian), Sandia Mountains, New Mexico, USA.
Diagnosis. Carpenter (1970: 405; 1992: 31, modified). Similar to Dictyoptilus but with a coarser reticulation of crossveins and without rows of crossveins between RA and RP; Sc ending well before apex of wing.
Species included. Sandiella readi Carpenter, 1970 (Fig. 1) and S. herbigi sp. nov. (Fig. 2).
Sandiella herbigi sp. nov.
Holotype. Wing no. Pal 1670, distal fragment of right wing, collected by one of the authors (AL), deposited in the Museum am Schölerberg, Osnabrück.
Type locality and type stratum. Pennsylvanian (Late Carboniferous): middle Westphalian D/Asturian: lake deposit between seam “Mittel” and seam “Johannisstein”, Piesberg near Osnabrück, Germany.
Etymology. In honour of Professor Dr. Hans-Georg Herbig, Cologne.
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.