Primorilestes magnificus, Nel, Simov, Bozukov & Marinov, 2016

Nel, A, Simov, N, Bozukov, V & Marinov, M, 2016, New dragonflies and damselflies from Middle Miocene deposits in SW Bulgaria (Insecta: Odonata), Palaeontologia Electronica 25 (2), pp. 1-13 : 8-10

Primorilestes magnificus sp. nov.

Figure 4

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Etymology. Named after the fine state of preservation of the type specimen.

Material. Holotype Сат-52, Nr. Сат-53 (part and counterpart, Figure 4.1-2 ), paratype Сат-54 ( Figure 4.3 ). Division of Palaeobotany and Palynology , Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Sofia, Bulgaria.

Diagnosis. Wing venation only. Base of RP2 10 cells distal of subnodus; area between MP and posterior wing margin very broad and long; area between CuA and posterior wing margin broad with six secondary longitudinal veins; area between MA and RP3/4 very broad.

Description. Holotype Сат-52, Nr. Сат-53 ( Figure 4.1-2 ). Preserved part of wing on part 26.0 mm long, wing ca. 32.0 mm long, 7.1 mm wide; distance from wing base to arculus 4.8 mm, arculus to nodus 4.4 mm, nodus to pterostigma ca. 18.0 mm, pterostigma to wing apex 2.4 mm; nodus in a distinctly basal position, at ca. 28 % of wing length; pterostigma 2.6 mm long, 0.6 mm wide, with basal side very oblique, not parallel to distal side, covering five cells; pterostigmal brace oblique but distinctly less oblique than basal side of pterostigma; area between costa and RA distal of pterostigma with two rows of small cells, that between RA and RP1 with only one row of cells; nodal Cr and subnodus distinctly oblique; petiole long, 3.5 mm long, 1.7 mm wide; Ax2 opposite arculus; no secondary antenodal cross-vein distal of Ax2; no antesubnodal crossvein; 25 postnodal crossveins more or less aligned with the corresponding postsubnodal crossveins; space between arculus, base of RP3/4 and MA free; CuP distal of base of AA; AA separating from AP basal of discoidal cell; discoidal cell elongate but rather broad, 1.3 mm long, 0.7 mm wide, with its anterior and posterior sides parallel, distal side oblique, not parallel to basal side, 0.7 mm long; subdiscoidal space free, 1.9 mm long, 0.5 mm wide; a long cell below it between AA and posterior wing margin; base of RP3/4 near subnodus, 1.0 mm basal of it; base of IR2 opposite subnodus; base of RP2 10 cells distal of subnodus; base of IR1 three cells distally of that of RP2; one row of cells between RP1 and IR1; three rows and two rather long secondary longitudinal veins between IR1 and RP2, three rows between RP2 and IR2, and three rows between IR2 and RP3/4, 11 rows of cells and three long secondary longitudinal veins between RP3/4 and MA along posterior wing margin, six rows of cells and two long secondary longitudinal veins between MA and MP, area between MP and CuA very large with 20 rows of cells along posterior wing margin; four rows of cells and six secondary longitudinal veins between CuA and posterior wing margin, organized into a characteristic triadic branching pattern on CuA; all the veins ending on posterior wing margin distinctly curved.

Paratype Caт-54 ( Figure 4.3 ). The apical fourth of a wing, fragment 11.6 mm long, wing 7.5 mm wide; pterostigma 2.2 mm long, 0.7 mm wide, with basal side very oblique, with two postnodal crossveins ending on it, not parallel to distal side, covering five cells; pterostigmal brace oblique but distinctly less than basal side of pterostigma; area between costa and RA distal of pterostigma with two rows of small cells, that between RA and RP1 with only one row of cells; pattern of secondary longitudinal veins between main veins (IR1 to MA) identical to that of holotype .

Discussion. Although fragmentary, the paratype can be attributed to the same species as the holotype because of the exact identity of their patterns of venation in the preserved parts. It is of considerable interest because it completes the information on the pterostigma of this taxon. This fossil has very peculiar characters in that all the veins ending on the posterior wing margin are curved and there are numerous intercalary veins between nearly all the main veins, except between RP1 and IR1. Among the extant Zygoptera , only the Argiolestidae Fraser, 1957 (sensu Kalkman and Theischinger, 2013), the Pseudostigmatidae Kirby, 1890 , and the Thaumatoneuridae Tillyard and Fraser, 1938 have such characters. Affinities with the Argiolestidae are excluded because they all have a reduced cubital area without the triadic branching of veins between CuA and the posterior wing margin. They also have AA separating from AP well distal of the basal side of the discoidal cell ( Münz, 1919; Kennedy, 1925; Kalkman and Theischinger, 2013). The presence of secondary veins in the area between MP and CuA, the well-developed pterostigma, RA not strongly curved distal of the pterostigma, the presence of a cell between AA and the posterior wing margin below the subdiscoidal space would exclude affinities with the Pseudostigmatidae .

The Thaumatoneuridae is a small group of large damselflies that is reduced nowadays to the two Neotropical genera Thaumatoneura McLachlan, 1897 , with one living species, and Paraphlebia de Selys-Longchamps, 1862 with four living species ( Dijkstra et al., 2014). This group currently comprises some fossil taxa, viz. the Dysagrioninae Cockerell, 1908 (currently considered as a separate family Dysagrionidae , see Garrouste and Nel, 2015: Dysagrionini Cockerell, 1908 with the Cenozoic genera Primorilestes Nel et al., 2005c and Dysagrion Scudder, 1878 ; and Petrolestini Cockerell, 1927 with the Cenozoic genus Petrolestes Cockerell, 1927 and the Mesozoic genus Congqingia Zhang, 1992 ); the Cenozoic Eodysagrioninae Rust et al., 2008 ( Eodysagrion Rust et al., 2008 ); and among the Thaumatoneurinae, the sole Cretaceous genus Euarchistigma Carle and Wighton, 1990 (in Euarchistigmatini Carle and Wighton, 1990) ( Nel et al., 2005c; Bechly, 2007, 2016; Rust et al., 2008). Nel and Paicheler (1994) considered the Eocene Eothaumatoneura ptychoptera Pongrácz, 1935 , originally attributed to the Thaumatoneuridae ( Pongrácz, 1935) , as Zygoptera incertae sedis.

The modern Thaumatoneuridae do not fit well with our fossil even if Primorilestes magnificus sp. nov. shares with Thaumatoneura several characters: elongate pterostigma with a basal side very oblique, two rows of cells between Costa and RA distal of pterostigma, same pattern of supplementary longitudinal veins, all veins curved at their apices on posterior wing margin, a relatively broad anal area. There are, however, also some important differences: nodus less basally recessed, distal side of discoidal cell of normal obliquity, subdiscoidal cell free; cubital area less broad. In the distal two-third of the wings, Paraphlebia shows strong similarities with P. magnificus , the differences between them being the narrow elongate discoidal cell of Paraphlebia and AA separating from AP below the distal side of the discoidal cell ( Münz, 1919). Euarchistigma has a completely different shape of the cubital area and discoidal cell (see Bechly, 2007).

The Petrolestini Cockerell, 1927 differ from P. magnificus in characters described by Garrouste and Nel (2015), such as the broader and shorter discoidal cell and the larger and broader cubital area. In Dysagrionini Cockerell, 1908, the Cenozoic Dysagrion Scudder, 1878 differs from P. magnificus in the same characters.

Eodysagrion differs from P. magnificus in the following features given in Rust et al. (2008): distal side of the discoidal cell of inverted obliquity, longitudinal veins less curved near posterior wing margin, different shapes of the secondary veins in the cubital area; less developed area between MP and CuA.

The genus Primorilestes Nel et al., 2005c ( P. violetae Nel et al., 2005c , Early Oligocene of Primorye Territory in Russia, and P. madseni Rust et al., 2008 , Earliest Eocene of Denmark) shows strong similarities with P. magnificus in the organization of the secondary longitudinal veins between the main veins, pterostigma, positions of the nodus and bases of the main veins, and shape of the discoidal cell. P. magnificus differs from P. madseni in the larger cubital and MP areas, and in the presence of more secondary veins in the area between MA and RP3/4. The basal half of the wing of P. magnificus strongly resembles that of P. violetae , the only difference being the base of RP2 being 10 cells distal of the subnodus in P. magnificus , while it is only six cells in P. violetae . Unfortunately the distal half of the wing of P. violetae is unknown.

Thus we propose to attribute our fossil to a new species in the genus Primorilestes .

Figures

FIGURE 4. Primorilestes magnificus sp. nov. 1, holotype Сат-52 (part); 2, holotype Caт-53 (part); 3, paratype Caт-54. Scale bars represent 5 mm in all figures.