Leptoomus Gibson, 2008

Gibson, Gary A. P. & Fusu, Lucian, 2023, Leptoomidae, a new family of Eocene fossil Chalcidoidea (Hymenoptera), and family classification of Eocene fossil genera originally described in Neanastatinae (Eupelmidae), Zootaxa 5318 (2), pp. 195-216 : 206-209

Leptoomus Gibson

( Figs 1B , 2C‒E, G, H , 3A‒C )

Leptoomus Gibson, 2008: 2‒9 ; Simutnik et al., 2020: 139‒141.

Included species. Leptoomus janzeni .

Diagnosis. Head and mesosoma superficially non-metallic or with metallic green luster under some angles of light ( Simutnik et al. 2020, figs 1C, D). Head with inner margin of eyes distinctly divergent ventrally ( Fig. 2G ); occipital carina absent ( Fig. 2H ). Mandible bidentate, with ventral angulation and slightly concave dorsal truncation. Antenna with dorsal margin of torulus about in line with lower margin of eyes so ventral margin of torulus distinctly ventral to eye ( Fig. 2G ); 12-segmented (1:1:7:3) with 7 subquadrate to transverse, apically widened funiculars and with mps on at least fu 3 ‒fu 7 ( Fig. 3C ; Simutnik et al. 2020, figs 1E, F) and clava; clava compact-ovoid, only about 1.3× as long as wide, and with ventral surface of apical clavomere consisting of large micropilose sensory region ( Fig. 2G ; Simutnik et al. 2020, fig. 1E) (the more extensive sensory region in Fig. 3B : msr apparently an artefact of preservation). Mesoscutellar-axillar complex with axilla transverse-triangular ( Fig. 2H ; Gibson 2008, figs 1, 2, 4, 6‒8), with anterior margin slightly overlapped by posterior margin of mesoscutum when mesonotum not flexed such that inner angles of axillae slightly separated ( Gibson 2008, figs 1, 4, 7: arrows), but when mesonotum flexed inner angles of axllae abutting ( Gibson 2008, fig. 8: arrow); mesoscutellum without apical rim ( Gibson 2008, figs 6‒8). Prepectus slightly convex ( Fig. 2H : pre; Gibson 2008, figs 4, 6). Acropleuron enlarged posteriorly to metapleuron and posteroventrally to ventrolateral level of mesocoxa; acropleural sulcus sulcate and directed horizontally toward posteroventral angle of prepectus where it abruptly recurves dorsally to intersect posterior margin of prepectus in ventral half (because of the abrupt curvature the sulcus differentiates a small, subtriangular mesepisternal region between the prepectus and acropleuron and a slender mesepisternal region ventral to the acropleural suture) ( Fig. 1B; Simutnik et al. 2020, fig. 2A). Mesopectus in ventral or ventrolateral ( Fig. 2C ) view with posterior margin abutting base of mesocoxa, but in posterolateral ( Fig. 2E ) to posteroventral ( Fig. 2D ) view with membranous region visible on either side of inflected mesotrochantinal plate anterior to mesocoxa. Fore wing disc with bare band apical to basal fold contiguous with parastigma ( Gibson 2008, fig. 16; Simutnik et al. 2020, fig. 1H); parastigma separated from base of marginal vein by hyaline break ( Gibson 2008, fig. 16; Simutnik et al. 2020, fig. 1H). Protibia with, possibly articulated, dorsoapical spicule ( Gibson 2008, fig. 21); mesotibia apically with strong spines or pegs in one or two irregular rows ( Gibson 2008, figs 18, 19, inset).

Remarks. The extended diagnosis given above for L. janzeni is to supplement the description in Gibson (2008) because of the discovery of two more fossils belonging to the genus, and to have a more comparative description with Neanaperiallus . Gibson (2008) did not mention flagellar mps for L. janzeni . Simutnik et al. (2020) described mps on fu 3 ‒fu 7 and the apical two clavomeres, but the ventral view of the clava clearly shows mps on the basal two clavomeres and a large micropilose sensory region forming most of the ventral surface of the apical clavomere ( Fig. 2G: cl 3; Simutnik et al. 2020, fig. 1E). A thin apical clavomere (cl 3) is clearly visible only in dorsal view ( Fig. 3B : cl 3; Simutnik et al. 2020, fig. 1F). Simutnik et al. (2020, fig. 2A) also shows the prepectus laterally abutting the incurved posterolateral margin of the pronotum ventral to the mesothoracic spiracle and dorsally overlapping the side of the mesoscutal lateral lobe posterior to the spiracle; the same arrangement also appears evident for the newly discovered female ( Fig. 3A ). Unfortunately, no clear dorsal images for the inclusions confirm the prepectus to have a definite thickness, however it is definitely slightly convex rather than a thin, flat sclerite. The apparent thickness in some inclusions ( Fig. 2H : prepectus) is just one more artefact of preservation.

Figures

FIGURE 1. Lateral view of mesosoma: A, Neanaperiallus masneri; B, Leptoomus janzeni; C, Tanaostigmodes sp.; D, Cynipencyrtus ishii; E, Eopelma gibsoni; F, Savzdargia sp.; G, Neanastatus sp.; H, Lambdobregma sp.; I, Brevivulva electroma. Insets in H and I are dorsal views of apex of mesoscutellum to propodeum; green arrows on images indicate the intersection of base of tegula with dorsal margin of prepectus, white arrows indicate posterior margin of prepectus; see ‘Material and methods’ for abbreviations.

FIGURE 2. A, Cynipencyrtus ishii, mesosoma, ventrolateral view. B, Neanaperiallus masneri, mesosoma, ventral view. C‒E, Leptoomus janzeni: C, mesosoma, ventrolateral view; D, posterior of mesopectus and mesocoxa, posterior view; E, mesopectus and mesocoxae, posteroventral view. F, Tanaostigmodes sp., mesosoma, ventral view. G & H, Leptoomus janzeni: G, head and antenna, frontal view; H, head and mesosoma, dorsolateral view. See ‘Material and methods’ for abbreviations.

FIGURE 3. A‒C, Leptoomus janzeni, specimen LF2002: A, lateral habitus (mirrored image, arrow points to posterior margin of mesocoxa); B, head in frontal view; C, ventral habitus (mirrored image). D & E, Aspidopleura baltica, holotype: D, head and mesosoma, dorsal; E, mesosoma, dorsolateral. F & G, Metapelma sp.: F, mesosoma, dorsal; G, mesosoma, lateral. H, Calosota aestivalis, mesosoma, dorsolateral. See ‘Material and methods’ for abbreviations.