Triclistus levii Viertler, Klopfstein & Spasojevic, 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 : 12-14

Triclistus levii Viertler, Klopfstein & Spasojevic sp. nov.

( Fig. 6 )

urn:lsid:zoobank.org:act:8EA74EE3-B59E-474D-8F6A-E6A3A01FAA8A

Etymology: This species is named in honour of A. Viertler’s loyal fur child Levi.

Type specimen: Holotype: male (DO-3441-M). Dominican amber. Location : unknown. Deposited in Germany, Staatliches Museum für Naturkunde in Stuttgart.

Type condition: The amber piece is partially darkened, obscuring parts of the fossil, with a drilled hole, made most likely for transforming the amber piece to jewellery. The surface of this amber piece partially cracked due to an accident and was cast in resin to stabilize it for future studies.

Systematic placement: The following characters confidently place this fossil in Metopiinae : A convex face without clypeal sulcus, a triangular process on the upper face between the antennal segments, stout and short legs, and shortened tarsal segments. With the interantennal high ridge that reaches to the frons, this fossil resembles Colpotrochia , Cubus , and Triclistus Förster, 1869 .

Important characters that support the affinity of the fossil to Triclistus were visible before the scanning and include mandible dimensions (Character #1), number of flagellomeres (Character #40), presence of both lateromedian and lateral longitudinal carinae, and posterior transverse carina on the propodeum (Characters #76 & #79), one stout and one long spur on the hind tibia (Character #111), closed areolet with one bulla (Character #128), distally arched 4Rs (Character #137), several wing ratios (e.g. length ratio of Character #144: 2Cu and 1 M +1Rs and Character #145: 1 M +1Rs and r-rs), and moderately broad dimension of laterotergite 3 (Character #194). This placement is congruent with the results of the phylogenetic placement.

Diagnosis: There are two other fossil Triclistus species described, both from sediments, Triclistus ventrator (Khalaim, 2008) from the Biamo assemblage ( Russia, late Eocene, or Early Oligocene), and Triclistus bibori ( Viertler et al. 2022a) from the Fur formation ( Denmark, Early Eocene).

What stands out in Triclistus levii sp. nov. is the length of the basal antennal segments, which are rather long, especially the first segment, which is 4 × longer than posteriorly wide. This was also observed in T. ventrator . Nevertheless, T. levii sp. nov. differs from T. ventrator in having a straight 2m-cu vein with only one bulla. Other characters are difficult to compare since T. ventrator is more poorly preserved. T. bibori is generally much larger than T. levii sp. nov. and has much stouter antennal segments and T 1. While T. levii sp. nov. has either none or very weak and short latero-median carina on T 1, T. bibori shows a prominent latero-median carina that exceed half the length of T 1.

Description: Body 5.6 mm. Head, antenna, mesosoma and metasoma seem dark brown or black. Legs appear bright, yellow, or orange.

Head. Face not separated from clypeus, evenly convex to slightly inflated. Mandibles bidentate, length 1.5–2 × base width, apex width 0.4–0.5× base width, not twisted. Malar space short, 0.35 × mandible base width, without modifications. Maxillary palps with five segments, labial palps with four segments. Clypeus flat, without transverse division, apical margin appears simple. Labrum concealed. Apical tentorial pits small. Upper face with triangular process. Inner orbit appears parallel in frontal view, weakly concave opposite antennal sockets. Eyes without setae, height 0.88 × head height in lateral view. Ocelli seem normal-sized. Genae smooth. Occipital carina complete. Vertex precipitously declivous behind posterior ocelli, flat to concave. Antennae 4.5 mm, with 23–24 segments; scape length 1.2 × width, laterally 1.1–1.2 × pedicle length; first antennal segment length 4.3 × apical width; other antennal segment lengths about 2.8 × apical width. Frons with high lamella between antennal sockets, almost reaching median ocellus.

Mesosoma. Pronotum moderately long, about same length as depth, upper posterior corner overhanging sclerite partially or completely; epomia appears absent. Mesoscutum evenly pubescent, finely punctate, carina along lateral margin seems complete; notaulus short, present only on frontal vertical part, shallow. Scutellum more or less flat, with lateral longitudinal carina absent. Mesopleuron strongly convex antero-dorsally; epicnemical carina extends to subtegular ridge; mesopleural furrow more or less straight with isolated puncture; sternaulus absent, posterior ventral corner with a lobe. Mesosternum appears transverse in front of fore coxa, posterior transverse carina absent in front of mid coxa, but with two small lobes protruding on inner side in front of mid coxa. Metapleuron about as long as wide; submetapleural carina complete, anterior section modified into broad lobe; pleural carina present as distinct carina on whole length; juxtacoxal carina absent. Propodeum rounded laterally, about as long as wide; smooth or with weak punctures; hind margin simple; lateromedian and lateral longitudinal carinae present; anterior transverse carina absent, without modifications at junction of lateral longitudinal and posterior transverse carina; posterior transverse carina complete; spiracle separated from pleural carina by less than minimum diameter.

Fore legs ventrally unspecialized; tibia without tooth; 4th tarsomere about as wide as long. Fore and mid trochantellus appear fused with trochanters. Mid tibia with two spurs, inner spur longer than outer. Hind coxa slightly longer than deep; femur 2.4 × longer than wide, without modification; two tibial spurs, inner slender and about 3 ×as long as outer; 1st tarsomere 5.6 × longer than apically wide. Claws appear simple; orbicula seems slender, more than 3.5 × as long as wide.

Wings. Fore wing 3.9 mm, stalked areolet, closed, quadratic shape, with 4M very short and 3rs-m similar length as 2 + 3M; 2m-cu straight with one bulla anteriorly, which covers 40% of 2m-cu; 4Cu and 5Cu equal in length; 4Rs distally arched; 1m-cu&2Rs + M vein evenly arched, with ramulus absent; 1cu-a strongly postfurcal to 1M + 1Rs with 1Cu 3.5 × 2Cu width, angle to vein 2Cu clearly smaller than 65–70°; pterostigma 2.7 × longer than wide; 2 R 1 3 × longer as wide; 5M tubular through the whole length; 2Cu 0.64 × 1M + 1Rs, 1.16 × r-rs; 3Cu longer than 2cu-a. Hind wing with M + CU curved around middle or curved along entire length; 1Cu slightly longer than cu-a; 2Rs and 2Cu veins partly spectral; vein 2M completely spectral; 1Rs about 1.6 × rs-m; eight distal hamuli.

Metasoma. 3.2 mm, depressed. T 1 slightly tapering anteriorly in dorsal view, 1.5–1.6 × as long as posteriorly wide, shape laterally evenly but weakly rounded throughout whole length, but narrower anteriorly; spiracle in anterior half, dorso-lateral carina more or less complete, above or at spiracle; glymma present, rather shallow; laterotergite 1 absent. S1 short, about 0.3–0.4 × length of T 1. T 1 and T 2 separated by normal joint. T 2 without latero-median carina, sculpture either smooth, evenly shagreened, or finely punctured; laterotergite creased, about 0.2 × as long as wide. T 2– T 5 similar in size and dimension, about as long as posteriorly wide. T 3 with laterotergite creased, 0.43 × as wide as long. T 7 seems flat and evenly sclerotized, 0.67 × length of T 6. Parameres 2 × as long as wide at mid length.

Figures

Fig. 6 Holotype of Triclistus levii sp.nov. A Partial fore wing. B Metasoma, posterior end with the parameres. C Habitus of specimen, lateral view. D Head and mesoscutum, dorsal view. E Head. F 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 bars A: 1 mm, B: 0.5 mm C: 1 mm F: bottom 1 mm, top right 0.5 mm