Guocordulia boreala ( Ren & Guo, 1996 ), 2024

Nel, André, Huang, Di-Ying & Lian, Xin-Neng, 2024, Redescription of the ‘ libelluloid’ Mesocordulia boreala (Odonata: Mesocorduliidae) from the Lower Cretaceous of China, Zootaxa 5562 (1), pp. 31-37 : 32-35

Guocordulia boreala ( Ren & Guo, 1996) , comb. nov.

for Mesocordulia boreala Ren & Guo, 1996

( Figs 1 , 2 )

Material. Holotype LB94021 (female), paratype LB94022 (hind wing), Geological Museum of China, Beijing. New specimen: NIGP206353 (complete female in dorsal view).

Diagnosis (new diagnosis for genus and species). Compound eyes well separated; forewing secondary antenodals incomplete; hind wing antenodals complete; five crossveins in forewing antesubnodal area, only one in hind wing; sector of arculus well separated; a well-defined elongated anal loop with ten cells; PsA well defined in fore- and hind wings; six postnodal crossveins; subdiscoidal vein (basal part of CuA that is aligned with the distal side MAb of discoidal triangle) reduced in hind wing; hind wing CuA shortened with only one distinct dichotomic branching into CuAa and CuAb; forewing Ax2 situated distinctly above mid part of discoidal triangle; pterostigmal brace vein shifted distally beneath pterostigma.

Locality and horizon. Huangbanjigou, Beibiao City, West Liaoning, NE China; Lower Cretaceous Yixian Formation (ca. 125 Ma, lower Barremian).

Description. Specimen NIGP206353. Head 5.0 mm long, 3.5 mm wide, compound eyes large, 0.5 mm apart; ocelli disposed in triangle; thorax robust, 8.5 mm long, 5.2 mm wide; legs rather short and robust with strong spines, very similar to those of an extant Corduliidae ; fore-, mid-, hind legs uniform, metafemur distinctly larger than mesofemur, the latter distinctly larger than fore femur, inner edge bearing two longitudinal ridges covered with spines; tibiae distinctly longer than femora, metatibiae distinctly larger than mesotibiae, mesotibiae slightly larger than foretibiae, all tibiae armed with several rows of longitudinal spines, inner edges bearing a row of long spines, ca. 8; tarsi with three tarsomeres, first tarsomere very short, second long, widened apically, third tarsomere elongate, longer than first and second tarsomeres together; paired claws small. Abdomen 29.3 mm long, 3.7 mm wide, with transverse hyaline band on segments I and II; segment II without secondary genital organs (female), cerci small, no ovipositor visible. Wing hyalines. Forewing ( Fig. 2 ) 24.0 mm long, width opposite nodus 6.4 mm, distance from base to arculus 2.9 mm, from base to nodus 12.7 mm; from nodus to pterostigma 6.9 mm; from nodus to wing apex 8.9 mm; nodus nearer to apex than base of wing; pterostigma short, strong and covering one cell, about 1.6 mm long, 0.5 mm wide and with proximal and distal sides rather strongly divergent; pterostigmal brace distinctly oblique, slightly distal to basal side of pterostigma; Ax1 and Ax2 stronger than secondaries, 2.3 mm apart, four secondaries of first row not aligned with the three of second row; six postnodal crossveins; two proximal postnodal crossveins incomplete; arculus in a proximal position, only 0.9 mm distal of first antenodal crossvein and 0.5 mm basal of discoidal triangle; MA and RP clearly separated at their bases in arculus; free isosceles discoidal triangle, with anterior side straight; anterior side 1.6 mm long, proximal side 1.8 mm, distal side 1.8 mm; hypertriangle and median space free, MA arcuate at base; submedian space crossed by CuP; submedian and subdiscoidal spaces clearly separated by a strong oblique vein PsA; subdiscoidal space free; anal area not very broad, with two rows of cells; CuA not very long, with four posterior branches and reaching posterior wing margin slightly basal to level of nodus; three rows of cells in cubito-anal area; postdiscoidal area narrow, with two rows of cells distal of triangle, not widened near posterior wing margin, with four rows of small cells; no Bq crossvein and no crossvein in proximal part of area between RP3/4 and IR2, basal of nodus; five antesubnodal crossvein in space between RA and RP; no distinct Rspl; base of RP2 opposite subnodus; oblique crossvein ‘ O’ 0.8 mm, one cell distal of subnodus; area between IR2 and RP2 slightly narrowed distally, these veins converging near posterior wing margin; area between RP2 and RP1 narrow, with four rows of cells at most and a short but distinct vein IR1, no sigmoidal crossvein in proximal part of area between RP2 and RP1; no Mspl; MA and RP3/4 undulate, more or less parallel and directed obliquely to posterior wing margin.

Hind wing (Fig. 13) 23.5 mm long, 8.8 mm wide; width opposite nodus 8.0 mm; distance from base to arculus 2.7 mm, from base to nodus 9.6 mm, from nodus to pterostigma 9.3 mm, from nodus to apex 14.3 mm; nodus in a proximal position between base and apex; pterostigma 2.4 mm long, 0.7 mm wide, short, covering one cell and with proximal and distal sides divergent; pterostigmal brace distinctly oblique, slightly distal to basal side of pterostigma; three antenodal crossveins, all of same strength; five postnodal crossveins with the three proximal incomplete; arculus in a proximal position, just distal of first antenodal crossvein and nearly opposite discoidal triangle; MA and RP clearly separated at their bases in arculus; free isosceles discoidal triangle, with anterior side slightly curved; length of anterior side 2.0 mm, of proximal side 1.2 mm, of distal side 1.9 mm; hypertriangle and median space free; MA strongly arcuate at base; submedian space crossed by CuP, a free subdiscoidal space and a distinct oblique vein PsA; anal area wide, with eight rows of cells between AA and posterior wing margin; AA with three perpendicular branches directed towards posterior wing margin, no anal triangle; no anal angle distal branch of AA provides the basal side for a long and narrow ten-cells anal loop, 5.0 mm long, 1.3 mm wide, with a ill-defined zigzagged midrib; subdiscoidal vein (basal part of CuA that is aligned with the distal side MAb of the discoidal triangle) strongly reduced; gaff of CuA elongated and slightly curved; CuAa distally zigzagged, not very long, with no well-defined posterior branches, and reaching posterior wing margin well basal of nodus level; six rows of cells in cubito-anal area; postdiscoidal area narrow, distinctly broader near posterior wing margin, with two rows of cells in proximal part and 12 rows of cells along posterior wing margin; Mspl rudimentary; MA and RP3/4 not undulating, parallel and obliquely reaching posterior wing margin; no Bq crossvein; no crossvein in proximal part of area between RP3/4 and IR2, basal of nodus; only one antesubnodal crossvein in space between RA and RP; no distinct vein Rspl; base of RP2 opposite subnodus; oblique crossvein ‘ O’ 0.9 mm distal of subnodus; area between IR2 and RP2 slightly narrowed distally; IR2 and RP2 directed obliquely to posterior wing margin; area between RP2 and RP1 with 3–4 rows of cells; a short IR1, no sigmoidal crossvein in proximal part of area between RP2 and RP1.

Figures

FIGURE 1. Guocordulia boreala (Ren & Guo, 1996), comb. nov., new specimen: NIGP206353. Photographs. A, Habitus. B, Apex of abdomen. C, Head and thorax. Scale bars = 5 mm in A, 2 mm in B and C.

FIGURE 2. Guocordulia boreala (Ren & Guo, 1996), comb. nov., new specimen: NIGP206353. Photographs. A, Right wings. B, Left wings. Scale bars = 2 mm.