Lithoserix antiquus (Saussure, 1852) Spasojevic & Broad & Klopfstein, 2022

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 antiquus (Saussure, 1852) comb. nov.

Fig. 11

* Pimpla antiqua Saussure, 1852

(Pimpla antiquus Saussure according to Theobald, 1937)

Material.

Specimen databased as ‘holotype’ (part and counterpart, Am 21 / # MNHN.F. B24391 -1 and Am 21 2 / # MNHN.F. B24391 -2) examined (but see notes under Interpretation) at MNHN.F, from where its photographs were also obtained .

Stratum.

Aix-en-Provence, Bouche-du-Rhône, France. Late Oligocene (Chattian), 28.4-23.0 Ma.

Description.

Female. Part showing dorsal view with almost complete antennae, partial head, mesosoma with both fore and hind wings, partial mid and hind legs, and metasoma including detailed sculpture and ovipositor sheaths except tip. Counterpart with negative impression of wings, ventral aspect of mesosoma, while metasoma shows a mix of a ventral aspect and what we interpreted as the inner sides of the tergites, where the sternites were weakly sclerotized, ovipositor sheaths complete. Body length 15.2 mm.

Brown, wing veins dark brown where colour is preserved, legs and hind margins of tergites orange.

Head only partially preserved, rather short; Antenna e at least 13.7 mm, segment boundaries not discernible. Mesosoma preservation patchy; notauli present on about basal third; scutellum rather short, might be bounded by carinae; axilliary trough with transverse wrinkles; metanotum short. Propodeum with pleural carina and at least lateral longitudinal carinae complete, anterior transverse carinae probably present, remainder unclear. Fore wing 13.9 mm, with areolet almost triangular with outer vein longer than inner vein, 4Rs a little bowed at base and apex; 1cu-a meeting M + Cu opposite of 1M, 3Cu about as long as 2cu-a; ramulus longer than twice the width of the surrounding veins; cell 2R1 4.6 × longer than wide. Hind wing with 1Rs longer than rs-m and 1Cu clearly shorter than cu-a. Legs rather stout, hind femur 3.5 × longer than wide. Metasoma with T1 quadrate, only slightly narrowed towards base, with dorsal longitudinal carinae distinct on basal half and far away from each other, with parallel carinulae and some punctures along outer margins and towards lateromedian transverse impressions in posterior half; T2-T7 transverse, with a band along hind margin smooth, remainder strongly and densely punctate; T2 with oblique grooves cutting off anterolateral corners, maybe with thyridiae sunken. Ovipositor 4.7 mm, 0.5 × as long as metasoma, straight and parallel sided, rather robust.

Interpretation.

The specimen covered here was described by Theobald (1937), who stated that it was close but not identical to the holotype described by Saussure (1852), and that he could not find the latter. The drawing in the original description (plate 23, fig. 5 in Saussure 1852) indeed shows a different outline of the rock where the fossil is placed in, and Theobald mentions several differences especially in the wing venation. However, there are multiple lines of evidence that the present specimen might indeed represent the holotype, most of all the remarkable similarity of the positioning of the body of the specimen, including the exact angle between the antennae and positions of the legs. We thus suspect that this is indeed the holotype of P. antiqua , and that either Saussure took the artistic liberty to draw a more generous outline of the rock, or it was trimmed to a smaller size later on.

The species was transferred to Braconidae by Aubert (1967) without any comment, and thus listed as "Species incertae sedis", in the world catalogue ( Yu et al. 2012). It clearly belongs to the family Ichneumonidae , given the venation in fore and hind wings, and to the subfamily Pimplinae given the triangular areolet, hind wing 1Cu shorter than cu-a, quadrate T1, long ovipositor, and sculpture of the metasoma. The carinae on the propodeum, long ramulus and broad smooth bands apically on the tergites preclude a placement in the genus Pimpla as it is defined today (Gauld et al. 2002). However, in all the afore-mentioned characters, it is very similar to the only species placed in the Eocene genus Lithoserix Brown, L. williamsi (Brown 1986) from the Florissant formation. We thus transfer it to this genus; see there for details on the differences to other genera. Lithoserix antiquus can be distinguished from L. williamsi by the much shorter ovipositor, shorter mesoscutum and the dorsal carinae on T1 extending to less than the mid-length of the tergite.

Pimplinae Wesmael, 1845

Lithoserix Brown, 1986

Figures

Figure 11. Lithoserix antiquus (Saussure, 1852) comb. nov. A. Photograph of the holotype obtained from MNHN. F; B. Our interpretative drawing of the fossil. Thicker lines indicate outlines of body structures, thinner lines show characters inside these outlines, dotted lines represent uncertain interpretations and grey surface indicates sculpture of the cuticle. Grey areas show conspicuous sculpture of the cuticle.