Orthocentrus defossus 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

* Orthocentrus defossus Brues, 1910

Fig. 7

Material.

Photographs of the holotype (part only, #2238) obtained from the MCZ.

Stratum.

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

Description.

Probably female. Holotype in ventro-lateral view with metasoma bent under the body, with nearly complete antennae, head, mesosoma, both fore and one hind wing and nearly complete hind legs. Overlapping metasoma, legs and fore wing make interpretation partially difficult. Hairs on wings and hind legs very well preserved. Body length 8.2 mm.

Black or dark brown on head, mesosoma and T1; dark brown on antennae, base of hind coxa, hind femur and outer side of hind tibia, red on remainder of hind legs and T2 until end of metasoma; wing venation dark brown to orange.

Head with face bulging, eye rather small, malar space very long and with a deep groove. Antennae stout, with at least 20 flagellomeres, scape elongate, 1.8 × as long as wide. Mesosoma short and stout; pronotum with a short lower part of epomia and parallel wrinkles posteriorly, which are mirrored on mesopleuron; epicnemial carina might be present ventrally (or this is the impression of a fore coxa). Metapleuron rather high, with what seems like strong juxacoxal carina visible on both sides; propodeum with pleural and a low apical transvers carina visible, remainder unclear. Wings evenly hairy, fore wing 4.5 mm, with areolet rather large and pentagonal, receiving 2m-cu close to its outer corner, 4M thus very short; 1cu-a meeting 2Cu distinctly after 1M; 3Cu a little shorter than 2cu-a; cell 2R short and stout (2.6 ×). Hind wing with 1Cu almost 4 × longer than 1cu-a, 2Cu rather weak, 1Rs somewhat longer than rs-m. Hind legs rather stout, femur 2.5 × and tibia 4.5 × longer than wide. Metasoma poorly preserved, but last segments seemingly compressed and tergites transversal. Ovipositor sheaths about as long as height of tip of metasoma.

Interpretation.

We agree with the original placement of this species. Despite the difficulties in interpreting the ventral part of the mesosoma and the metasoma, the characters visible on the head and wings allow confidence in placing this species in the Orthocentrus genus-group of Orthocentrinae . Character evidence for this placement are the bulging face, long malar space, and shortened antennae with an elongate scape. Within the group, only Orthocentrus contains species with such a large, pentagonal areolet, and the malar groove and 1cu-a meeting 2Cu distinctly after 1M are a further good match with this genus.

Orthocentrinae Förster, 1869

Orthocentrus ? Gravenhorst, 1829

Figures

Figure 7. Orthocentrus defossus (Brues, 1910) 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