Grandixyela rasnitsyni Zheng, 2021

Zheng, Yan, Kopylov, Dmitry S., Zhang, Qi, Zhang, Hai-Guang, Qin, Min, Chen, Jun & Zhang, Hai-Chun, 2021, Discovery of a new symphytan wasp in the mid-Cretaceous Kachin amber (Hymenoptera, Syspastoxyelidae), Palaeoentomology 4 (6), pp. 629-636 : 631-634

Grandixyela rasnitsyni Zheng , sp. nov.

( Figs 1 , 2 )

Holotype. Male , NIGP177617 , mid-Cretaceous Burmese amber, kept at Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences ( NIGP); a complete and well-preserved fossil insect specimen except that surface of head and thorax is covered with small air bubbles obscuring details.

Etymology. The species is named in honor of Professor Alexandr Pavlovich Rasnitsyn, a well-known palaeoentomologist who has made great contributions to the study of hymenopteran fossils.

Diagnosis. As for genus.

Locality and horizon. Hukawng Valley, Kachin State, northern Myanmar; mid-Cretaceous.

Description. Male. Body large, 4.93 mm long (in dorsal view, from labrum to end of hypopygium; Fig. 1A, B ).

Head ( Fig. 1C ) oval and broad, clearly wider than thorax, 1.30 mm wide and 1.01 mm high (assessed except for the mandibles), with no occipital carinae or visible cuticular bridge between mouth cavity and occipital foramen. Compound eyes nearly suboval, bulging, short (occupying less than half head length), reaching head margin. Ocelli not visible. Clypeus transverse, with fore margin triangular. Antenna 15-segmented ( Fig. 1C ), 1.66 mm in length, 0.10 mm in maximum width; scape elongate and clavate, 0.31 mm length × 0.09 mm width; pedicel globular, short and broaden, 0.10 mm × 0.07 mm; first flagellomere elongate and thickened (0.51 mm × 0.10 mm), shorter than antennal thread; antennal thread 0.74 mm × 0.03 mm, narrow (0.30 × as wide as 1 st flagellomere), gradually reducing in width apically. Mandibles scythe-like, crossed widely scissor-like beyond the frontoclypeal area, oriented ventrally, with apical tooth about 0.38 mm length and 0.07 mm width (basal part of mandible invisible). Maxillary palp leg-like, with four segments visible, 0.27 mm, 0.24 mm, 0.20 mm and 0.09 mm, respectively, neither distinctly incrassate. Labial palp not visible.

Mesosoma rectangular, 1.35 mm long and 0.97 mm wide across tegulae. Pronotum not elongate, wider than long, 0.42 mm long and 0.70 mm wide. Mesonotum small, apparently triangular, with details obscure. Metanotum short, with no details visible. Legs slender, mid coxa small, trapezoid, mid trochanter and trochantellus elongate, all tibiae with two strong apical spurs, mid one with 2 pairs of preapical spurs lower pair being subapically places N1 = pronotum, shorter than wide (0) or longer than wide (1); No = notauli, meeting before mesoscutellum (0) or widely separated at mesoscutellum (1); NF = antennal thread, 8-segmented (0) or 12-segmented (1); F1 = first flagellomere in respect to antennal thread (disal flagellomeres), shorter (0) or longer (1); Pt = pterostigma type, wide (0) or narrow (1) or sclerotised (2) or unsclerotised (3); 1-RS = first radial sector dot-like (0) or linear (1); 4-RS-Pt = fourth section of RS, gently curved (0) or strongly curved (1), ending to pterostigma before its apex (2) or ending to pterostigma beyond its apex (3); 1mcu = cell, slightly longer than high (0) or twice as long as high (1); r-m - 2cu-a = crossveins r-m meeting 2cu-a, aligned (0) or distinctly angled (1); T1 = fore tibia with row of short thick setae at flexor surface, present (0) or absent (1); F2 = mid femur, almost disk-like swollen (0) or normal (1) .

(less clear for hind tibiae); all tibiae with numerous sharp spines dorsal and apical, fore tibia also with ventral spines (on its flexor surface). Fore leg ( Fig. 1D ) with femur 0.92 mm long and 0.16 mm wide, tibia 0.66 mm long, 0.13 mm maximum wide and 0.04 minimum wide, tarsi 5- segmented, with middle tarsomeres unusually short and apical one unusually long (tarsomeres lengths ratio: 0.28: 0.06: 0.07: 0.055: 0.25). Mid femur 0.75 mm long and 0.16 names indicated. Symbols: md = mandible, lr = labrum, cly= clypeus, pmx = maxillary palp, sti = stipes, N 1 = pronotum, N 2 = prescutum, pl 1 = propleuron, cx2 = mesocoxa, cx3= metacoxa, cr = cercus, gcx = gonocoxa, gsty = gonostylus. Scale bars = 1 mm.

mm wide, tibia 0.57 mm long and 0.04 mm (minimum) to 0.10 mm (maximum) wide, tarsi 5-segmented, with basitarsomere 0.49 mm long and 0.04 mm wide, segments 2–4 slightly wider than basitarsomere, 5 th segment 0.18 mm long and 0.04 mm maximum wide. Hind coxae and trochanter ambiguous, femur swollen and spindle-like, with 1.05 mm long and 0.27 mm wide; tibia 1.10 mm long and 0.14 mm wide, tarsus length 0.70 mm, segments 2–4 wider than 1 or 5, the tarsomeres lengths ratio: 0.35: 0.06: 0.04: 0.05: 0.20. Claws large, acute and hooked apically, with small basal tooth, long lobe and big arolium ( Fig. 1E ).

Forewing 3.45 mm long and 1.34 mm wide, with about apical 40% veinless, densely and regularly corrugated parallel to wing axis. Costal area narrow. Pterostigma ( Fig. 1F ) narrow, completely sclerotised, 0.61 mm long and 0.17 mm wide. SC absent. R straight, strongly broaden basally, especially R + M + Cu section. 1-RS slightly proclined, 2× as long as vein wide, but much shorter than 1-M, 1-M distinctly arched. RS+M within cell 1mcu gently bending midway, shorter than 1- M. 1r-rs and 2 + 3-RS absent. 2r-rs present, about 0.66× as long as pterostigma wide. 4-RS slightly curved, reaching wing margin beyond pterostigmal apex for short distance. 2m-cu bent near 2r-m and slightly S-curved posteriorly. M+Cu arching basally, angled with 1-Cu. 1-Cu straight and longer than RS+M. 1m-cu long, slightly shorter than RS+M but longer than 2-Cu. 1cu-a subparallel to 1m-cu and 2m-cu, more than half of 1-Cu in length. Hind wing venation obscure.

Metasoma clearly wider than mesothorax, 2.57 mm long and 1.29 mm maximum width at fourth segment, then tapering posteriorly. Genitalia ( Fig. 1G ) with gonocoxa long, arching, tapering, gonostylus short and small as preserved (incompletely visible), with other details unusual and difficult to interpret: no usual penis valves nor evident volsellae found but something like lateral bubbles aligned to gonocoxae and margined with sclerotized stripes (better preserved material is necessary to homologize the visible structures). Cercus elongate, three-segmented: basal segment thicker, terminal segment slender.

Figures

FIGURE 1. Grandixyela rasnitsyni gen. et sp. nov., holotype. A, Dorsal view. B, Ventral view. C, Head and antenna, ventral view. D, Foreleg, dorsal view. E, Mid-, hindleg and claw, dorsal view. F, Pterostigma, ventral view. G, Genitalia, ventral view. Scale bars: A and B = 1 mm; C–G = 0.5 mm.

FIGURE 2. Line drawing of Grandixyela rasnitsyni gen. et sp. nov. A, Dorsal view. B, Ventral view. C, Forewing, vein and cell