Sinaktassia tangi, Lin, Qi-Bin, Nel, André & Huang, Di-Ying, 2010

Lin, Qi-Bin, Nel, André & Huang, Di-Ying, 2010, Sinaktassia tangi, a new Chinese Mesozoic genus and species of Aktassiidae (Odonata: Petaluroidea), Zootaxa 2359, pp. 61-64 : 62-63

Sinaktassia tangi sp. nov.

( Figs 1–2 )

Material. Holotype NIGP 148316, print of a complete forewing, deposited in Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing.

Age and locality. Lower Cretaceous, Yixian Formation, Western Liaoning, China.

Etymology. Named for Mr. Tang Yonggang, in gratitude for his secular help in our field work and research.

Diagnosis. As for the genus.

Description. Forewings hyaline, 87.6 mm long, 18.2 mm wide, distance from base to arculus 10.0 mm, from arculus to nodus N 32.9 mm, from N to wing apex 44.7 mm, from N to Pt 23.8 mm, from Pt to wing apex 15.9 mm; Pt parallel sided narrow elongate, proximally recessed, 6.5 mm long, 1.0 mm wide, covering nine small cells, pterostigmal brace weak, but oblique, slightly proximal to basal side of Pt; no antenodal cross-vein basal of Ax1; Ax1 8.5 mm from wing base; Ax1 and Ax2 11.2 mm apart, with three secondary cross-veins between them; Ax2 just distal of distal angle of hypertriangle; 18 antenodal cross-veins of first row and 14 of second row distal of Ax2, not aligned; nine cross-veins between RA and RP basal of base of RP 3/4, distal part of antesubnodal area with eight cross-veins; two oblique veins ‘O’ between IR2 and RP 2 three cells and 10 cells distal of subnodus; Bqs-area between RP and IR2 basal of subnodus distinctly narrowed, with nine Bqs cross-veins basal of first oblique vein ‘O’; base of RP 3/4 20.6 mm from arculus; base of RP 2 aligned with subnodus; postnodal space very narrow, 20 postnodal cross-veins, not aligned with the 24 postsubnodal cross-veins; 24 cross-veins in long area between C and RA distal to Pt; hypertriangle, median and submedian spaces free; CuP curved; subdiscoidal space large, divided into six cells and limited by a strong oblique PsA; arculus oblique; posterior part (cross-vein) of arculus shorter than anterior part [ RP & MA]; distance between arculus and T 3.5 mm; T two-celled, transverse but broad, with basal side 3.5 mm long, anterior side 4.7 mm long, distal side 5.0 mm long; 2–3 rows of cells in anal area; basal CuA long; CuAa with 6–7 posterior branches; cubital area with eight rows of cells between CuA and posterior wing margin; MP weakly curved, ending on posterior wing margin distal to N level; postdiscoidal area with three rows of cells just distal to triangle but many more near posterior wing margin; in distal part of postdiscoidal area at least four secondary longitudinal veins directed towards posterior wing margin and apparently branching from MA; no Mspl; MA and RP 3/4 weakly curved and with the area between them distally broadened, with seven rows of cells along posterior wing margin; no Rspl; in distal part of area between IR2 and RP 3/4 at least three secondary longitudinal veins directed towards posterior wing margin and apparently branching from IR2; RP 2 with a double weak curve and area between IR2 and RP 2 distally weakly broadened; base of IR1 five cells distal of second vein ‘O’, weak and zigzagged, but distal part of IR1 not zigzagged but weakly curved; cells in area between RP 1 and IR1 arranged in 2–3 polygonal groups limited by stronger secondary veins and branched on RP 1.

Discussion. The Aktasiinae comprises two Mesozoic genera Aktassia and Aeshnogomphus. Sinaktassia and Aktassia differ from Aeschnogomphus by presence of a pterostigmal brace vein (completely suppressed in the latter), and a longer area between C and RA distal of Pt. Sinaktassia differs from Aeschnogomphus buchi (Hagen, 1848), Aeschnogomphus kuempeli Bechly, 2000, Aktassia magna Pritykina, 1968 , and Aktassia pritykinae Nel et al., 1998 by the less numerous polygonal groups of cells in main areas, by presence of only three rows of cells in postdiscoidal area just distal to discoidal triangle instead of 4–5 or more, by discoidal triangle divided into two cells instead of 5–6 (visible in the Kazakhstan and Chinese material of Aktassia ), by the presence of only two rows of cells in area between RP 1 and RP 2 basal to Pt, and by IR1 basally strongly zigzagged ( Nel et al., 1998; Bechly, 2000). Further differences from Aktassia are the presence of only one row of cells between RA and RP 1 at level of Pt, and the absence of Rspl.

Remark. Zhang (1999) placed Aktassia and Aktassiidae within Aeschnidioidae (sic) and stated that Aktassia ‘has a wing venation that resembles more closely that of the genus Aeschnidium Westwood, 1854 in the Aeschnidiidae than any other known genus within the various families of Anisoptera,’ based on the following characters: ‘a nearly equilateral discoidal triangle being as high as wide, not extended longitudinally, and containing two rows of many cells (at least nine), and numerous cross-veins in the cubito-anal area.’ We believe that Zhang (1999) was in error because these characters are not synapomorphies of Aeschnidiidae ; they frequently occur in many taxa within Odonata including the Petaluroidea. Furthermore Aktassia and other taxa currently included in Aktassiidae lack synapomorphies of Aeschnidiidae as listed in Fleck and Nel (2003).

Figures

FIGURE 1. Sinaktassia tangi gen. nov., sp. nov., holotype NIGP 148316, photograph of forewing (scale bar represents 10 mm).

FIGURE 2. Sinaktassia tangi gen. nov., sp. nov., holotype NIGP 148316, drawing of forewing, standard abbreviations: AA anal vein, Ax 1 Ax 2 primary antenodal cross-veins, CuA cubitus anterior, CuP cubitus posterior, IRi intercalary radial veins, MA median anterior, MP median posterior, N nodus, ‘ O’ oblique veins, Pt pterostigma, PsA oblique crossvein separating submedian space from subdiscoidal triangle, RA radius anterior, RP radius posterior, T discoidal triangle. (scale bar represents 5 mm).