Rhyssa gulliveri Viertler, Klopfstein & Spasojevic sp., 2023

Viertler, Alexandra, Urfer, Karin, Schulz, Georg, Klopfstein, Seraina & Spasojevic, Tamara, 2023, Impact of increasing morphological information by micro-CT scanning on the phylogenetic placement of Darwin wasps (Hymenoptera, Ichneumonidae) in amber, Swiss Journal of Palaeontology (30) 142 (1), pp. 1-27 : 17-19

Rhyssa gulliveri Viertler, Klopfstein & Spasojevic sp. nov. ( Fig. 8 )

urn:lsid:zoobank.org:act:FB7705BB-0A5E-424A-906E-94B76CFBFE40

Etymology: Named after Lemuel Gulliver from Gulliver’s Travels, who was trapped despite his body size.

Type specimen: Holotype: male (NMB F3742). Baltic amber. Location: Kaliningrad region (Yantarny, Russia). Deposited in Switzerland, Natural History Museum in Basel.

Type condition: Well preserved, with only minor milky coatings on the clypeus. Additional spider inclusion and trichomes, probably from oaks.

Systematic placement: The specimen is clearly placed in Rhyssinae due to the distinct transverse rugae on the mesoscutum, dorsally absent occipital carina and the very short 1Cu vein in the hind wing. The chisel-shaped upper tooth (Character #2), the junction of occipital and oral carinae distant from the mandibular base (not coded), the very slender and elongate pterostigma (Character #140), and the presence of a narrow glymma (Character #162), suggest a placement in the genus Rhyssa Gravenhorst, 1829 . Also, the number of flagellomeres (Character #40), the shape of the anterior part of the pronotum with a longitudinal impression forming a channel (Character #47), and the position of the metacoxal cavity (Character #89) agree with Rhyssa . The combined-evidence analysis confirms the placement of the fossil in the extant genus Rhyssa with an attachment frequency of over 97% in the RoguePlot.

Diagnosis: There are three other fossils described in the genus Rhyssa , all of them compression fossils in sediments, and more poorly preserved. Rhyssa antiqua Heer, 1867 differs from Rhyssa gulliveri sp. nov. by having a very large and non-petiolate areolet, a straight 2m-cu and veins 4Cu and 5Cu of similar length. Rhyssa? juvenis Scudder, 1890 is preserved poorly and, according to a recent revision ( Spasojevic et al. 2018), its body parts seem to belong to several insect specimens. In Rhyssa? juvenis the only characteristics matching Rhyssa are the partially visible fore wing venation and the debatable presence of rugae on the mesoscutum. So, comparing its wing venation with Rhyssa gulliveri sp. nov. we find that R.? juvenis has a more elongate and non-petiolate areolet. Rhyssa petiolata Brues, 1906 is described from a female specimen, which has T 6 and T 7 small and triangular, whereas Rhyssa gulliveri sp. nov. is a male and has T 6 and T 7 similar in size as T 4 and T 6. Although the wings of Rhyssa petiolata are poorly preserved, the areolet appears to be open, in contrast to Rhyssa gulliveri sp. nov. and all described extant Rhyssa species (exceptions in some small males ( Townes, 1969a)).

Description: Body 12 mm. Colouration appears dark, either brown or black.

Head. Face separated from clypeus, evenly convex. Mandibles bidentate, not twisted, apex width 0.58 × base width, about 1.5 × longer as base width; teeth appear chisel shaped, upper tooth length seems subequal to lower, width of upper tooth equal or slightly broader than lower. Malar space short, 0.3 × of mandible base width. Maxillary palps with five, labial palps with four segments. Clypeus flat, small, without transverse division, apical margin unclear. Labrum concealed. Apical tentorial pits normal sized. Inner orbits parallel in front view, straight opposite antennal sockets. Eyes without setae, height 0.86 × head height in lateral view. Ocelli normal sized. Genae smooth. Occipital carina present ventrally, appears absent dorsally; junction to hypostomal carina distant from mandibular base by about 0.6 × basal mandible. Vertex evenly rounded down to occipital carina. Antennae 9.3 mm, with 32 segments; more or less even thickness throughout; scape from front view truncated at 40° to longitudinal axis, 1.5 × longer than wide (measured at longest/widest point), clearly larger than pedicle; first antennal segment length 4.2 × apical width; other antennal segment lengths about 1.2–2 × apical width.

Mesosoma. Pronotum rather short, about 0.68 × longer than deep; epomia appears complete; anterior part rather long, triangularly protruding laterally; longitudinally impressed, forming a channel. Mesoscutum with sharp transverse rugae, appears evenly pubescent; notauli short, not reaching mid length of mesoscutum, strongly converging and deeply impressed anteriorly. Scutellum more or less flat, lateral longitudinal carina seems absent. Mesopleuron flat; epicnemical carina curving anterior but seems not to reach anterior margin of mesopleuron; sternaulus absent. Mesopleural furrow more or less straight with a shallow horizontal impression. Mesosternum appears transverse in front of fore coxa, posterior transverse carina of mesosternum absent. Metapleuron 1.4 × longer than deep; submetapleural carina complete, anterior section unmodified; pleural carina present as distinct carina on whole length; juxtacoxal carina absent. Propodeum dorsally flattened, about as long as wide, hind margin simple; lateromedian carina absent; traces of lateral longitudinal carina posteriorly; anterior transverse carina absent; posterior transverse carina absent; spiracle oval, about 2.2 × longer than wide, separated from pleural carina by about its minimum diameter. Metacoxal cavity with dorsal margin above lower margin of metasomal foramen magnum.

Fore legs ventrally unspecialized; tibia without tooth; 4th tarsomere longer than wide. Fore and mid tibia with scattered long and stronger spines. Mid tibia with row of strong spikes on inner side apically; with two spurs, equal in length. Hind coxa 1.76 × longer as wide; femur 4.75– 5.2 × longer than wide, without modification; tibia with two spurs, inner slightly shorter than outer; 1st tarsomere 10.5 × longer than apically wide. Claws appear simple.

Wings. Fore wing 8.7 mm. Areolet closed, strongly petiolate, oblique quadratic shape with 4M very short and 3rs-m similar length as 2Rs; 2m-cu slightly and evenly bowed outwards, with two bullae, that cover 20% of 2m-cu and are evenly distributed; vein 3rs-m with one bulla; 4Cu 1.9 × 5Cu; 4Rs appears sinusoidal; ramulus appears absent; 1cu-a postfurcal to 1M+1Rs with 2Cu 2 × 2Cu width, angle to vein 2Cu clearly smaller than 65°–70°; pterostigma 6.8 × longer than wide, 0.8 × 1 R 1; cell 2 R 1 4.2 × longer than wide; 5M tubular; vein 2Cu 0.92 × 1M + 1Rs, 0.94 × r-rs; cell 2Cu 4.4 × longer than wide; 1m-cu&2Rs+M vein arched; 3Cu similar length than 2cu-a. Hind wing with cu-a 5.3 × 1Cu; veins 2Rs, 2M and 2Cu appear tubular throughout; 1Rs 1.6 × rs-m.

Metasoma. 7.7 mm, depressed to cylindrical. T 1 parallel-sided in dorsal view, 1.8 × as long as posteriorly wide, evenly but weakly rounded throughout whole length in lateral view; glymma present; latero-median carina absent. S1 about 0.5 × T 1. T 1 slightly longer than T 2 dorsally, separated by normal joint. T 2 1.1 × as long as posteriorly wide; latero-median carina absent; laterotergites creased but appear more or less absent. T 3– T 6 subquadrate in dorsal view. T 6 and T 7 similar in size. S7 flat and evenly sclerotized. Apex of aedeagus appears dorsoventrally depressed.

Figures

Fig. 8 Holotype of Rhyssa gulliveri sp. nov. A Habitus of specimen, lateral view. B Rugae dorsally on mesoscutum.C Face, anterior view, partially hidden by spider inclusion and milky coatings. D Face, more laterally with visible mandibles.E First tergite on metasoma, lateral view.F Head and mesoscutum, dorsal view. G Interpretative drawing with an additional drawing of the propodeum and T1 in dorsal view, where photos and micro-CT scan were used as templates.Scale bar A: 2 mm, B and C: 1 mm, D: upper 1 mm, lower 2 mm