Megacoxa synchrotron Brazidec et al., 2024

† Megacoxa synchrotron Brazidec et al., 2024

Fig. 5 View Fig

Diagnosis

See Brazidec et al. (2024).

Material examined

MYANMAR • ♀; Kachin State, Myitkyina District, Hukawng Valley ; [26°20′ N, 96°36′ E]; unnamed horizon, mid-Cretaceous, upper Albian to lower Cenomanian, 98.79± 0.62 Ma ( Cruickshank & Ko 2003; Shi et al. 2012); CNU-HYM-MA-2016208 . GoogleMaps

Description

Female

BODY. Length (except ovipositor) 5.4 mm, fore wing length 3.4 mm. Specimen in slightly gritty amber piece together with small beetle (Coleoptera) and midge (Diptera); wasp well preserved except for right foreleg cut off at base of tibia and ovipositor ( Fig. 5A View Fig ) cut off approx. 0.5 mm from tip of abdomen.

HEAD. Wider than long, head capsule without prominent sculpture or setation; eyes oval ( Fig. 5B View Fig ), higher than long, without postocular carina; antennal insertions in depressions, frons overhangs them above; occipital carina well developed ( Fig. 5A View Fig ), crenulate, area around occipital foramen deeply concave; clypeus short and wide, triangular with tip between antennal insertions; antenna ( Fig. 5B View Fig ) slightly shorter than head + mesosoma combined, with short globular scapus and short flat pedicellus, antennomeres 3–14 flattened (probably an artefact), antennomeres 3–6 longer than 7–13, antennomere 14 approx. twice as long as wide, strongly tapered apically; labrum a small narrow flap below clypeus, concealed when mandibles are closed; mandibles broad, with three teeth ( Fig. 5B View Fig ) each, apical tooth longest.

MESOSOMA. With elongate, extended propectus ( Fig. 5A–B View Fig ); pronotum narrow medially, triangular laterally; fore femur spindle-shaped, fore tibia slender, with elongate, curved calcar; mesoscutum strongly arched in lateral view, angled between vertical anterior surface and horizontal surface; horizontal surface flat, level with mesoscutellum, not prominently sculptured; median mesoscutal sulcus ( Fig. 5A View Fig ) distinct, crenulate, extends to transscutal articulation; axillae distinct, triangular, abut medially, separated from mesoscutellum by oblique foveate scutoscutellar sulcus; mesoscutellum flat, smooth, pointed anteriorly, rounded posteriorly; mesosoma difficult to observe laterally because of position of legs and curvature of amber piece; mid femur spindle-shaped, mid tibia slender; hind leg much larger than fore and mid legs, hind femur strongly swollen, hind tibia ( Fig. 5C View Fig ) strongly expanded distally, widest at approx. two-thirds from proximal end, with distinct fringe of setae distally on median ventral margin, two apical tibial spurs inserted just distally of fringe, inner spur longer than outer; hind basitarsomere approx. equal in length to remaining tarsomeres; tarsal claws slender, simple.

WINGS. Fore wing ( Fig. 5D View Fig ) hyaline with veins C, R1, Sc+R, M+Cu, A, Rs+M, Rs, M and Cu fully pigmented; Rs+M aligned with M+Cu; medial cell wide distally; Rs present between Rs+M and r-rs, closing first submarginal cell; marginal cell narrow, closed in straight line by Rs; hind wing could not be observed.

METASOMA. 1.68 × as long as mesosoma, fusiform, with weak sculpture and setation in ventral view; sternum 2 tapering anteriorly, broadening posteriorly to broadest point of metasoma, approx. twice as long as sternum 3; sternum 7 strongly tapered apically, folded over medially along longitudinal axis; base of ovipositor ( Fig. 5A View Fig ) extends straight from dorsal part of metasomal tip and beyond tips of wings.

Male

See Brazidec et al. 2024.

Remarks

† Megacoxa synchrotron was described from a male and the holotype was deposited in Phyletisches Museum Jena, Germany (CASENT0753237; Brazidec et al. 2024: figs 2f, 8). The female we describe here resembles the holotype in a number of features: the antennal configuration, the crenulate median mesoscutal sulcus, the medially abutting axillae, the uniquely enlarged hind tibia ( Fig. 5C View Fig ; Brazidec et al. 2024: fig. 8a). The wing venation is virtually identical in the holotype and the present female (compare Fig. 5D View Fig with fig. 2f in Brazidec et al. 2024). The main difference between the two specimens is in their size, the female being almost twice as long as the holotype. However, such sexual dimorphism is not unusual in wood-living wasps (L. Vilhelmsen, pers. obs.). In most of the phylogenetic analyses ( Fig. 1 View Fig ), the female specimen CNU-HYM-MA-2016208 comes out in a polytomy with the three previously described species of † Megacoxa , including † M. synchrotron .