Polysphincta? inundata Brues, 1910

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

Polysphincta? inundata Brues, 1910

Fig. 14

* Polysphincta inundata Brues, 1910

Material.

Photographs of the holotype (part only, #PALE-2135) obtained from the MCZ.

Stratum.

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

Description.

Female. Holotype in lateroventral view, with one nearly complete and one partial antenna, head, mesosoma showing some carinae and sculpture, nearly complete fore wings and one partial hind wing, hind legs strongly and mid and fore legs weakly outlined, metasoma complete with ovipositor with sheaths. Body length 10.1 mm.

Black or dark brown on head, mesosoma and T1, antennae and remaining metasoma orange, hind legs dark brown at least on femur and apex of hind tibia, other legs probably orange.

Head rather short, poorly preserved but outline of eyes partially indicated. Antennae 7.1 mm, with more than 39 (probably around 43) flagellomeres, basal segments longer than wide, from about mid length transverse, scape short. Mesosoma rather stout, with epomia present on pronotum; mesopleuron with epicnemial carina curved forward around mid-height of pronotum, with fine longitudinal carinulae at least in front of mesepimeron. Propodeum with pleural, lateral and lateromedian longitudinal carinae seemingly complete, with indication of low posterior transverse carina and maybe also part of anterior transverse carina. Fore wing 6.8 mm; areolet open, vein 2 + 3M twice as long as 2Rs; 1cu-a meeting 2Cu at the same position as 1M; cell 2R1 rather long, 3.6 × as long as wide. Hind wing with vein 1Rs much longer than rs-m; 1Cu about as long as cu-a (but a bit difficult to see). Legs rather stout; hind femur 3.0 × and hind tibia 7 × as long as wide. Metasoma mostly dorsoventrally depressed and somewhat compressed towards apex, with T1 a bit elongate and nearly parallel sided, with what are probably latero-median and dorso-lateral carinae; T2 and following tergites transverse. Ovipositor 3.8 mm, 1.6 × as long as hind tibia, upcurved at apex, seemingly tapering from about middle to apex; ovipositor sheaths parallel-sided.

Interpretation.

Members of the Polysphincta group of genera are koinobiont ectoparasitoids of spiders and have a unique ovipositor, which is expanded at the base and again around mid-length, from where it evenly tapers into a narrow point. The state of the ovipositor in P. inundata seems consistent with this description, but this is somewhat unclear, despite the in general very good preservation of this fossil. Alternatively, if our interpretation of the ovipositor is wrong and there is not a median swelling, it would point to Clistopyga Gravenhorst, 1829, a sister genus of the polysphinctines. The fact that we cannot see any paired swellings, impressions or raised areas on tergites, which are typical for many but not all polysphinctines, speaks also more for Clistopyga . However, the propodeal carination never occurs in Clistopyga , and although it is reduced in most extant members of the polysphinctines, with at most longitudinal carinae present, the posterior transverse carina occurs in some genera, e.g., Sinarachna Townes, 1960, Acrodactyla Haliday, 1838 and Zatypota Förster, 1869. These genera, however, have shorter ovipositors without the upcurved tip. Because we cannot find a convincing alternative placement for the fossil, we leave it in the current genus but express uncertainty in its placement.

Lycorininae ? Cushman & Rohwer, 1920

Lycorina ? Holmgren, 1859

Figures

Figure 14. Polysphincta? inundata (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.