Lithoserix williamsi Brown, 1986

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

* Lithoserix williamsi Brown, 1986

Fig. 12

Material.

Photograph examined of the holotype (part, # UCM31179 ), obtained from the UCM .

Stratum.

Old Scudder Pit, Florissant shales, Colorado, USA. Late Eocene (Chadronian), 37.2-33.9 My.

Description.

Female. Part showing dorsal view including partially preserved antennae, partial head, mesosoma preservation rather patchy, with right fore wing partial and complete left fore and hind wings, partial mid and hind legs, and metasoma including ovipositor sheaths and ovipositor except tip. Body length 22 mm.

Brown, wing veins dark brown where colour is preserved, femora and posterior half of tergites darker brown, posterior half of tergites possibly darker than anterior.

Head, with complete occipital carina straight to evenly rounded or slightly dipped medially. Antenna e at least 14 mm long, first few segments probably short, only slightly longer than wide. Mesosoma with notauli strongly impressed, converging and extending past half of mesoscutum; scutellum borders unclear, might be displaced posteriorly and visible as small triangular structure or larger and broken around middle; metanotum visible, of regular size. Propodeum with carinae difficult to interpret, but at least with complete lateral longitudinal carinae, anterior portion of median longitudinal carinae, anterior transverse carina and some indication of pleural carinae; spiracle small and oval. Fore wing 16.5 mm, with areolet almost triangular, 2 + 3M longer than 4M; 4Rs clearly bowed at base; 1cu-a meeting M + Cu opposite of 1M, 3Cu slightly longer than 2cu-a; ramulus longer than twice the width of the surrounding veins; cell 2R1 4.3 × longer than wide. Hind wing with 1Rs longer than rs-m and 1Cu clearly shorter than cu-a. Legs rather stout, hind femur around 3.4 × longer than wide. Metasoma with T1 quadrate, only slightly narrowed towards base, with dorsal longitudinal carinae parallel to each other and almost reaching or reaching posterior margin of tergite; T2 subquadrate with oblique grooves cutting off anterolateral corners; T3-T7 transverse. Ovipositor at least 19 mm long, at least 3.5 × as long as hind tibia, straight and parallel sided, rather robust.

Interpretation.

Described originally in the symphytan family Siricidae , this taxon was moved to the tribe Ephialtini in Pimplinae more recently (Kasparyan and Rasnitsyn 1992). It clearly belongs to Ichneumonidae based on the wing venation. A quadrate areolet and 2m-cu evenly curved outwards, with two bullae, quadrate T1 with lateromedian longitudinal carinae and long ovipositor, clearly support the placement of the genus in Pimplinae . Tribal placement is in fact not unequivocal, as some Delomeristini genera also show as much resemblance to Lithoserix as the ephialtine Dolichomitus Smith, 1877 mentioned by Kasparyan and Rasnitsyn (1992). The presence of a transverse carina in the anterior part of the propodeum is unusual for Pimplinae and can be seen only in Xanthopimpla Saussure, 1892 ( Pimplini ) some Theroniini and, in a very reduced form, in Delomerista Förster, 1869 ( Delomeristini ), In fact, the presence of rather extensive carination on the propodeum is rather reminiscent of Delomeristini , although this is probably the plesiomorphic state in the subfamily ( Kopylov et al. 2018). To distinguish between Delomeristini and Ephialtini , the tarsal claws would need to be examined, which are not preserved in either of the two specimens currently attributed to the genus. In any case, the long ramulus and short flagellar segments are unique for Lithoserix , which we suggest to keep without tribal assignment in Pimplinae .

Pimplinae ? Wesmael, 1845

Pimpla ? Fabricius, 1804

Figures

Figure 12. Lithoserix williamsi (Brown, 1986) comb. nov. A. Photograph of the holotype obtained from the UCM; 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.