Pherhombus parvulus Meier & Wacker & Klopfstein 2022, n. sp.
Creators: name: Meier, Noah
name: Wacker, Anina
name: Klopfstein, Seraina
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Ichneumonidae
Pherhombus
Pherhombus parvulus

description: Pherhombus parvulus n. sp.
Figure 3
Material. Holotype, #10652, part and counterpart; sex unknown. Part and counterpart about equally informative, often showing complementary structures (e.g., first tergite). Collector: Jan Verkleij. Deposited at Fur Museum, Nederby.
Type horizon and locality. The fossil was found in Denmark, MorsØ Kommune, Ejerslev in cement stone which has a geological ageof about 54 Ma (early Eocene).
Etymology. In Latin, “ parvulus ” is the diminutive of “parvus” which means small or tiny. This refers to the fact that the fossil species is only 3.3 mm long, which is about half the size of all other described Pherhombinae.
Diagnosis.
Taxonomic placement. Due to the nearly complete preservation of the forewing venation, this species can be placed within the Ichneumonidae with certainty, whichare distinguished from the related Braconidae by lacking vein 1-Rs+M (sometimes with the exception of a short remain, called ramulus) and by the presence of 2m-cu. The rhombic aerolet is probably the most conspicuous charactervisiblein this fossil; itis onlyshared bymembersof thesubfamilies Mesochorinae and Pherhombinae. Several characters, such as the low number of antennal segments, the forewing 1-M+1-Rs to r-rs ratio, the hindwing 1-Rs to rs-m ratio, and the elongated and parallel-sided first tergite, give evidence for the placement within the monotypic Pherhombinae. Even though the new species was placed with the highest probability as a stem representative, there is currently not sufficient morphological evidence that this species should be placed withina new genus. This placement is supported both by the morphometric and Bayesian phylogenetic analyses (Fig. 1 and 2).
Species diagnosis. This species is very similar both in wing venation and shape of the first tergite to many species of Pherhombus. Nevertheless, it can be easily distinguished from all currently described species by its small size (body length: 3.3 mm, forewing length: 2.9 mm), with all other Pherhombus species ranging in body length from 6.7 to more than 9 mm and forewing length from 4.7 to 9.5 mm (Tolkanitz et al. 2005; Manukyan 2019). It is further distinguished from most other species by the parallel-sided antennal segments, which are otherwise widened towards the apex in all species except perhaps P. kraxtepellensis and P. kasparyani (Manukyan, 2019), whose antennae are widest around the 8th or 9th flagellomere and only slightly expanded apically. The new species can be distinguished from these two by the presence of a distinct ramulus and by the hyaline wings (smoky in P. kasparyani).
Description.
Preservation. Dorsalview. Headonlypartially preserved, antennae nearly complete with partly clear segmentation. Mesosoma not well preserved, hardly any characters visible except possible hind border of mesoscutum; wings stretched out flat, all four wings nearly complete; partial mid and hind legs visible. Metasoma anteriorly almost complete but segmentation posteriorly unclear; posterior part of metasoma ending abruptly or incomplete, genitalia not visible.
Body 3.3 mm; fossil in different shades of brown; strongly sclerotized parts, such as head or first tergite, distinctly darker than rest, wings hyaline.
Head deformed, no detailed structures distinguishable. Antenna slender, with about 20 flagellomeres (+/- 3); scape and pedicel of normal dimensions (as far as visible), first flagellomere almost 7.0 times longer than apically wide.
Mesosoma rather short and stout; triangular dark patches at forewing base probably corresponding to axial sclerites. Forewing 2.9 mm; areolet closed, rhombic, 3r-m with a bulla at posterior end; 4-Rs straight; ramulus present, slightly longer than width of surrounding veins; pterostigma 4.5 x longer than wide; radial cell 3 x longer than wide; 1cu-a meeting M+Cu opposite 1-M&1-RS; 2m-cu nearly straight, somewhat inclivous, probably with a single large bulla in anterior third or half; 3-Cu about 0.75 x as long as 2cu-a. Hindwing 1-Rs 0.47 x as long as rs-m; 2-Rs tubular on entire length (not counting last 10%); 1-Cu clearly shorter than cu-a. Mid leg very slender, both coxa, femur and parts of tibia and tarsus visible. Hind leg with very long coxa, at least 2.1 x longer than wide; both femur and parts of tibia preserved, femur rather elongated, more than 5.0 x longer than wide.
Metasoma appearing somewhat clubshaped, with widest part close to posterior end; tergite 1 slightly more than 4 x longer than wide, narrow and parallel sided; tergite 2 transverse, 0.75 x as long as wide. Posterior metasomal segments appear truncated, lack of ovipositorsuggests a male, but incomplete preservation also possible.
description: Published as part of Meier, Noah, Wacker, Anina & Klopfstein, Seraina, 2022, New fossil wasp species from the earliest Eocene Fur Formation has its closest relatives in late Eocene ambers (Hymenoptera, Ichneumonidae, Pherhombinae), pp. 1-17 in Bulletin of the SSB (8427) (8427) 1 (1) on pages 8-10, DOI: 10.18061/bssb.v1i1.8427, http://zenodo.org/record/6000933