Largusoperla flata, Chen & Wang & Du, 2018

Chen, Zhi-Teng, Wang, Bo & Du, Yu-Zhou, 2018, Discovery of a new stonefly genus with three new species from mid-Cretaceous Burmese amber (Plecoptera: Perlidae), Zootaxa 4378 (4), pp. 573-580 : 576-577

Largusoperla flata sp. nov.

( Figs. 8–13 )

Diagnosis. As for the genus, except for the laterally thickened and upcurved paraprocts.

Description. Macropterous; body length (excluding antennae and cerci) ca. 8.2 mm, slender, generally brownish ( Fig. 8 ).

Head ( Figs. 8, 9 ): Head rounded and mostly brown, with paired compound eyes and three ocelli, a dark brown stigma covering eye area, anterior ocellus horizontal and smaller than posterior ones, which are oriented longitudinally. Antennae mostly brown, hairy and filiform, with 23 to 38 segments and apical segments thinner than basal ones. The maxillary palps slender and much longer than the labial palps.

Pronotum ( Figs. 8–10 ): Pronotum about as wide as head, near reverse trapezoidal in shape with obtuse corners, width longer than length. Mesothorax and metathorax sclerotized, with similar length to prothorax; meso- and metathoracic gill remnants present. Forelegs shortest, hindlegs longest; femur and tibia mostly brown; tibia slightly longer than femur, ventroapically with two slightly enlarged spurs; tarsi three-segmented, first two tarsal segments shortest, equal in size and with distinct euplantulae; claws simple, with sharp apices.

Forewings ( Figs. 8, 11 ): Wings length 8.0 mm, width 2.5 mm. ScP about three-fourth of total wing length, reaching ScP+RA beyond ra-rp; area between anterior margin and RA with a pale crossvein in right forewing but shows no crossveins in left forewing; 12 crossveins present between ScP and the anterior margin. RP originated near basal one-third of RA and with three branches. M forked at apical one-third of the wing length; ra-rp not connected with the opposite crossvein rp-ma. Cu forked to CuA and CuP, CuA forked basal to the fork of M, with three branches; CuP simple and straight; area between M and CuA with four crossveins in right forewing and with at least six crossveins in left forewing, 1.5X wider than area between CuA and CuP, which with five crossveins in right forewing and with at least three crossveins in left forewing. Basal AA veins not preserved, AA1 simple, AA2 with at one branch visible.

Hind wings ( Fig. 8 ): Wings length 6.9 mm, width 2.5 mm. ScP reaches RA before ra-rp; area between anterior margin and ScP with one weak crossvein; much fewer crossveins present between ScP+RA and the anterior margin. Apical parts of RP, M and Cu veins similar to forewings.

Abdomen ( Figs. 8, 12 ): Abdomen near half the length of the body, each segment with dark lateral marks and extended posterolateral margins. Sternum 9 slightly extended backwards, posteromedially with a small, slightly elevated transverse lobe. Tergum 10 sclerotized and seems cleft, without projected hemiterga. Paraproct broad, sclerotized, almost flat, subtriangular from ventral aspect; lateral margins slightly thickened and up-folded; apex slightly elevated, more sclerotized and blunt. Abdominal tip with an obscure, posteromedial subuliform structure between and beyond paraprocts. Cerci hairy and short gradually elongated and narrowed from base to apex, with 10 to 11 segments and each segment with clustered long setae.

Type material. Holotype male, NIGP167159. Pro- and meta-nota are not preserved in this specimen. Wings are overlapped so it’s hard to see the details of the basal part of the wings. Dorsal abdomen is covered by unknown, obscuring substance, so the detailed structure of tergum 10 is not visible.

Etymology. The specific epithet refers to the flat paraprocts of the holotype.

Syninclusions. Plant and woody fragments and about ten minute tiny unidentified Coleoptera, Hymenoptera, and Diptera.

Figures

FIGURES 8–13. Largusoperla flata sp. nov., holotype male. 8. HabituS, dorSal view; 9. Head and pronotum, dorSal view; 10. TarSal SegmentS; 11. Right forewing; 12. Terminalia and itS reconStruction, ventral view; 13. Terminalia and itS reconStruction, dorSal view.