Eotriadomeroides abjunctus Huber, 2023

Huber, John T. & Greenwalt, Dale E., 2023, A new compression fossil, Eotriadomeroides abjunctus Huber, gen. & sp. nov. (Hymenoptera, Mymaridae), in Eocene shale from the Kishenehn Formation, USA, Journal of Hymenoptera Research 96, pp. 657-666 : 657

Eotriadomeroides abjunctus Huber sp. nov.

Figs 1-2 , 3-5 , 6, 7 , 8

Material examined.

Holotype female (NMNH), on 18 × 14 × 0.15 cm piece of oil shale (Fig. 9 ), labelled " Holotype Eotriadomeroides abjunctus Huber. USNM # PAL 620738". The circle/square scratched onto the surface of the shape indicates the holotype location. The specimen was collected in 2012 at locality #43946, Park site, Kishenehn Formation, Montana, USA.

Diagnosis.

Eotriadomeroides abjunctus is the only described species in the genus. Its diagnosis is therefore the same as for the generic description. Comparing it with species of morphologically similar genera, it differs from all the described species of Neotriadomerus ( Huber 2017) as follows: clava 1-segmented (clava 3-segmented in Neotriadomerus species); postmarginal vein ~2.7 × as long as parastigma + marginal vein + stigmal veins (postmarginal vein at most 0.90 × as long in Neotriadomerus species); hind wing narrow and apically acute (hind wing wide and apically blunt in Neotriadomerus species). The apparent absence of a straight setal line extending from apical margin of fore wing about halfway towards the parastigma + marginal veins (Fig. 7 ) is an additional feature that may separate E. abjunctus from Neotriadomerus but the wing surface of E. abjunctus is not clear enough to be sure if the setal line is absent. Eotriadomeroides abjunctus differs from Triadomerus bulbosus Yoshimoto by the clava 1-segmented (3-segmented in T. bulbosus ), ovipositor extending ventral to mesosoma as far as head (ovipositor not extending anteriorly ventral to mesosoma in T. bulbosus ), and relatively longer postmarginal vein (relatively shorter in T. bulbosus ).

Description.

Female. Color. Vertex, antenna except radicle, dorsum of body, except for scutellum, and ovipositor sheaths dark brown or almost black; face, radicle, scutellum, and mesosoma and metasoma ventrally apparently lighter brown (Fig. 1 ). Total body length ~2850. Head. Head length ~205, head width ~600; mid ocellus diameter ~35. Antenna (Figs 2 - 5 ). Three (possibly 4) mps are visible on the right clava and one on fu8 of the left antenna (Fig. 5 ); the mps that most likely should occur on the remaining funicle segments are not visible. Length/width measurements: range (ratios) of antennal segments: radicle? ~85/~12 (2.08), scape excluding radicle ~230/~90 (2.53), pedicel ~75/~50 (1.47), fu1 ~170/~45 (3.85), fu2 ~160/~40 (3.83), fu3 ~150/~40 (3.67), fu4 ~150/~45 (3.33), fu5 ~140/~40 (3.08), fu6 ~150/~40 (3.60), fu7 ~135/40 (4.00), fu8 ~125/~150 (2.57), clava ~325/~85 (3.76). Mesosoma. Mesosoma length ~900, metanotum with dorsellum almost certainly triangular (Fig. 6 ). Wings. Fore wing (Fig. 7 ) with microtrichia uniformly covering entire surface, apparently to base of parastigma and apparently with one row of a few microtrichia posterior to apex of submarginal vein; fore wing length/width ~1930/~560, length/width 3.50, longest marginal setae ~80; hind wing length ~ 1150, width ~45, longest marginal setae ~115, with wing apex acute. Legs. Tarsi 5-segmented, the tarsomeres becoming shorter towards apex of tarsus (legs segments mostly unrecognizable except two tibiae in part and two tarsi visible, with the end points of basal tarsomeres unclear). Metasoma. Petiole (Fig. 6 ) evidently short; gaster with terga apparently about equal in length. Metasoma length ~1875; ovipositor length ~2640, with sheaths extending anteriorly ventral to mesosoma to level of pronotum.

Derivation of species name.

From the Latin abjunctus, meaning disunited or separated, refers both to the strongly disjunct geographic distribution of this 40 my old fossil from extant members of Neotriadomerus , the most similar looking genus, and to the fact that some of the fossil’s appendages are broken into parts (the antennae) or are separated from the body (the legs).

Figures

Figures 1, 2. Eotriadomeroides abjunctus Huber, holotype female 1 habitus (except most legs not visible) 2 pronotum + head + partly disarticulated antennae.

Figures 3 - 5. Eotriadomeroides abjunctus Huber, holotype female 3 head + part of antennae 4 left antenna (pedicel-fu 5) 5 fu 8 + clava of both antennae.

Figures 6, 7. Eotriadomeroides abjunctus Huber, holotype female 6 mesosoma 7 wings + metasoma.

Figures 8, 9. Eotriadomeroides abjunctus Huber, holotype female 8 tibiae and tarsi of one? pair of legs 9 shale piece containing holotype (circled) of Eotriadomeroides abjunctus Huber.