Stenodiafanus 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 : 101-102

Stenodiafanus Archibald & Cannings , new genus

Fig. 61 .

Diagnosis. Wings distinct from other Dysagrioninae except Okanopteryx by: pterostigma length 4 times width [distinct from Okanopteryx : 2–2.5 times; Furagrion : 3; Primorilestes : 3.5; Phenacolestes : 4.5–5; not distinct from Dysagrion : 3–7.5; Stenodiafanus : almost 4; Okanagrion : 3–3.5, rarely 4; Dysagrionites species: unknown]; oblique brace vein present [separated from Okanagrion , Phenacolestes , Primorilestes , not present; not distinct from Dysagrion , Furagrion, Okanoptyeryx : present; Electrophenacolestes , Dysagrionites species: unknown, wing region not preserved]; costal space 2 cells wide distal to pterostigma [distinct from Dysagrion , Furagrion , Phenacolestes : all 1; Okanagrion : 3–5; shared by Primorilestes , Okanopteryx : both 2; Electrophenacolestes , Dysagrionites species: not known]; subnodus with normal obliquity [separated from Dysagrion : reversed obliquity; all others: normal obliquity, slight to notable]; no accessory antenodal crossveins [distinguished from Phenacolestes , Electrophenacolestes , some Dysagrion species: with; not distinguished from others: without]; IR2 origin between RP1-2, RP3-4, connected to RP1-2, RP3-4 at similar level [ Dysagrion : between RP1-2, RP3-4, but closer to RP3-4, connected with RP1-2 distinctly more distally than to RP3-4; not distinct from other genera, except some Okanagrion species: origin close to or on RP1-2]; MA zigzagged from mid-wing to margin [distinct from Okanagrion , Primorilestes , Electrophenacolestes (very end not preserved): linear or nearly so; Phenacolestes : very slight zigzag in middle; Dysagrion: MA becomes zigzagged mid-wing, then linear near margin; Furagrion : slightly zigzagged mid-wing then linear, deeply curved to margin]; MA, MP close at margin, probably separated by 1–2? cells (difficult to be sure of exact identity of MA near margin by strong zigzag) [distinct from Okanagrion , Furagrion , Primorilestes , Electrophenacolestes : widely separated; not distinct from Dysagrion : 1–2 cells apart; Okanopteryx : identity of MA near margin also unsure by strong zigzag, but close to MP; Dysagrionites species: also difficult to establish, perhaps one cell apart?]; CuA zigzagged from to about mid-wing to margin (but proximal to this not known) [distinct from Electrophenacolestes , Primorilestes , Okanagrion : linear or only very slightly zigzagged; Furagrion : slightly zigzagged distal to level of origin of RP2; Phenacolestes : very slightly zigzagged in parts or not; not distinct from Dysagrion , Okanopteryx : increasingly zigzagged distal to level of nodus or from Dysagrionites species as known, but distal-most portions not preserved]; CuA–A space 2 cells wide [separated from Phenacolestes , Dysagrion , Electrophenacolestes : 4; Primorilestes : 3–5; Okanagrion , 4–7; Dysagrionites sp. B: probably 3 but unclear; not separated from Okanopteryx : 2–4; Furagrion : 2; Dysagrionites sp. A: 2]; distinct from all other Dysagrionidae genera except Okanopteryx by RA, RP1, IR1, RP2 distinctly converge, almost meeting at apex; postnodal, postsubnodal crossveins mostly aligned at least in proximal half [distinct from Phenacolestes , Primorilestes madseni , Dysagrion : all not; not separated from Okanopteryx , Primorilestes violetae ; Electrophenacolestes ; Furagrion : similar]; hyaline throughout (sex unknown) [males (females unknown) of Okanopteryx , most Okanagrion : with various colour patterning; not separated from Dysagrion : hyaline (sex unknown)]; shape long, 24.8 mm nodus to apex, narrow, 5.8 mm wide, with a rather acute, elongate apex [ Okanopteryx from holotype O. macabeensis : 18.4 mm nodus to apex, 6.5 mm wide to O. jeppesenorum paratype 1 (SR 11-43-09): 23.5 mm nodus to apex, 7.2 mm wide, holotype (SR 13-005-013): 7.7 mm wide]; further distinct from Primorilestes by no intercalary vein in CuA–A space. Separated most easily from Valerea (tentative Dysagrioninae ) by no linear supplementary sector between RP1, IR1 [ Valerea : with such sector]; costal space 2 cells wide distal to pterostigma [maximum 5]; origins of IR1, RP2 further from nodus; origin of IR2 between RP1-2, RP3-4 [IR2 origin not preserved, only preserved distal to level of nodus, where it is closer to RP3-4]. Most easily separated from genera regarded here as possible Dysagrionidae as follows: from Chickaloon specimen ( Garrouste & Nel 2019) by CuA zigzagged distally to margin (proximal portion not preserved) [linear in all preserved portion to near terminus]; CuA–A space 2 cells wide [4]; from Thanetophilosina by no linear sectors between RP1, IR1, between IR1, RP2 [with], by pterostigma length 4 times width [about 6]; from NHMUK I.9866/I.9718 by origin of RP3-4 [distinctly closer to subnodus]; from cf. Dysagrionidae genus A, species A (“ Megapodagrionidae ” genus A, species A, Petrulevičius et al. 2008) by hyaline membrane [preserved portion infuscate except apex distal to pterostigma], by MA, CuA zigzagged distally to margin [linear to margin], by pterostigma length 4 times width [about 2.5], by width 23% length nodus to apex [37%].

Type and included species. Stenodiafanus westersidei , type and only species.

Description. As in diagnosis and the description of its only species, below.

Etymology. The genus name is formed from the Greek στενóς, stenos, meaning “narrow”, and Διαφανής, diafanis, meaning “transparent”, referring to their slender, hyaline wings. Gender, masculine.

Range and age. Okanagan Highlands, Tom Thumb Tuff Member of the Klondike Mountain Formation, at Republic, Washington, USA; late Ypresian.

Figures

FIGURE 61. Stenodiafanus westersidei holotype, SR-06-01-42. A, photograph; B, drawing. Both to scale, 5 mm.