Monoblastus? senilis (Brues, 1910) Spasojevic & Broad & Klopfstein, 2022

Spasojevic, Tamara, Broad, Gavin R. & Klopfstein, Seraina, 2022, Revision of 18 ichneumonid fossil species (Hymenoptera, Ichneumonidae) highlights the need for open nomenclature in palaeontology, Fossil Record 25 (1), pp. 187-212 : 187

Monoblastus? senilis (Brues, 1910) comb. nov.

Fig. 16

* Pimpla senilis Brues, 1910

Material.

Photographs of the holotype (part only, #PALE-2160) obtained from the MCZ.

Stratum.

Teller County, Florissant shales, Colorado, USA. Late Eocene (Chadronian), 37.2-33.9 Ma.

Description.

Female. Holotype in lateral to ventro-lateral view, with head, base and tip and some intermediate segments of antennae, mesosoma, fore and nearly complete hind wings, hind legs, metasoma and ovipositor with sheaths. Body length 8.0 mm.

Colouration unclear, as with irregular dark and lighter patches on head, mesosoma and metasoma which are probably a preservation artefact but with what looks more real orange colouration on parts of pronotum, last sternites and legs. Hind tibia with apex darkened. Tergites of metasoma with apical third to half of lighter colour.

Head with rather long gena, thus almost globular in shape. Antennae 6.2 mm, with more than 30 (probably about 45) flagellomeres, tapering strongly on last third of its length, with basal segments longer than wide and apical segments transverse. Mesosoma stout; pronotum probably with strong epomia; mesoscutum rather short, maybe with notauli, with short carinulae on outer side; mesosternum with deep medial sternal groove with transverse carinulae; epicnemial carina curved and reaching up to about mid-height of mesopleuron. Propodeum short, not well preserved, with pleural and submetapleural and probably additional carination present. Fore wing 5.35 mm, with areolet quadrate and slightly oblique, receiving 2m-cu a bit apical of its centre, 4M thus shorter than 3M; 1cu-a meeting 2Cu distinctly after 1M; 3Cu a little longer than 2cu-a; vein 1m-cu & 2Rs+M conspicuously bowed; cell 2R about 3.5 as long as wide. Hind wing with 1Cu a bit longer than 1cu-a and 1Rs about 1.6 × longer than rs-m. Legs of normal dimensions, hind femur 3.6 × longer than wide, hind tibia with two slender spurs. Metasoma with T1 clearly longer than wide, with strong lateral and laterodorsal carinae and probably deep glymma, with dorsal longitudinal carinae at least present on basal half and with some longitudinal carinulae; T2 a bit longer than wide, following tergites subquadrate, all with what look like rather deep punctures; hypopygium rather prominent, triangular. Ovipositor about 1.5 mm, 1.3 × as long as hind tibia, parallel sided and down-curved; ovipositor sheaths evenly hairy and somewhat expanded around middle.

Interpretation.

The deep glymma, bowed vein 1m-cu & 2Rs+M in the fore wing, and shape of the metasoma suggest membership in Tryphoninae , where the down-curved ovipositor and possibly medially expanded sheaths point to genera such as Thymaris Förster, 1869 or Neliopisthus Thomson, 1883 in the tribe Oedemopsini . In addition, Monoblastus from Tryphonini also has a down-curved tip of the ovipositor and sheaths which are weakly medially expanded. As the extant Thymaris have a more slender first tergite and Neliopisthus more strongly expanded ovipositor sheaths than what we see in the fossil, we place the fossil in Monoblastus , to which the fossil also closely resembles in the wing venation. However, we add a question mark behind the genus name as the laterally extended epicnemial carina and longitudinal sculpture on T1 correspond better to Thymaris .

Tryphoninae Shuckard, 1840

Zagryphus Cushman, 1919

Figures

Figure 16. Monoblastus? senilis (Brues, 1910) comb. nov. A. Photograph of the holotype obtained from the MCZ; B. Our interpretative drawing of the fossil. Thicker lines indicate outlines of body structures, thinner lines show characters inside these outlines, and dotted lines represent uncertain interpretations.