Megalomus

Jepson, James E. & Makarkin, Vladimir N., 2023, Fossil Neuropterida (Insecta: Neuroptera and Raphidioptera) from the middle Eocene Kishenehn Formation, Montana, USA, Zootaxa 5306 (4), pp. 427-444 : 435-437

Megalomus -group gen. et sp. indet.

Fig. 5

Material. Specimen USNM PAL 624842, deposited in USNM. An incomplete specimen.

Locality and horizon. Middle Fork of the Flathead River, between Paola and Stanton Creeks approximately 17 miles south of West Glacier; the Coal Creek Member of the Kishenehn Formation, north-western Montana, U.S.A. The Middle Eocene (Luteian).

Description. Body poorly preserved, fine details not discernable. Head poorly preserved, only both eyes well discernible (0.5 mm wide). Prothorax 0.6 mm long, mesothorax 1.5 mm long, metathorax 0.8 mm long. Legs and abdomen not preserved.

Forewing fragmentary, poorly preserved, ca. 6.8 mm long (as preserved; estimated complete length ca. 8 mm), 2.7 mm wide (as preserved; estimated width ca. 3 mm). Recurrent humeral veinlet well developed, with four preserved branches. Costal space narrowing distally, with ca. 15 partially preserved costal veinlets, mainly forked; trichosors present on costal margin. Sc and RA partially preserved; subcostal crossveins not detected. RP poorly preserved, with five to six branches separately originating on RA. RP1 at least deeply-forked once near origin. Three gradate series of crossveins partially preserved. Second series consists of two preserved crossveins (right wing), between M and CuP. Third (‘inner’) series consists of eight preserved crossveins anterior to CuA (probably nine in life) (left wing); fourth (‘outer’) series with four preserved crossveins (left wing). M forked nearly opposite fork of RP1; posterior branch probably forked again at inner gradate series. Cubital veins fragmentarily preserved; proximal branch of CuA originating at second gradate series. Anal veins not preserved.

Hind wing fragmentarily preserved, 5.5 mm long (as preserved; estimated complete length ca. 7 mm), 1.8 mm wide (as preserved; estimated complete width ca. 2.4 mm). Costal space narrow, narrowest at mid-way point. Costal veinlets partially preserved, proximally simple, distally few forked; trichosors preserved on costal margin. Subcostal space narrow. Sc and RA partially preserved, not fused; reaching wing margin before apex. RA distally with three to four branches. RP partially preserved, at least with five branches. Third (‘outer’) gradate series with five preserved crossveins. Cubital and anal veins not preserved.

Remarks. This specimen obviously belongs to a genus of the Megalomus -group (Drepanepteryginae, Drepanacrinae or Megalominae). These hemerobiids share the wing character states such as a dense venation; a deeply forked CuP in the forewing; and a fully developed CuP in the hind wing (see Makarkin et al. 2016 for detailed discussion). The venation of the specimen is fragmentarily preserved, and it is therefore difficult to place into a particular genus. However, the preserved venation is most similar to that of Proneuronema Makarkin et al. 2016 , in particular the presence of at least once deeply-forked RP1. This genus was widely distributed in the Eocene in North America, Europe, and East Asia (see Makarkin & Perkovsky 2020).

Figures

FIGURE 5. Megalomus-group gen. et sp. indet., specimen Holotype USNM PAL 624842. A, specimen as preserved; B, left forewing venation; C, left hind wing venation; D, right forewing venation; E, right hind wing venation. Scale bar 1 mm.