Oligaeschna cf. jungi Piton and Théobald, 1939

Nel, André, Poschmann, Markus J. & Wedmann, Sonja, 2020, New dragonflies and damselflies (Odonata) from the late Oligocene of Enspel (Rhineland-Palatinate, SW Germany), Palaeontologia Electronica (a 59) 23 (3), pp. 1-24 : 2-8

Oligaeschna cf. jungi Piton and Théobald, 1939

Figures 1–4

Material. PE 2005/5032- LS a, b (part and counterpart of two forewings attached to fragments of thorax), specimen PE 2000 /5005- LS a, b (part and counterpart of a nearly complete forewing), specimen Enspel PE 1995/7217- LS (a complete forewing), specimen PE 1995/9174- LS (basal two-third

PALAEO- ELECTRONICA.ORG of a hind wing), all stored at the State Collection of Natural History of Rhineland-Palatinate .

Description. PE 2005/5032-LS a ( Figures 1.1–3, 3.1–2 ): Forewing, hyaline, 50.0 mm long, 11.3 mm wide; distance from base to arculus 5.2 mm; from arculus to nodus 19.3 mm; from nodus to pterostigma 15.3 mm, from nodus to wing apex 25.2 mm; pterostigma 4.3 mm long, 0.8 mm wide, covering five cells; pterostigmal brace elongate, distinctly oblique and sigmoidal; 16 secondary antenodal crossveins distal of Ax2 and four between Ax2 and Ax1; Ax2 at level of mid part of discoidal triangle; Ax1 well basal to arculus; arculus strongly angled; 14 antesubnodal crossveins; at most 14 postnodal crossveins and 17 postsubnodals; hypertriangle elongate, with four crossveins; discoidal triangle elongate, divided into five cells; three rows of cells in basal part of postdiscoidal area; median space free; submedian space with five crossveins plus CuP stronger than other crossveins; Mspl strongly curved, four rows of cells between Mspl and MA; four Bq crossveins; oblique vein ‘O’ one cell distal of base of RP2; MA with a smooth curve opposite base of Rspl; beyond this

NEL, POSCHMANN, & WEDMANN: ODONATA FROM ENSPEL level, two rows of cells between MA and RP3/4; Rspl strongly curved, with four rows of cells between it and IR2; IR2 unforked, with a posterior curve; four rows of cells between IR2 and RP 2 in broadest part; RP2 distinctly but smoothly curved at level of pterostigma.

Specimen PE 2000 /5005-LS a ( Figures 2.1 , 3.3 ): Forewing, hyaline, 45.1 mm long, 10.3 mm wide; distance from base to arculus 7.2 mm; from arculus to nodus 14.0 mm; from nodus to pterostigma 14.8 mm, from nodus to wing apex 22.7 mm; pterostigma 3.9 mm long, 0.8 mm wide, covering four cells; pterostigmal brace elongate, distinctly oblique and sigmoidal; exact number of secondary antenodal crossveins unknown Ax2 at level of mid part of discoidal triangle; Ax1 well basal to arculus; arculus strongly angled; 12–13 antesubnodal crossveins; 13 postnodal crossveins and 12 postsubnodals; hypertriangle elongate; discoidal triangle elongate, divided into five cells; three rows of cells in basal part of postdiscoidal area; median space free; Mspl strongly curved, four rows of cells between Mspl and MA; three Bq crossveins; oblique vein ‘O’ one cell distal of base of RP2; MA with a smooth curve opposite base of Rspl; beyond this level, two rows of cells between MA and RP3/ 4; Rspl strongly curved, with four rows of cells between it and IR2; IR2 unforked and with a posterior curve; four rows of cells between IR2 and RP 2 in broadest part; RP2 distinctly but smoothly curved at level of pterostigma.

Specimen PE 1995/7217-LS ( Figures 2.2 , 3.4 ): Forewing, hyaline, 48.8 mm long, 11.5 mm wide; distance from base to arculus 5.5 mm; from arculus to nodus 18.9 mm; from nodus to pterostigma 14.9 mm, from nodus to wing apex 24.2 mm; pterostigma 4.2 mm long, 0.8 mm wide, covering three cells; pterostigmal brace elongate, distinctly oblique and sigmoidal; 14 secondary antenodal crossveins distal of Ax2 and four between Ax2 and Ax1; Ax2 at level of mid part of discoidal triangle; Ax1 well basal to arculus; arculus strongly angled; 14 antesubnodal crossveins; 12 postnodal crossveins and 16 postsubnodals; hypertriangle elongate, with four crossveins; discoidal triangle elongate, divided into five cells; three rows of cells in basal part of postdiscoidal area; median space free; submedian space with three crossveins plus CuP stronger than other crossveins; Mspl strongly curved, four rows of cells between Mspl and MA; three Bq crossveins; oblique vein ‘O’ one cell distal of base of RP2; MA with a smooth curve opposite base of Rspl; beyond this level, two rows of cells between MA and RP3/4; Rspl strongly curved, with four rows of cells between it and IR2; IR2 unforked but with a rudiment of asymetrical anterior branch, and with a posterior curve; four rows of cells between IR2 and RP 2 in broadest part; RP2 distinctly but smoothly curved at level of pterostigma.

Specimen PE 1995/9174-LS ( Figures 2.3 , 4 ). Basal two-third of a hind wing; hyaline; preserved part 42.2 mm long, 16.7 mm wide; distance between base and arculus 6.4 mm, between arculus and nodus 15.3 mm; two primary antenodal crossveins Ax1 and Ax2 visible, with no secondary crossvein basal of Ax1, five between Ax1 and Ax2, between C and ScP; nine antenodal crossveins distal of Ax2, distance between base and Ax1 5.0 mm, between Ax1 and Ax2 6.4 mm; median space free; four crossveins in submedian area; arculus between Ax1 and Ax2, slightly closer to Ax1; RP and MA nearly meeting at their base in arculus; posterior part of arculus not aligned with anterior part; hypertriangle crossed by four veins; discoidal triangle elongate, divided into five cells; 4–5 rows of cells in basal part of postdiscoidal area; convex trigonal planate tspl in postdiscoidal area rather well-defined but short and zigzagged; Mspl long, with a strong concave bend, and with four rows of cells between it and MA; MA and RP3/4 not parallel in their distal part, and MA with a concave bend before wing margin, two rows of cells between MA and RP3/4; base of RP2 aligned with subnodus; oblique vein ‘O’ one cell distal of base of RP2; RP2 more or less parallel with IR2; Rspl distinctly curved, with four rows of cells between it and IR2; anal angle strongly angular (male); membranule broad and darkened; anal loop closed, well-defined, broad and large, 3.0 mm long and 5.5 mm wide, divided into nine cells; two rows of cells between MP and CuAa between their base and nodus level; CuA with posterior branches that define groups of cells, and six rows of cells between it and posterior wing margin.

Remarks. These fossils have all the synapomorphies of the family Aeshnidae as defined by Bechly (1996), i.e., ‘aeshnid bulla’ in distal part of MA; Rspl distinctly curved with more than one row of cells between it and IR2, and area in between divided by oblique intercalary veins; three rows of cells in basal part of postdiscoidal area between level of distal angle of discoidal triangle and level of midfork; hypertriangle traversed by at least three crossveins. Following the study of von Ellenrieder (2002), these fossils would fall near the extant Oplonaeschna de Selys-Longchamps, 1883 , from the shape of the veins Rspl, IR2, and RP2. The closest modern genera differ either in the narrower area between Rspl and IR2 with less than three rows of cells, or in the forked IR2 (see Martin, 1908-1909, 1911). The fossils differ from the extant genus Oplonaeschna in the longer pterostigma covering three cells or more and in the presence of three rows of cells in basal part of postdiscoidal areas instead of two. The general pattern of venation fits quite well with the Cenozoic genus Oligaeschna Piton and Théobald, 1939 (revised in Nel et al., 1994). The Oligocene genus Kvacekia Prokop and Nel, 2002 , is also closely related to Oligaeschna and Oplonaeschna , but it is characterized by a pterostigma covering 5–6 cells (five in our fossils), and by five rows of cells in the area between IR2 and RP2 (four in our fossil and 3–4 in Oligaeschna ) (Prokop and Nel, 2002).

Apart from weak differences in wing sizes and proportions, these wings are very similar and can be attributed to the same species, even if there is some uncertainty in the presence vs. absence of a fork of IR2 for the hind wing specimen PE 1995/ 9174-LS. Its preserved part of venation fits quite well with that of the hind wing of the type series of Oligaeschna jungi and with the complete hind wing from Céreste attributed to this species by Nel et al. (2005c). Thus, we propose to attribute these fossils to Oligaeschna , in accordance with Wedmann (2000: fig. 5) and Wedmann et al. (2010: fig. 6d) who indicated that it is ‘probably Oligaeschna jungi ’.

The genus Oligaeschna comprises nine described species from Oligocene and Miocene deposits in North American and Eurasia. Oligaeschna bulgariensis has much more postnodals (21). Oligaeschna cf. jungi shares with O. palaeocoerulea the presence of four rows of cells between IR2 and RP2, five cells below the pterostigma, 14 postnodal crossveins and 17 postsubnodals, close distances between nodus and pterostigma (25.2 mm in Oligaeschna cf. jungi and 28.3 mm in the type of O. palaeocoerulea ). But O. palaeocoerulea has 10 rows of cells between IR2 and RP2 along wing margin, instead of five in Oligaeschna cf. jungi . Oligaeschna kvaceki is based on a hind wing of same length as our fossil and a pterostigma covering five cells, five rows of cells between IR2 and RP2 along wing margin, as in Oligaeschna cf. jungi . But it has 17 postnodals instead of 12–14 in Oligaeschna cf. jungi and a shorter pterostigmal brace (Prokop et al., 2007). Oligaeschna lapidaria has a pterostigma covering three cells and a shorter pterostigmal brace (Cockerell, 1913). Oligaeschna saurai also has a pterostigma covering three cells, a shorter pterostigmal brace, and five rows of cells between Rspl and IR2 (Peñalver et al., 1996). Oligaeschna wedmanni has a forewing of the same size as Oligaeschna cf. jungi , but five rows of cells between IR2 and RP2, and only three rows of cells between Mspl and MAa, unlike Oligaeschna cf. jungi (Nel and Fleck, 2014) . Oligaeschna ashutasica , based on a hind wing, has three rows of cells between RP2 and IR2, and three rows of cells between MAa and Mspl (Martynov, 1929). Oligaeschna separata has a forewing 44 mm long and 13 postnodals (Scudder, 1890).

Oligaeschna cf. jungi differs from the type series of Oligaeschna jungi in the presence of four rows of cells between IR2 and RP2 instead of five, pterostigma covering 3–5 cells instead of three, and wing lengths 45–50 mm instead of ca. 55–56 mm in O. jungi . These differences would hardly support a species separation between the two populations from France and Germany.

These fossil wings are of interest to show the intraspecific variability, which is rather important in the genus Oligaeschna . Nevertheless, the character ‘presence of three rows of cells in basal part of the forewing postdiscoidal area’ and ‘presence of 4–5 rows of cells in basal part of the hind wing postdiscoidal area’ appear stable enough to justify the separation between the two genera Oligaeschna and Oplonaeschna .

Figures

FIGURE 1. Oligaeschna cf. jungi, specimen PE 2005/5032-LS a. 1, Overall view of fossil with two forewings, remains of the thorax, and one leg; 2, Left forewing enlarged; 3, Right forewing enlarged. Scale bars are 10 mm.

FIGURE 2. Oligaeschna cf. jungi. 1, PE 2000/5000-LS a, forewing; 2, PE 1995/7217-LS, forewing; 3, PE 1995/9174- LS, hindwing. Scale bars are 10 mm.

FIGURE 3. Oligaeschna cf. jungi, interpretative drawings of wings. 1, PE 2005/5032-LS a, left forewing; 2, PE 2005/ 5032-LS a, right forewing; 3, PE 2000/5000-LS a, forewing; 4, PE 1995/7217-LS, forewing. Scale bars are 10 mm.

FIGURE 4. Oligaeschna cf. jungi, interpretative drawing of hind wing PE 1995/9174-LS. Scale bar is 10 mm.