Archaeomegalomus burmiticus, Nakamine & Yamamoto & Takahashi, 2022

Nakamine, Hiroshi, Yamamoto, Shûhei & Takahashi, Yui, 2022, Archaeomegalomus gen. nov.: A remarkable new brown lacewing from mid-Cretaceous Kachin amber from northern Myanmar (Neuroptera: Hemerobiidae), Zootaxa 5178 (4), pp. 380-390 : 383-386

Archaeomegalomus burmiticus sp. nov.

( Figs. 1–3 , 5 )

Diagnosis. As for the genus (vide supra).

Description. Body. Length ca. 3.7 mm as preserved (measured from vertex to apex of the abdomen).

Head. Eyes large, protruding laterally. Antennae: scapus relatively short, ca. 2 times as long as wide; pedicellus one-half length of scape; both scattered with thin setae; flagellum moniliform, relatively long, composed of 38 flagellomeres, with scattered fine setae on each segment. Maxillary palpi 4 or 5 segmented; labial palpi 3 segmented.

Thorax. Pronotum rather short, poorly preserved, covered with thin setae. Mesothorax and metathorax covered with thin setae.

Legs. Foreleg slender; procoxa poorly preserved, relatively long; profemur ca. 0.8 mm long, scarce setae; protibia ca. 0.5 mm long, slightly swollen at the middle, covered with dense thin setae, paired tibial spurs; protarsus five segmented, all tarsomeres covered with thin setae, pretarsal claws thin, small. Midleg slender; mesocoxa short; mesofemur ca. 0.9 mm long, scarce setae; mesotibia ca. 0.9 mm long, only slightly swollen at the middle to apex, covered with dense thin setae, paired tibial spurs; mesotarsus five segmented, all tarsomeres covered with thin setae, pretarsal claws thin, small. Hindleg slender; metacoxa short; metafemur ca. 0.9 mm long, scarce setae; metatibia ca. 1.5 mm long, slightly curved, only slightly swollen at the middle to apex, covered with dense thin setae, paired tibial spurs ( Fig. 3E ); metatarsus five segmented, all tarsomeres covered with thin setae, pretarsal claws thin, small.

Wings. Forewing hyaline ( Fig. 2A, B ), oval with subacute apex, ca. 5.5 mm long, ca. 2.3 mm wide (right forewing); ca. 5.3 mm long, ca. 2.0 mm wide (left forewing). Trichosors present along the entire wing margin, one trichosor between adjacent veins; marginal portions of veins and trichosors with tufts of thin setae; thin setae sparsely present on dorsal and ventral surfaces of longitudinal veins, but absent on crossveins. Costal space broad, narrowed distally; humeral veinlets recurrent, pectinately branched, most subcostal veinlets once to twice forked. Sc fused with RA at distal fourth ( Fig. 3A ). Subcostal space, proximal crossvein (1sc-r) located at origin of RP, intermediate crossvein (2sc-r) present. RP stemed single origin, with nine branches, most proximal branch deeply forked at the near stem, all branches terminally forked rather shallowly once or twice; five (right forewing) or six (left forewing) third series intra-crossveins and ten (left forewing) or eleven (right forewing) forth series intra-crossveins present. Three ra-rp crossveins (2ra-rp, 3ra-rp, and 4ra-rp) present. M divided into MA and MP, MP deeply forked; two third series intra-crossveins and three fourth series intra-crossveins present. Three r-m crossveins (2r-m, 3r-m, and 4r-m) present. Long radiomedial flexion line clearly discernible. Cu divided into CuA and CuP, CuP close to wing base; CuA pectinately branched, with four branches, most proximal branch deeply forked; CuP deeply forked; all branches terminally forked shallowly once or twice; one second series intra-crossvein and six fourth series intra-crossveins present. Three m-cu crossveins (1m-cu, 2m-cu, and 4m-cu) present. Short mediocubital flexion line clearly discernible. Three anal veins present, poorly preserved; A1 deeply forked. Two cu-a crossveins (1cu-a and 4cu-a) present. Cubitoanal flexion line clearly discernible.

Hind wing hyaline ( Fig. 2C, D ), elongate-ovoid, ca. 4.6 mm long, ca. 1.8 mm wide (right hind wing); dark brown on pterostigmal area. Trichosors present from the pterostigmal area of costal margin to along the entire wing margin, one trichosor between adjacent veins; marginal portions of veins and trichosors with tufts of thin setae; thin setae sparsely present on dorsal and ventral surfaces of longitudinal veins, but absent on crossveins. Costal space narrowed; humeral lobe triangular, humeral plate bears dense bristles; almost subcostal veinlets simple, five veinlets forked at distal (left hind wing). Subcostal space one crossvein (3sc-r) present ( Fig. 3B ). RP divided into seven branches; most proximal branche (RP1) loop like vein at the near stem (right hind wing), deeply forked; one second series intra-crossvein and eight third series intra-crossveins present. Two ra-rp crossveins (1ra-rp and 3ra-rp) present, 1ra-rp long and slightly sinuate. M divided into MA and MP, one intra-crossvein (3ma-mp) present. Three r-m crossveins (1r-m, 2r-m, and 3r-m) present, basal 1r-m long and sinuate. Cu divided into CuA and CuP; CuP close to wing base: CuA pectinately branched, with six (right hind wing) or five (left hind wing) branches; one third series intra-crossvein present. Two m-cu crossveins (1m-cu and 3m-cu) present. Anal vein poorly preserved; A1 deeply forked. Two cu-a crossveins (1cu-a and 3cu-a) present.

Abdomen. Visible in right lateral view ( Fig. 3F ), poorly preserved, but posterior part rather well preserved. Tergite 6 and 7 developed each posterior margin. Terminal segment unclear. Gonocoxite 9 visible, scattered setae on surface; gonostylus of gonocoxite 9 well developed. Ectoproct poorly preserved.

Material. HOLOTYPE: a nearly complete female adult ( Fig. 1 ), partly unobservable due to cracks, preserved in approximately 14 mm × 7.5 mm × 4 mm flat drop-shaped, yellow, transparent amber piece; specimen accession number AMNH Bu-SY31.

Type locality and horizon. Hukawng Valley (26° 20′ N, 96° 36′ E), Kachin State, northern Myanmar; midCretaceous, upper Albian to lower Cenomanian .

Etymology. The specific epithet ‘ burmiticus ’, noun in apposition, refers to the occurrence of the fossil in Burmese amber (burmite) from northern Myanmar.

Remarks. The distal parts of Sc and RA in the forewing are separated in nearly all extant Hemerobiidae , except for Adelphohemerobius Oswald, 1994 (see Oswald 1994: fig. 1; Monserrat 1997: fig. 116). In contrast, in the Mesozoic Hemerobiidae , Hemeroberotha sinefurca Makarkin, 2020 is the only species in which the distal part of Sc and RA in the forewing are definitely separated, while the others are fused ( Table 1 ). This trait is probably a plesiomorphic condition in the Hemerobiidae .

Figures

FIGURE 1. Habitus and wing detail of Archaeomegalomus burmiticus gen. et sp. nov., holotype (AMNH Bu-SY31) in mid- Cretaceous Kachin amber. A, left lateral view; B, right lateral view. Scale bar: 1.0 mm.

FIGURE 2. Wing venation of Archaeomegalomus burmiticus gen. et sp. nov., holotype (AMNH Bu-SY31) in mid-Cretaceous Kachin amber. A, right forewing; B, left forewing; C, right hind wing; D, left hind wing. Abbreviations: A1–A3: first to third anal vein; CuA: cubitus anterior; CuP: cubitus posterior; hv: humeral vein; MA: media anterior; MP: media posterior; RA: radius anterior; RP: radius posterior; Sc: subcosta. Scale bar: 1.0 mm.

FIGURE 3. Details of Archaeomegalomus burmiticus gen. et sp. nov., holotype (AMNH Bu-SY31) in mid-Cretaceous Kachin amber. A, Sc and RA on right forewing; B, Sc and RA on left hind wing; C, right lateral view of head and thorax; D, dorsal view of head and thorax; E, left metatibia and tarsus; F, right lateral view of terminalia.Abbreviations: ect: ectoproct; gx9: gonocoxite 9; hp: humeral plate; hv: humeral veinlet; lp: labial palpus; mp: maxillary palpus; mtti: metatibia; RA: radius anterior; Sc: subcosta; st: gonostylus of gonocoxite 9; ts: tibial spurs. Scale bars: 0.1 mm for A and B; 0.5 mm for C–E; 0.2 mm for F.

FIGURE 5. Distribution map and forewing venation of Mesozoic Hemerobiidae. A, distribution map of Mesozoic Hemerobiidae; B, Promegalomus anomalus (modified after Panfilov 1980, fig. 91); C, Cretomerobius disjunctus (modified after Ponomarenko 1992, fig. 4); D, Cretoneuronema jarzembowskii (modified after Liu et al. 2022, fig. 3); E, Archaeomegalomus burmiticus gen. et sp. nov.; F, Hemeroberotha sinefurca (modified after Makarkin & Gröhn 2020, fig. 4); G, Plesiorobius canadensis (modified after Klimaszewski & Kevan 1986, fig. 2).

Tables

TABLE 1. Venation in Mesozoic Hemerobiidae.

Taxon	Deposit	Distal part of	Number of	Reference
		Sc and RA in	stem of RP in
		the forewing	the forewing
Promegalomus anomalus	Late Jurassic, Kazakhstan	? (probably	three	Panfilov 1980: fig.
Panfilov, 1980		fused)		91
Purbemerobius medialis	Early Cretaceous, late Berreiasian,	?	?	Jepson et al. 2012:
Jepson, Makarkin and Co-	Durlston Formation, England,			fig. 16
ram, 2012	United Kingdom
Cretomerobius disjunctus	Early Cretaceous, Mongolia	fused	three	Ponomarenko 1992:
Ponomarenko, 1992				fig. 4
Hemeroberotha sinefurca	Mid-Cretaceous, earliest	separated	single	Makarkin & Gröhn
Makarkin and Gröhn, 2020	Cenomanian, Myanmar			2022: fig. 4
Cretoneuronema jarzem-	Mid-Cretaceous, earliest	fused	two	Liu et al. 2022: fig.3
bowskii Liu, Chen and	Cenomanian, Myanmar
Zhuo, 2022
Archaeomegalomus bur-	Mid-Cretaceous, earliest Cenoma-	fused	single	this study
miticus gen. et sp. nov.	nian, Myanmar
Plesiorobius sibericus	Late Cretaceous, Cenomanian,	fused	single	Makarkin 1994: figs.
Makarkin, 1994	northeastern Russia			9–12
Plesiorobius cf. canadensis	Late Cretaceous, Santonian,	?	single	Makarkin 1994: fig.
Klimaszewski and Kevan,	Taymyr amber, northern Siberia			13
1986
Plesiorobius canadensis	Late Cretaceous, Campanian,	fused	single	Klimaszewski &
Klimaszewski and Kevan,	Canadian amber			Kevan 1986: figs.
1986				1, 2