Dysagrionites allenbyensis, Archibald & Cannings, 2024

Archibald, S. Bruce & Cannings, Robert A., 2024, Three new Odonata species (cf. Cephalozygoptera and cf. Dysagrionidae) from the early Eocene Okanagan Highlands of British Columbia, Canada, and Washington, United States of America, The Canadian Entomologist (e 35) 156, pp. 1-9 : 4-5

Dysagrionites allenbyensis sp. nov.

ZooBank Registration number: urn:lsid:zoobank.org:act:E1F8815D-1BB4-4090-99EE-08A9273CEE79

Figure 1

Type material. Holotype BBM-P 000020 A and B (part and counterpart). A well-preserved wing with colouration, missing the apical portion. Found by Beverley Burlingame on 2 April 2024 and donated to the Beaty Biodiversity Museum, where it is housed .

Diagnosis. The wing of Dysagrionites allenbyensis is most like those of Okanopteryx Archibald and Cannings (three species as discussed below) and Stenodiafanus Archibald and Cannings (one species as discussed below). It is distinct from those of Okanopteryx by: CuA space expanded to three cells wide for much of its length from subquadrangle to terminus [ O. jeppesenorum Archibald and Cannings maximum four; O. fraseri Archibald and Cannings usually two, sometimes a single row of three]; pigmented fascia wide, extending from nodus to at least 15 and probably 17 cells beyond it [ O. macabeensis Archibald and Cannings nine (holotype) to 11]. It is distinct from Stenodiafanus westersidei Archibald and Cannings by dark fascia [ S. westersidei : hyaline throughout] and CuA space width [ S. westersidei : maximum two cells in equivalent region preserved].

Description. As above and the following: RP3–4 origin at two-thirds the distance from arculus to subnodus. Postnodal and postsubnodal crossveins almost all aligned. Apex of wing and pterostigma unknown by preservation. No oblique crossvein O. CuA progressively zigzagged in distal quarter; MA zigzagged in distal third (final portion not fully preserved); IR1 almost linear from its origin three cells from origin of RP-2; other main veins linear (but distal portions missing). CuA space expanded in the middle, three cells wide for most of its length. Ax1, Ax2 preserved, arculus aligned with Ax2; subnodus distinctly angled, normal obliquity. Membrane hyaline except for dark fascia mid-wing from nodus to the level of at least 15 postnodal crossveins and probably 17 in total. Geologic shear forces may at times somewhat distort fossils at this exposure, and so the apparent narrowness of the wing might be an artefact ( Archibald and Cannings 2021b; Archibald et al. 2023a).

Etymology. The specific epithet is a toponym referring to the Allenby Formation.

Range and age. Vermilion Bluffs Member of the Allenby Formation about 4 km southwest of the village of Princeton, British Columbia. Ypresian (see above).

Remarks. Dysagrionites allenbyensis is immediately notable for its broad, dark fascia mid-wing. Within the Dysagrionidae , such colouration is found only in species of Okanopteryx (Archibald et al. 2021) . The genus is known by three species from Okanagan Highlands localities: O. macabeensis (type species) and O. fraseri from the McAbee locality near Cache Creek, British Columbia, and O. jeppesenorum from Republic, Washington (Archibald et al. 2021). Okanagrion hobani Archibald and Cannings ( Dysagrionidae ) is also known from both Republic and McAbee but has not been found in the Allenby Formation.

The preserved veins of BBM-P000020 agree with those that, in combination, are partly diagnostic of Okanopteryx : no accessory antenodal crossveins; the subnodus is distinctly angled, with normal obliquity; the origin of IR2 is rather evenly spaced between RP1–2 and RP3–4; MA is linear to mid-wing, then becomes increasingly zigzagged; MA and MP are close at margin; CuA is increasingly zigzagged from about mid-wing; the postnodal and postsubnodal crossveins are almost all aligned; and there is no intercalary vein in the CuA–A space. However, other character states necessary to assign a wing to the genus in combination with the above cannot be evaluated on this incomplete fossil: the shape and size of the pterostigma; presence of an oblique brace vein; number of cells wide in the costal space distad the pterostigma; and a distinct convergence of RA, RP1, IR1, RP2 at apex. Dysagrionites allenbyensis does not greatly differ from O. macabeensis in particular and could be a regional variant of that species, close in distance (ca. 150 km) and time (age estimates overlap: McAbee: 52.10 ± 0.26 Ma, Vermillion Bluffs: 51.85 ± 0.85 Ma; both Rubino et al. 2021).

These preserved character states are also found in Stenodiafanus (see diagnosis in Archibald et al. 2021). The broad, dark fascia of BBM-P000020 might easily be present convergently in a species of that genus, and the width of the CuA space could vary among its species as it does among those of Okanopteryx . Stenodiafanus westersidei is known only from the Klondike Mountain Formation, about 150 km distant and close in time (estimated ages overlap: Klondike Mountain B4131 at 51.18 ± 0.09 Ma and Vermillion Bluffs as above; both Rubino et al. 2021). McAbee, the Allenby Formation, and the Klondike Mountain Formation had similar climates and forests ( Greenwood et al. 2005; Archibald et al. 2011).

Figures

Figure 1. Dysagrionites allenbyensis n. sp. A, holotype BBM-P000020: A, photograph of the part (A-side); B, drawing from the part and counterpart. Both to scale; the scalebar is 5 mm.