The fossils were embedded in small clear pieces of amber. They have been prepared using a diamond disk, examined using a Nikon binocular microscope SMZ 1500. Photographs have been taken with an Amscope camera MU900, and the images treated with Adobe Photoshop Element 12.

The nomenclature and classification follow Azevedo et al. (2018). Main measurements and indices used are as follow: length of forewing (LFW); length of head (LH); width of head (WH); width of frons (WF); height of eye (HE); ocello-ocular line (OOL); width of ocellar triangle (WOT); diameter of anterior ocellus (DAO); vertex-ocular line (VOL). The nomenclature of integument sculpture follows Harris (1979).

Class: Insecta Linnaeus, 1758

Order: Hymenoptera Linnaeus, 1758

Family: Bethylidae Haliday, 1840

Subfamily Scleroderminae Kieffer, 1914

Genus Paleoscleroderma gen. n.

Type species. Paleoscleroderma lamarrei sp. n.

Etymology. Named after the genus Scleroderma and ‘paleo’ for ancient.

Diagnosis. Male characters only. Antenna with 11 flagellomeres; body not depressed; eye distinctly shorter than head in lateral view; mandible with five teeth; occipital carina absent; well-developed notauli; metapectal–propodeal complex strongly sculptured with carinae; mesoscuto-mesoscutellar suture partially closed but with two lateral foveae; transepisternal fovea absent; poststigmal abscissa of radial 1 very short; metasomal segment II 1.5 as long as segment III.

Paleoscleroderma lamarrei sp. n.

(Fig. 1, Fig. 2 and Fig. 3)

Etymology. Named after Mr. Lamarre Gauthier, husband of the first author.

Locus typicus and stratum typicum. Le Quesnoy, Chevrière, region of Creil, Oise department, France; lowermost Eocene, Sparnacian, level MP7 of the mammal fauna of Dormaal.

Holotype. MNHN.F.A70917 (PA 8508), male, stored in the collections of the “Muséum national d’histoire naturelle”, Paris, France.

Main measurements. Body ca. 2.5 mm long; WH 0.44 mm; LH 0.35 mm; HE 0.062 mm; WF 1.137 × HE; OOL 0.148 × WOT.

Description. Male; body 2.01 mm long, not depressed, not strongly foveolate; LFW 1.37 mm; head black; metasoma black and castaneous, legs castaneous, antenna castaneous; wings hyaline; head and thorax ‘setose’.

Head. Mandible with five apical teeth, lowermost tooth of mandible triangular, not directed inward; four visible maxillary palpomeres (probably five), two or three labial palpomeres hardly visible; clypeus hardly visible; antenna with 11 flagellomeres; scape: 0.126 mm long × 0.044 mm wide, pedicel: 0.066 × 0.038 mm, F1: 0.027 × 0.033 mm, F2: 0.038 × 0.033 mm, F3: 0.038 × 0.033 mm, F4: 0.033 × 0.033 mm, F5: 0.055 × 0.033 mm, F6 and F7 not visible, F8: 0.027 × 0.033 mm, F9: 0.027 × 0.033 mm, F10: 0.022 × 0.033 mm, F11: 0.033 × 0.0033 mm; eyes pubescent; frons coriaceous with median depression; occipital carina absent; WH 0.44 mm; LH 0.35 mm; HE 0.062 mm; WF 1.137; OOL 0.148; ocellar triangle equilateral.

Mesosoma: thoracic dorsum weakly coriaceous covered with setae; pronotal disc with anterior transverse carina weak, dorsal pronotal area elongate, longer than anteromesoscutum; dorsal pronotal area without elevation wider anteriorly; metanotum neither developed medially nor overlapping mesoscutellum posteriorly; mesoscuto-mesoscutellar suture not complete, opened in its median part, but with two lateral foveae linked to suture by line; well-developed notauli; parapsidal signum almost complete; mesopleuron without any transepisternal line on mesopleuron; strongly sculptured metapectal–propodeal complex with carinae, but not depressed medially, without posterior spines, as broad as long, with distinct lateral carinae, and posterior carina very weak medially.

Wings covered with short setae and bordered with small setae; forewing with anterior border angularly incurved anterior to pterostigma; costal vein absent; vein 2r-rs&Rs vein long and as strong as other veins; cells R and 1Cu closed; first medial cell absent; no basal stub of Rs + M; poststigmal abscissa of R1 very short, distal ghost veins present (Azevedo et al., 2018 and Terayama, 2006: 14).

Metasoma: short petiole; six tergites, convex, partly covering sternites; posterolateral margin of tergite II not strongly concave, without pair of spots, pits or depressions; tergites III and IV with concave part in middle; genitalia and subgenital structures hardly or not visible.

Tergites length × height: T1: 0.173 × 0.237 mm, T2: 0.181 × 0.395 mm, T3: 0.126 × 0.418 mm, T4: 0.102 × 0.363 mm, T5: 0.086 × 0.316 mm, T6: 0.11 × 0.181 mm.

Remarks. This fossil differs from Eupsenella eocenica in its more reduced venation (De Ploëg and Nel, 2004). It differs from Epyris moulyi in the shape of the head, the ornamentation of the metapectal–propodeal complex, etc. It differs from Chlorepyris gallicus in the shape of the pronotum, and from Elektroepyris magnificus in the shape of the eyes and head, and the very reduced poststigmal abscissa of radial 1 (Perrichot and Nel, 2008). Thus it corresponds to a new species.

After the key to subfamilies of Azevedo et al. (2018), this fossil would fall in the Scleroderminae because of the following characters: winged forms (macropterous); forewing with Rs + M vein absent; metanotum neither developed medially nor overlapping mesoscutellum posteriorly; metapectal–propodeal complex not depressed medially, without posterior spines; body not strongly foveolate; metasomal segment II much less than twice as long as subsequent ones; mesopleuron without transepisternal line; forewing with anterior border angularly incurved anterior to pterostigma; costal vein absent; occipital carina absent, occiput rounded.

More precisely, the metasomal segment II of Paleoscleroderma gen. n. is 1.5 as long as segment III, while it is twice or more as long as III in the Mesitiinae (Argaman, 2003). There is a transepisternal line on the mesopleuron of the Mesitiinae and Epyrinae, unlike in Paleoscleroderma (Argaman, 2003 and Azevedo et al., 2018).

After the key to sclerodermine genera of Azevedo et al. (2018), Paleoscleroderma would fall near Glenosema Kieffer, 1905 for the following combination of characters: antenna with 11 flagellomeres; body not depressed; eye distinctly shorter than head in lateral view; mandible with five teeth. Paleoscleroderma strongly differs from Glenosema in the well-developed notauli and the strongly sculptured metapectal–propodeal complex with carinae.

The ornamentation of the metapectal–propodeal complex of Paleoscleroderma more strongly resembles those of Chilepyris Evans, 1964 (which has no notauli and mandible with three teeth), Discleroderma Kieffer, 1904 (which has notauli even if less pronounced than in Paleoscleroderma, and mandible with four apical teeth), and Nothepyris Evans, 1973 (with pronounced notauli, but mandible with two teeth). In Paleoscleroderma, the mesoscuto-mesoscutellar suture is partially closed, unlike in these genera.

Fossil Scleroderminae are quite rare, with only the Late Cretaceous genus Celonophamia Evans, 1973, with two species C. taimyria Evans, 1973 and C. granama McKellar and Engel, 2014, the extant genus Sclerodermus Latreille, 1809 with the species S. quadridentatus (Cockerell, 1917) (original spelling Scleroderma (?) quadridentatus) from the Cretaceous Burmese amber, and the extant genus Plastanoxus Kieffer, 1904 with the species P. atrescens Sorg, 1988 from Baltic amber.

P. atrescens differs from Paleoscleroderma in a more reduced wing venation and presence of only four mandibular teeth (Sorg, 1988). S. quadridentatus differs from Paleoscleroderma in the very long pronotum (Cockerell, 1917). C. taimyria Evans, 1973 and C. granama have a very short pronotum, unlike Paleoscleroderma (Evans, 1973 and McKellar and Engel, 2014).

Subfamily: Pristocerinae Mocsáry, 1881

Genus Pristocera Klug, 1808

Pristocera alaini sp. n.

(Fig. 4 and Fig. 5)

Etymology. Named after Mr. Alain Falières, father of first author.

Locus typicus and stratum typicum. Le Quesnoy, Chevrière, region of Creil, Oise department, France; lowermost Eocene, Sparnacian, level MP7 of the mammal fauna of Dormaal.

Holotype. MNHN.F.A70916 (PA 3389), male, stored in the collections of the “Muséum national d’histoire naturelle”, Paris, France.

Diagnosis. Antenna long, reaching the level of mid part of metapectal–propodeal complex; a strong vein cu-a; antennomeres basally narrowed; frons setose; wings hyaline.

Description.

Male; body 1.72 mm long, not depressed, not strongly foveolate; LFW 0.714 mm (preserved part); head black; gaster castaneous lightly iridescent, legs castaneous, antenna castaneous; wings hyaline.

Head smooth, not roughly sculptured; mandible with three apical teeth; five visible maxillary palpomeres, two or three hardly visible labial palpomeres; no spine on gena; medial clypeal lobe trapezoidal with apical margin slightly incurved; antenna rather long, reaching mid part of metapectal–propodeal complex; 11 flagellomeres, cylindrical but basally narrowed; scape: 0.031 mm long × 0.026 mm wide, pedicel: 0.073 × 0.021 mm, F1: 0.052 × 0.021 mm, F2: 0.052 × 0.021 mm, F3: 0.052 × 0.026 mm, F4: 0.052 × 0.026 mm, F5: 0.052 × 0.031 mm, F6: 0.052 × 0.031 mm, F7: 0,052 × 0.031 mm, F8: 0.052 × 0.026 mm, F9: 0.052 × 0.026 mm, F10: 0.052 × 0.026 mm, F11: 0.068 × 0.0021 mm; frons with numerous setae disposed in several parallel longitudinal lines; ventral part of occipital carina present, but dorsal part hidden; eyes glabrous; WH 0.32 mm; LH 0.32 mm; WF 0.15; OOL 0.14; ocellar triangle equilateral.

Mesosoma: dorsum smooth, not roughly sculptured; pronotum with anterior margin of disc carinate; pronotal declivity accentuated; propleuron junction region elevated triangularly and extending to prosternum; notauli present with internal region weakly foveolate; parapsidal signum strongly reduced; mesoscuto-mesoscutellar suture opened in its median part, with two lateral foveae, each linked to the suture by a thin line; metanotum with medium region narrower than lateral regions, developed medially and overlapping mesoscutellum posteriorly; metanotal groove with six foveae; metapectal–propodeal complex smooth without carinae and posterior spines.

Forewing covered with punctuation and bordered with small setae; anterior border not angularly incurved anterior to pterostigma; costal vein present; vein 2r-rs&Rs vein long and as strong as other veins but with apex destroyed; strong vein cu-a; cells R and 1Cu closed; discoidal cell absent; no basal stub of Rs + M; poststigmal abscissa of R1 short, ghost FRR and SMC veins present.

Metasoma: short petiole; six tergites, convex, partly covering sternites; posterolateral margin of tergite II not strongly concave, without a pair of spots, pits or depressions; tergites III and IV without concave part in middle; hypopygium medially divided into two parts or strongly concave with two very deep lobes (extreme base of hypopygium not visible).

Tergites length: T1 0.115 mm, T2 0.94 mm, T3 0.94 mm, T4 0.073 mm, T5 0.073 mm, T6 0.136 mm.

Remarks. Following the key to subfamilies of Azevedo et al. (2018), Pristocera alaini sp. n. falls in the Pristocerinae because of the following characters: fully winged; forewing with Rs + M vein absent; metanotum developed medially and overlapping mesoscutellum posteriorly. After the key to pristocerine genera, it would fall in the genera Pristocera Klug, 1808 because of the hypopygium medially divided into two parts (main synapomorphy of the genus after Zamprogno and Azevedo, 2014), or strongly concave with two deep lobes as in Propristocera Keffer, 1905. The impossibility to dissect the hypopygium renders difficult to choose between the two situations (see Zamprogno and Azevedo, 2014; figs. 33, 35–36, 40).

Pristocera alaini would fall in Pristocera rather than Propristocera because of the clypeus rectangular with apical margin slightly incurved instead of having a median clypeal lobe projected and angulate (after the diagnoses of the two genera in Azevedo et al., 2018). The extant species of Pristocera have short antennae, reaching at most the distal part of mesonotum, while in Pristocera alaini they can reach the mid part of the metapectal–propodeal complex. Pristocera alaini has the following diagnostic characters of Pristocera: pronotum with anterior margin of disc carinate; pronotal declivity accentuated; propleuron junction region elevated triangularly and extending to prosternum; notaulus present with internal region weakly foveolate; metanotum with medium region narrower than lateral regions; metanotal groove with six foveae. Thus, we attribute this new fossil to the genus Pristocera, but because of the impossibility to examine the internal structure of the hypopigium, this attribution remains somewhat hypothetical.

Pristocera is a genus that comprises 133 valid species distributed in the Afrotropical, Palaearctic, and Oriental regions, including Pristocera skwarrae (Brues, 1933) from the Eocene Baltic amber. Because of the lack of information on the genital structures, it is not possible to compare Pristocera alaini to these taxa. Pristocera alaini shares with Pristocera skwarrae [originally in the fossil genus Parapristocera Brues, 1933, synonymized with Pristocera by Alencar (2017), Alencar et al. (2018), and Azevedo et al. (2018)], the following characters: head and thorax smooth; antennae of similar lengths, with antennomeres cylindrical, but Pristocera alaini has a strong vein cu-a (‘nervulus’ sensu Brues, 1933), the antennomeres basally narrowed, a frons setose, and hyaline wings, unlike P. skwarrae.

Remark. Protisobrachium oligocenicum Théobald, 1937 (Middle Oligocene, Céreste, France) is a Hymenoptera incertae sedis based on a poorly preserved compression fossil (Théobald, 1937).

Two new bethylide wasps, one Scleroderminae Paleoscleroderma lamarrei gen. et sp. n. and one Pristocerinae Pristocera alaini sp. n. are described from the lowermost Eocene amber of Oise (France). Together with the Bethylinae and the three Epyrinae already described from the Oise amber, these new bethylid wasps show that this family was already very diverse during the Lower Paleogene. Further specimens identified as Bethylidae, but different from those already known, remain to be described.