Palaeodysagrion cretacicus Zheng et al., 2016

Bechly, Günter & Velten, Jürgen, 2023, A Revised Diagnosis of Palaeodysagrion cretacicus Zheng et al., 2016 (Insecta: Odonata) from mid-Cretaceous Burmese Amber, with erection of a new genus of fossil damselflies, Zootaxa 5263 (4), pp. 547-556 : 549-551

Palaeodysagrion cretacicus Zheng et al., 2016

( Figures 1–9 )

Holotype. NIGP163546 (basal third of a hind wing). Since the holotype shows sufficient characters to distinguish it from P. youlini we see no necessity to apply to ICZN for designation of the new specimen as a neotype.

New specimen. Relatively complete specimen without number in the private collection of Hans Georg Müller (Gelsenkirchen, Germany). Since it is not a type specimen, we see no problem with this deposition in a private collection .

Locality and horizon. Burmese amber (Hukawng Valley, Kachin State, Myanmar). Mid-Cretaceous: earliest Cenomanian.

Diagnosis. Same as for genus, since monotypic after the removal of P. youlini to a new genus (see below).

Description of new material. The new specimen is preserved in a 31 gram amber piece of 67*50* 15 mm size with multiple syninclusions of other arthropods. The right pair of wings is completely preserved (forewing above, hind wing below in the photos), while the left pair of wings is broken at the base and missing. The wing tips are darker coloured from apex to the level of basal end of pterostigma ( Figure 9 ), which clearly represents an original colour pattern. The pterostigmata have no discernible microsculpture. The wing veins (including crossveins) are equipped with medium length spines.

Body ( Figure 2 ). Head transverse as in Zygoptera (left eye fragmentary); prothorax small and saddle-shaped; pterothorax skewed as in Zygoptera , interpleural suture seems complete; base of abdomen (segments I–III) without visible secondary genital apparatus, but rest of abdomen missing; all six legs complete and very long, long femoral and tibial spines, femora distinctly longer than tibiae (pro-, meso- and metafemora 2.9, 3.2 and 3.9 mm, pro-, meso- and metatibiae 2.9, 2.9 and 4.6 mm), forelegs with cleaning comb along tip of tibia, tarsi 3-segmented, the tarsal claws are not totally and clearly visible but may lack a hook.

Forewing ( Figures 4–6 ). Intact, hyaline, 25.0 mm long and 5.1 mm wide at widest point; only 2 primary antenodal crossveins ax1 and ax2 1.4 mm apart; ax2 aligned with arculus; distance between wing base and arculus or nodus 3.0 or 6.6 mm respectively; nodus at 26.4 % of wing length, of normal structure with oblique nodal and less oblique subnodal veinlets aligned; 17 postnodal and 16 postsubnodal crossveins, aligned except for the distal 3–4; pterostigma 3.5 cells and 1.8 mm long, 0.6 mm wide; pterostigmal brace oblique; 8 crossveins distal of pterostigma; basal cell free; arculus angled; discoidal cell 1.4 mm long and 0.3–0.6 mm wide, subrectangular, and free; subdiscoidal cell free; RP midfork (branching RP1+2 and RP3+4) 6.0 mm distal of wing base and 1.3 basal of subnodus; bridge space free; IR2 aligned with subnodus; branching of RP1 and RP2 6.3 mm distal of subnodus; IR1 long and zigzagged, originating 3 cells distal of RP fork; distally 2 rows of cells between RP1 and IR1 and between IR1 and RP2; distally 2–3 rows of cells between RP2 and IR2, and 2–4 rows between IR2 and RP3+4; no lestine oblique vein ‘O’ between RP2 and IR2; MA reaching to distal end of MA distally zigzagged and parallel to RP3+4 with a single row of cells between them; about 9 cells between MA and MP along hind margin; MP without curvature at origin at discoidal cell; CuA zigzagged and parallel to MP, with a single row of cells in the field between CuA and hind margin; anal crossing (CuP) 0.4 mm basal of arculus; petiole 2.2 mm long; no accessory intercalary veins.

Hind wing ( Figures 7–8 ). Intact, hyaline, 24.6 mm long and 4.7 mm wide at widest point; only 2 primary antenodal crossveins ax1 and ax2 1.5 mm apart; ax2 slightly distal of arculus; distance between wing base and arculus or nodus 3.0 or 6.7 mm respectively; distance between ax2 and nodus 5.1 mm (in holotype 5.8 mm); nodus at 27.2 % of wing length, of normal structure with oblique nodal and less oblique subnodal veinlets aligned; 15 postnodal and 14 postsubnodal crossveins, more or less aligned with each other; pterostigma 3 cells and 2.3 mm long, 0.6 mm wide; pterostigmal brace oblique; 11 crossveins distal of pterostigma; basal cell free; arculus angled and sectors of arculus ( RP and MA) widely separated at origin; discoidal cell 1.6 mm long and 0.26-0.48 mm wide, subrectangular, and free, much more elongate than in forewing; subdiscoidal cell free; RP midfork (branching RP1 +2 and RP3 +4) 5.9 mm distal of wing base and 1.3 basal of subnodus; bridge space free; IR2 aligned with subnodus; branching of RP1 and RP2 5.2 mm distal of subnodus; IR1 long and zigzagged, originating 3 cells distal of RP fork; distally 2 rows of cells between RP1 and IR1 and between IR1 and RP2 ; distally 2–3 rows of cells between RP2 and IR2, and 2-4 rows between IR2 and RP3 +4; no lestine oblique vein ‘O’ between RP2 and IR2; MA distally zigzagged and parallel to RP3 +4 with a single row of cells between them; 12 cells between MA and MP along hind margin; MP without curvature at origin at discoidal cell; CUA zigzagged and parallel to MP, with a single row of cells in the field between CuA and hind margin; anal crossing (CuP) 0.35 mm basal of arculus; petiole 2.3 mm long; no accessory intercalary veins .

Figures

FIGURE 1. Photograph of the complete new specimen of Palaeodysagrion cretacicus, specimen coll. Müller. Scale bar = 5 mm.

FIGURE 2. Composite photograph of the body of Palaeodysagrion cretacicus, specimen coll. Müller. Scale bar = 3 mm.

FIGURE 3. Compositephotograph of rightpair of wingsof Palaeodysagrion cretacicus, specimencoll.Müller.Scalebar = 3mm.

FIGURE 4. Composite photograph of right forewing of Palaeodysagrion cretacicus, specimen coll. Müller. Scale bar = 3 mm.

FIGURE 5. Drawing of right forewing of Palaeodysagrion cretacicus, specimen coll. Müller. Scale bar = 5 mm.

FIGURE 6. Composite photograph of right forewing base of Palaeodysagrion cretacicus, specimen coll. Müller. Scale bar = 3 mm.

FIGURE 7. Composite photograph of right hind wing of Palaeodysagrion cretacicus, specimen coll. Müller. Scale bar = 3 mm.

FIGURE 8. Drawing of right hind wing of Palaeodysagrion cretacicus, specimen coll. Müller, with labeled wing venation. Scale bar = 5 mm.

FIGURE 9. Composite photograph of wing tips with pterostigmata of Palaeodysagrion cretacicus, specimen coll. Müller. Scale bar = 3 mm.