Longiantennum fashengi Liang, Li & Yao, 2022

Hakim, Marina, Azar, Dany & Huang, Di-Ying, 2023, First record of fossil psocodeans in copula from mid-Cretaceous Burmese amber, Zootaxa 5396 (1), pp. 74-93 : 84-89

Longiantennum fashengi Liang, Li & Yao, 2022

( Figs 7–10 )

Additional material. NIGP171866; one male (NIGP171866-a) and one female (NIGP171866-b) preserved in mating position ( Fig. 7 ), no syninclusions. The material is deposited at the Nanjing Institute of Geology and Palaeontology , Chinese Academy of Sciences, Nanjing, China .

Locality and horizon. Burmese Kachin amber (Burmite), from an amber mine located near Noije Bum Village, Tanai Township, Hukawng Valley, Myanmar; mid-Cretaceous.

Description. Head: relatively triangular in shape, with sparse setae on vertex and frons; epicranial suture present with coronal suture well pronounced from base of head capsule to ocelli and frontal suture absent, possibly limited to only base of the arms. Compound eyes globulous, half spheres in shape, flattened dorso-ventrally; ommatidia not setose. Three ocelli present, disposed in narrow inverted triangle at middle of vertex. Antennae ( Fig. 8A ) slightly shorter than body, scarcely setose; scape and pedicel elongate, 2–3× the width of flagellomeres; 32 short flagellomeres (longest preserved antenna in female), no secondary annulations. Postclypeus bulged. Maxillary palpus four-segmented ( Fig. 8B ), with numerous long setae; strong short spur sensillum near base of second maxillary palpomere. Labial palpomeres weakly visible, apical segment setose, lobe shaped. Lacinia present, bicuspid, outer cusp without visible apical denticles ( Fig. 8C ).

Thorax: Prothorax collar-like, few setae visible near edge; mesothorax well developed, triangular, setose. Legs: all segments setose; hind tibiae with row of spurs, all tibiae with two longer apical spines ( Figs 8D–E ); tarsi three-segmented, basal tarsomere the longest, fore and middle tarsomeres about equal in length, basal and middle tarsomere bearing two apical spurs; claws sharply curved, with one strong preapical tooth, without pulvillus ( Fig. 8F ). Forewing ( Fig. 8G ; measurements are taken from male) membranous, translucent; membrane not setose; wing margin with short fringe only at base of costal margin; all veins except CuP with one row of setae; stems R and M+CuA separating at 0.24 mm from wing base; Sc setose, well developed, curving perpendicularly into R 1; no veinlet present between Sc and anterior wing margin; Sc’ directed upward, almost perpendicular to wing margin; R 1 straight, connected to Rs by short crossvein; Pt elongated, narrow at base and wide at apex, four-angled (trapezoid in shape), transparent with membrane not setose; Rs and M fused for a short length, 0.06 mm long; Rs forked into R 2+3 and R 4+5 at 0.93 mm, fork R 2+3 and R 4+5 longer than stem Rs after separation from M; basi-radial cell elongated, four-angled; radial cell seven-angled, short; M+CuA branching into stems M and CuA at 0.51 mm; M with three branches; M 3 emerging first at 0.91 mm, M 1 and M 2 splitting at 1.10 mm, fork M 1 +M 2 longer than common stem M 1+2; fork of CuA at 0.65 mm; CuA 1 and CuA 2 long, curved, convex, CuA 2 half the length of CuA 1; AP free, semielliptic in shape, relatively short; CuP thinner than other veins; A clearly visible; CuP and A meeting at wing margin; in-flight wing-coupling structures present, composed of separate and curved setae. Hind wing ( Fig. 8G ) translucent, without setae on membrane, wing margin or veins; Sc short, not reaching margin; basi-radial cell present, four-angled; R 1 and Rs separating before fusion of Rs with M; Rs, M and A forked; CuA simple; CuP thin, simple.

Abdomen: Partially obstructed in ventral view by male hind leg and several fractures over male and female. Epiproct and paraprocts setose; paraproct with apical spine. Male genitalia: hypandrium simple, apically rounded, setose; female genitalia: ovipositor with well-developed external valvulae, membranous, elongated and very broad with multiple very thin long setae; one broad membranous structure visible between paraprocts and external valvulae ( Fig. 9 ).

Measurements. Male. Head length 0.44 mm, width 0.41 mm (compound eyes included), 0.24 mm (compound eyes excluded); compound eyes length 0.18 mm, width 0.09 mm. Thorax length 0.42 mm, maximum width 0.32 mm; prothorax length 0.03 mm, mesothorax length 0.17 mm, metathorax length 0.22 mm; Fw length 1.49 mm, width 0.55 mm. Abdomen length 0.81 mm, maximum width 0.35 mm. Tarsi length: Ft1 0.11 mm, Ft2 0.04 mm, Ft3 0.04 mm, Mt1 0.13 mm, Mt2 0.04 mm, Mt3 0.04 mm, Ht1 0.17 mm, Ht2 0.04 mm, Ht3 0.05 mm.

Female. Head width 0.43 mm wide (compound eyes included), 0.30 mm (compound eyes excluded), compound eyes length 0.18 mm, width 0.10 mm. Thorax length 0.43 mm, maximum width 0.31 mm; prothorax length 0.02 mm, mesothorax length 0.20 mm, metathorax length 0.21 mm; Fw length 1.42 mm, width 0.50 mm. Abdomen length 0.64 mm, maximum width 0.30 mm.

Additional description. Two individuals are encapsulated within the same amber piece, preserved in a mating position. They both appear similar in size, facing opposite directions, with their heads oriented away from each other and their abdomens directed towards one another at terminalia level, but not in direct contact. The male’s genital organs remain completely internalised.

Remarks. In specimen NIGP171866-b, one forewing has a very short common stem M 1+2 ( Fig. 8G ), though it is not observed in the second wing or in the male. Wing venation teratisms were also reported in the holotype of Longiantennum fashengi ( Liang et al., 2022) .

The discovery of a male individual belonging to Longiantennum suggests that male genitalia is mainly internalised—the only external structure being the hypandrium—, as it is usually found in non-parasitic Psocodea , which warrants a hypothesis that both holotype CNU-PSO-MA-2016020 and paratype CAU-BA-LFY-21003 are actually female specimens, possibility of two different species based on the descriptions of Liang et al. (2022). We examined the holotype CNU-PSO-MA-2016020, but could not observe any structures to suggest the presence of the hypandrium. In fact, no genitalia structures are clearly visible in ventral view; two membranous rod-like lobes are distinguished in lateral view. We believe that the structures identified originally as parameres in holotype CNU-PSO-MA-2016020 could be the setose external valvulae and the darkish edge of the originally identified hypandrium is the apex of the female subgenital plate. We note that the external valvulae in NIGP171866-b appear to be wider and longer than those of the holotype, though we cannot confirm whether it is a diagnostic difference or an artifact of preservation in the resin. The collection of more material belonging to Longiantennum would help to clarify this character.

The only other difference between CNU-PSO-MA-2016020 and specimens of NIGP171866 according to the description by Liang et al. (2022) is the absence/presence of a sensillum on the second maxillary palpomere. However, the sensillum is a very delicate character to observe—especially without an optical microscope—as the palpomeres are not always well positioned for an optimal observation. It is present in both the male and female in NIGP171866, and we could vaguely see what might be a sensillum in CNU-PSO-MA-2016020. Thus, we tentatively assign the new individuals to Longiantennum fashengi , and refrain from establishing a new species—until definitive diagnostic traits are discovered on future new specimens.

Figures

FIGURE 7. Longiantennum fashengi, NIGP171866, male (right side) and female (left side) in mating position. A, Habitus in dorsal view. B, Habitus in ventral view. Scale bars = 0.5 mm.

FIGURE 8. Longiantennum fashengi. A, Antenna, under green fluorescence. B, Maxillary palpomere. C, Lacinia. D, Fore tibia and tarsus. E, Hind tibial spines. F, Claw. G, Wings, under green fluorescence. Scale bars = 0.2 mm for G, 0.1 mm for A, 0.05 mm for B, D, E, 0.02 mm for C, F.

FIGURE 9. Longiantennum fashengi. A, B, Details of genitalia. Scale bars = 0.1 mm.

FIGURE 10. Longiantennum fashengi, hand drawings. A, antennae (female). B, forewing (male). C, Hind wing (female). D, Genitalia. Scale bars = 0.2 mm for A–C, 0.1 mm for D.