Sinowhetaksa incompleta Nel sp. nov.

urn:lsid:zoobank.org:act: 5500D7E4-A836-4A4D-821F-317199603CFC

Material. Holotype, a fragmented wing attached to thorax (Fig. 7), NIGP200692, stored at NIGPAS.

Etymology. Named after the incomplete state of preservation of the holotype.

Diagnosis. As for the genus.

Locality and horizon. Ningming Formation; along the Luoyue Avenue, Chengzhong Town, Ningming County, Chongzuo City, Guangxi, China; early Oligocene (Rupelian).

Description. Wing hyaline with brown pterostigma; wing ca. 27.0 mm long, ca. 7.7 mm wide; petiole rather short, 2.9 mm long; CuP just basad base of AA; anal area narrow below subdiscoidal cell, with one row of cells; distance from base to nodus 6.6 mm; from nodus to pterostigma 14.2 mm; from pterostigma to wing apex ca. 1.9 mm; pterostigma elongate, 3.3 mm long, width between 0.6 mm and 0.8 mm (the vein RA along its posterior margin compressed and deformed so that the pterostigma seems to be wider than it should be); basal side of pterostigma very oblique; distal side even more oblique and very long, with a distinct ‘prolongation’ along costal margin, 0.3 mm long; one row of cells in area between C and RA just distad pterostigma but two rows distally; no oblique pterostigmal brace; 19 postnodal crossveins, basal-most ones being well aligned with postsubnodal crossveins and distal ones not aligned; nodal crossvein and subnodus well aligned and strongly oblique; base of RP2 five cells distad subnodus; base of IR1 ca. six cells distally; base of IR2 one cell basad nodus; CuA terminating at margin over half wing length, well distad nodus; MA close to, subparallel with RP3-4 to posterior margin; MA and MP diverging to posterior margin; MP and CuA subparallel to posterior margin.

Remarks. Although fragmentary, this wing is attributed to Zygoptera sensu lato because of the presence of a petiole, shape of subdiscoidal cell, and very long postnodal area. It does not fit in the epiproctophoran Isophlebioptera Bechly, 1996 that have also these characters, because of the narrower anal area and subdiscoidal cell. This last clade was still present during the Eocene through the family Pseudostenolestidae (Garrouste & Nel, 2015). There are rather few damselfly families with such broad wings, elongate pterostigma, long postnodal area compared to antenodal one, and so numerous postnodal crossveins, viz. the Dysagrionidae, Sieblosiidae, Whetwhetaksidae, Shundeagrionidae, Menatlestidae, Latibasaliidae, Thaumatoneuridae, and Heliocharidae.Affinities with the Heliocharidae are excluded because of the longer petiole, and base of IR2 close to nodus; affinities to Thaumatoneuridae are excluded because the base of RP2 is only five cells distad subnodus (Münz, 1919).Affinities with the Sieblosiidae are excluded because the subnodus is in straight line with the nodal crossvein and of strong ‘normal’ obliquity, and the base of IR2 is one cell basad the nodus. Affinities with the Shundeagrionidae, Menatlestidae, and Latibasaliidae are excluded because the base of IR2 is one cell basad nodus vs midway between nodus and arculus, and distal side of the pterostigma is strongly oblique vs much less in the latter groups (Petrulevičius & Nel, 2007; Nel & Jouault, 2022; Huang et al., 2025). Affinities with the Dysagrionidae are excluded because the subnodus is much more oblique than in this family (with a weak ‘normal’ obliquity to perpendicular to RP in the Dysagrionidae) (Archibald et al., 2021: figs 67- 67; Simonsen et al., 2022: figs 1A, 2A). Also the distal side of the pterostigma of the new fossil has a very particular shape, very oblique with a short but distinct ‘prolongation’ along costal margin. This character is present in the Whetwhetaksidae, but not in the other families, even if some Dysagrionidae (e. g., Okanagrion, Dysagrion) also have an oblique distal side of the pterostigma, but less than in the new fossil and the Whetwhetaksidae, and no costal ‘prolongation’. This character is not listed in the diagnoses proposed by Archibald et al. (2021: 110), Simonsen et al. (2022: 587), and Ware et al. (2025) for the Whetwhetaksidae, but it is a putative synapomorphy for this family, present in the type genus Whetwhetaksa and in Danowhetaksa.

The preserved characters of the new fossil fit well with those listed in the diagnoses of this family, viz. distinctively long pterostigma [Simonsen et al. indicated ‘length at least seven times width’, while it is five to eight times, depending if we count the width of the vein RA along its posterior margin in the new fossil, but this character can greatly vary in representatives of the same family, e. g., see the different situations in the Dysagrionidae]; nodus to base of pterostigma 55–60% of nodus to apex [75% in the new fossil, due to the slightly shorter pterostigma]; arculus just distal to Ax1, closer to it than to Ax2 [unknown in the new fossil]; oblique vein O absent [probably shared by the new fossil]; nodal, subnodal crossveins of ‘normal’ obliquity [shared by the new fossil]; base of RP2 close to nodus [shared by the new fossil]; CuA terminates at margin over half wing length [shared by the new fossil]; MA close to, subparallel with RP3-4 to margin [shared by the new fossil]; MA and MP diverge to margin [shared by the new fossil]; MP and CuA remain subparallel to margin [shared by the new fossil].

In conclusion, the new fossil can be attributed to the Whetwhetaksidae, especially because of the specialized shape of the distal margin of the pterostigma.

Its base of RP2 is five cells distad subnodus, vs. only two to four cells in Whetwhetaksa, and eight cells in Danowhetaksa. It also has only 19 postnodal crossveins, vs. ca. 20 in Whetwhetaksa, and ca. more than 25 in Danowhetaksa. Its base of IR2 is one cell basad the nodus, vs. in a well basal position in Whetwhetaksa and two small cells basad in Danowhetaksa. Lastly, there is only one row of cells in area between C and RA just distad the pterostigma, vs. two rows in Whetwhetaksa and Danowhetaksa, but this last character is more of species level than the preceding.

It is not very surprising to find a representative of the Whetwhetaksidae in China as this family is present in the Paleogene of Eastern North America and Western Europe. This group is either quite ancient, Cretaceous or probably could ‘migrate’ between Eurasia and North America through the ‘Beringian Bridge’ as for some other Odonata (Garrouste & Nel, 2019).