Okanagrion dorrellae Archibald & Cannings, 2021

Archibald, Bruce, Cannings, Robert A., Erickson, Robert J., Bybee, Seth M. & Mathewes, Rolf W., 2021, The Cephalozygoptera, a new, extinct suborder of Odonata with new taxa from the early Eocene Okanagan Highlands, western North America, Zootaxa 4934 (1), pp. 1-133 : 68

Okanagrion dorrellae Archibald & Cannings , new species

Fig. 37 .

Diagnosis. Wings separated from those of all other species of Okanagrion by MP zigzagged in distal portion [all others: linear (but not known in O. angustum )]; from all but O. angustum by narrower shape, especially in the proximal portion: maximum width 7.0 mm [ O. threadgillae : forewing, hind wing: 9.0 mm; O. hobani all wings: 8.2–9.5 mm; O. beardi : 7.7, 8.3 mm; O. liquetoalatum : forewing 8.5 mm; O. worleyae : about 7.8 mm], wing length (arculus to apex) / width, 3.7 [ O. hobani : 3.2; O. threadgillae : forewing 3.0, hind wing 3.1; O. beardi : forewings 3.3, 3.4, O. liquetoalatum : forewing 2.6 ( O. lochmum , O. worleyae , O. angustum not comparable by preservation)]; from O. hobani by main veins less deeply curved near margin; from O. angustum , O. beardi by IR2 origin between RP1-2, RP3-4 [ O. angustum , O. beardi : origin on RP1-2]; from O. lochmum by cells less dense in apical portion of wing: see RA–RP1 space becomes two cells wide, three cells wide, four–five cells wide as it its diagnosis; from all other Okanagrion species but O. beardi by MP, CuA divergent near margin [others: MP-CuA space remaining narrow; O. beardi : distinctly divergent, O. dorrellae : less distinctly as CuA zigzagged distally ( O. angustum , not known)].

Further separated by colouration (sex unknown): proximal near half hyaline, dark apical to this except lighter fascia just distal to mid-way between nodus, pterostigma, extending from anterior margin to apparently mid-wing (some damage); size and extent of light fascia differs from: O. hobani about twice or more as wide, extending to or almost to posterior margin; O. angustum apparently similar to O. hobani as preserved; O. threadgillae narrower, extends to mid-wing; O. beardi , O. lochmum , similar width, apparently extends closer to posterior margin; O. liquetoalatum : hyaline throughout; O. worleyae : lightly infuscate throughout known wing.

Type material. Holotype: SR 93-11-02 ( Fig. 37 ), collected Republic B9201 by Laurie Dorrell, 31.x.1992, a complete wing except for diagonal break across mid-section, with colour patterning; SR collection.

Description. Holotype, SR 93-11-02, wing. Shape: oval distal to nodus, symmetrical to lateral mid-line, but apex slightly posterior to this. Length: arculus to apex: 25.6 mm, nodus to apex: 21.1 mm, origin of RP2 to apex: 16.5 mm, arculus to base of pterostigma: 19.7 mm, nodus to base of pterostigma: 15.3 mm, nodus at 26% wing length; width 7.0 mm. Colouration as in diagnosis. Pterostigma incompletely preserved, region of possible oblique brace vein not preserved. 35 crossveins in postnodal space (total), those in postsubnodal space not aligned. At least three cells wide maximum in costal space distal to pterostigma, but most of space not preserved. RA meets margin anterior to apex. RA–RP1 space narrows near margin. IR1: origin nine cells distal to origin of RP2, IR1 two cells wide probably (poorly preserved) eight cells distal to origin. RP2: origin seven cells distal to origin of IR2 (one very small). IR2: origin at subnodus. RP3-4 origin in distal part of middle third between arculus, nodus. Arculus just proximal to Ax2. No crossvein O. All main veins linear except base of IR1, MP distal to mid-wing between nodus, pterostigma. CuA–A space apparently (by preservation) five cells wide at widest.

Etymology. The specific epithet is a patronymic formed from the surname of Laurie Dorrell, the collector of the holotype, recognising her contribution.

Range and age. Republic locality B9201 of the Tom Thumb Tuff Member of the Klondike Mountain Formation; latest Ypresian.

Discussion. Although the holotype wing and sole specimen of O. dorrellae has a diagonal break across it, we are confident of the shape as the veins are not shifted across this break. The wing has not been compressed, as internal elements such as the shape of cells are not deformed.

Figures

FIGURE 37. Okanagrion dorrellae holotype, SR 93-11-02. A, photograph; B, drawing. Both to scale, 5 mm.