Kishenehna, Archibald & Cannings & Greenwalt, 2022

Archibald, S. Bruce, Cannings, Robert A. & Greenwalt, Dale E., 2022, Kishenehna prima, a new genus and species of darner dragonfly (Odonata, Aeshnidae, Gomphaeschninae) from the early middle Eocene Kishenehn Formation of Montana, USA, Zootaxa 5099 (4), pp. 496-500 : 497-498

Kishenehna new genus Archibald & Cannings

Diagnosis. The female hind wing of Kishenehna n. gen. is most like those of Alloaeschna Wighton & Wilson. Kishenehna is excluded from Aeshninae sensu von Ellenrieder (2002), by MA, RP3-4 parallel where one cell width becomes two (her character state 13.1), Mspl lacking concave bend in distal portion (her character state 14.2); and differs from all remaining Aeshnidae other than Alloaeschna by a combination of an unbranched IRP2 (shared by all Alloaeschna ); RP2 curved basal to pterostigma (shared by all Alloaeschna ); radial, medial planates, MP–CuA space narrow, each one cell wide (shared by most Alloaeschna : last row at margin in some, a few adventitiously more basally in some specimens; A. quadrata Wighton & Wilson : MA–CuA terminus poorly known by preservation; A. marklae Wighton & Wilson : medial planate two cells wide for five? rows to margin); radial planate expanded slightly in middle (all Alloaeschna : slightly or not expanded); without crossveins in supratriangle (shared by all Alloaeschna except A. marklae , 1 crossvein), subtriangle (shared by all Alloaeschna ); no cordulegastrid gap ( Alloaeschna : see Discussion, below).

Hind wings of Kishenehna are separated most easily from those of Alloaeschna by anal loop with four cells [ Alloaeschna : six]; by RP2–IRP2 space maximum of three cells wide from level of base of pterostigma to cell row at margin [ Alloaeschna : two cells wide (except a few cell rows at margin)].

The following genera are only known from partial/damaged fossil wings; all character states discussed above cannot be evaluated.

Cretalloaeschna Jarzembowski & Nel (based on a partial forewing, see Jarzembowski & Nel 1996) differs by two rows of cells in RP2–IRP2 space [ Kishenehna : three cells wide distal to level of mid-pterostigma (except at margin)]; one row in RP3-4–MA space but two close to margin [ Kishenehna : two cells wide more basally].

Cretagomphaeschnaoides Zheng et al. (based on a fragmentary forewing, see Zheng et al. 2016) differs by estimated wing length 27–29 mm [ Kishenehna : 39 mm]; discoidal triangle three-celled [ Kishenehna : two]; three aligned antenodal crossveins present immediately basal of nodus [ Kishenehna : these not aligned].

Kachinaeshna Zheng et al. (based on most of a forewing, portion of a hind wing, see Zheng et al. 2019) differs by MP–CuA space dividing to two cells width near margin [ Kishenehna : one to margin]; IRP1 origin at brace vein [ Kishenehna : 1.5 cells basal to this]; forewing 31.1 mm long [ Kishenehna : 36 mm].

UAPC 6190 (unnamed base of hind wing from Paleocene of Alberta: Wighton & Wilson 1986) by anal loop with ten cells [ Kishenehna : four]; triangle with four cells [ Kishenehna : two]; subtriangle with crossveins [without].

Idemlinea Archibald & Cannings (2019 , based on basal portion of a hind wing) differs most notably by basal portions of MP, CuA parallel to hind margin [curves toward it]; supratriangle about 4.5 times longer than wide [ Kishenehna : about six times].

Type species. Kishenehna prima n. sp. by monotypy.

Description. As for its only species, below.

Etymology. The genus name Kishenehna is the Latinized form of “Kishenehn”, referring to the formation. Gender, feminine.

Range and age. As for its only species, below.

Discussion. We assign Kishenehna to the Aeshnidae by its distinct radial and medial planates and well-developed hind wing anal loop. We exclude the subfamily Aeshninae as in the genus diagnosis. Gomphaeschninae are not strongly defined by wing characters, none of which are found to be consistent throughout the taxon, which von Ellenrieder (2002) defined by male secondary genitalia. We associate the new genus with the Gomphaeschninae by its strong similarity to Alloaeschna .

Kishenehna lacks a cordulegastrid gap, considered an important trait in associating wings of many Gomphaeschninae , although it is not present in all assigned to it ( Bechly et al. 2001, von Ellenrieder 2002), is weakly to very weakly expressed in some, and is present in a species of the Cretaceous Liupanshaniidae ( Bechly et al. 2001) . The forewing of Alloaeschna quadrata lacks it (hind wing unknown), and its presence appears variable in A. paskapooensis Wighton & Wilson. It is arguably absent in the hind wing specimen UAPC 6183 ( Wighton & Wilson 1986, figure 8).

The radial and medial planates and MP–CuA spaces a single cell wide, the oblique vein O as the first crossvein distal to the origin of RP2, and the hypertriangle and subtriangle without crossveins are conditions found in numerous Gomphaeschninae , sometimes together, as in, e.g., Gomphaeschnoides obliquus Wighton, see Wighton (1987, figure 2, as Gomphaeschna obliqua ), which also has its triangle crossed by a single crossvein, but which differs in other ways, e.g., by bearing a distinct cordulegastrid gap.

Alloaeschna fossils are known from the middle or late Paleocene Tiffanian North American Land Mammal Age ( Hoffman & Stockey 1999) of the Paskapoo Formation of Alberta, Canada, about 10–16 million years older than the Coal Creek Member and some 440 kilometers to the north.