Danowhetaksa rusti Simonsen, Ware, & Archibald, 2022

Simonsen, Thomas J., Archibald, S. Bruce, Rasmussen, Jan A., Sylvestersen, René L., Olsen, Kent & Ware, Jessica L., 2022, Danowhetaksa gen. nov. with two species from the early Eocene Ølst Formation from Denmark, the first Palearctic Whetwhetaksidae (Odonata: Cephalozygoptera), Zootaxa 5099 (5), pp. 586-592 : 589-590

Danowhetaksa rusti Simonsen, Ware, & Archibald , new species

Figure 2

Material. Holotype [ MM-13418 ]: an isolated wing preserved in a concretion block, deposited in Museum Mors (Mo-clay Museum), collected by Henrik Madsen, October 31, 1993, Fur Stolleklint. The specimen was collected from a hardened bed within the upper 1.5 m of the Stolleklint clay near ash-layers -33 and -34 .

Description. Holotype wing. Arculus to distal end of pterostigma: 26.7 mm. Nodus to distal end of pterostigma: 18.9 mm. Arculus to basal end of pterostigma: 22.6 mm. Nodus to basal end of pterostigma: 14.8 mm. Width: 8.8 mm. Pterostigma dark, 5.2 mm in length, ca. 8 times longer than wide, subtends numerous cells, eight crossveins detected by preservation, surely more. Wing hyaline with transverse dark fascia, as in diagnosis, ca. 1.5 times length of pterostigma. Postnodal and postsubnodal spaces poorly preserved, but only one pair of crossveins appears aligned. IR1 very poorly preserved, origin probably zigzagged. RP2 originates 8 cells distal to subnodus. IR2 originates ca. 8/10 distance arculus to nodus, preserved part of IR2 close to linear. RP3-4 originates ca. 4/10 distance arculus to nodus, preserved part of RP3-4 close to linear. Preserved part of MA linear through fascia. Preserved part of MP linear (terminus missing). CuA linear from origin to terminus on wing margin, basal 2/3 subparallel to MA, then curving sharper to wing margin, terminates just to mid-wing beyond fascia. MA-CuA space two cells wide where CuA starts curving away, widening to at least four cells well before estimated terminus at wing margin. CuA-A space moderately well preserved, very broad, at least 5 cells wide. Quadrangle sub-trapezoid broadest distally, approximately 1.3x longer than wide. Ax0 present, synsclerotised with wing base. Arculus close to, slightly distal of Ax1. Ax2 partly preserved, ca. fifth distance arculus to nodus, just distal to quadrangle.

Diagnosis. Distinguished from D. birgitteae as in its diagnosis, above.

Deposit and age. Stolleklint clay, Ølst Formation, Stolleklint, Fur, Denmark; earliest Ypresian.

Etymology. An eponym formed by the surname of the German paleoentomologist Jes Rust, whose extensive work has greatly increased our knowledge of mo-clay insects.

Remarks. Garrouste & Nel (2015) described the monobasic Pseudostenolestidae from the latest Ypresian at Messel, Germany ( Pseudostenolestes bechlyi Garrouste & Nel ) and discussed ways in which it resembles the Dysagrionidae and Sieblosiidae (Cephalozygoptera) . It shares a distinctive quadrangle shape with the Whetwhetaksidae , which the Dysagrionidae and Sieblosiidae also possess. Notably, the arculus of P. bechlyi is positioned near Ax1 as in the Whetwhetaksidae . In P. bechlyi , the arculus and Ax1 are opposite, while in Whetwhetaksidae Ax 1 is just basal to the arculus—slightly closer to it in Danowhetaksa than in Whetwhetaksa . The pterostigma is also long in P. bechlyi , although not as long as in the Whetwhetaksidae . Unlike the Whetwhetaksidae , however, it possesses the oblique vein “O”, shared with the Sieblosiidae , and unlike the Whetwhetaksidae , Sieblosiidae , and Dysagrionidae , it has a very short petiole. Pseudostenolestes differs from the Zygoptera, Cephalozygoptera , and Whetwhetaksidae by its distinctive, strong vein Cuab originating at the middle posterior of the subquadrangle and directed towards the wing base, by which they assign it to the Isophlebioptera, previously only known from the Mesozoic.

In most Zygoptera, Ax0 is absent or obscured by sclerotization at the wing base ( Bechly 1996, and see Rehn, 2003). It is present without associated sclerotization in Whetwhetaksa and in Cephalozygoptera ( Archibald et al. 2021). In D. rusti n. sp. it is present and associated with sclerotization basally, but not obscured by it.

Figures

FIGURE 2. Danowhetaksa rusti n. sp., holotype wing [MM-13418].A, combined photograph of part and counterpart; B, drawing from part and counterpart. Short arrows indicate crossveins below pterostigma (see text). Scale bar is 5 mm.