Sinahemeroscopus magnificus, Huang, Di-Ying & Nel, André, 2010

Huang, Di-Ying & Nel, André, 2010, Sinahemeroscopus magnificus, new genus and species of ‘ libelluloid’ dragonfly from the Chinese Mesozoic (Odonata, Anisoptera: Nannogomphidae?), Zootaxa 2388, pp. 44-48 : 45-47

Sinahemeroscopus magnificus sp. nov.

Figs. 1–3

Diagnosis. As for the genus.

Material. Holotype NIGP 148315 (print and counterprint of a complete forewing), deposited in Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing.

Etymology. Named for the wonderful state of preservation of the type specimen.

Age and locality. Lower Cretaceous, Yixian Formation; Liutiaogou Village, Ningcheng County, Inner Mongolia, China.

Description. Forewing hyaline, length 48.6 mm; width at nodus 10.9 mm; distance from base to nodus 26.3 mm (nodus situated in a relatively distal position at about 55% of wing length); distance from nodus to pterostigma 12.5 mm; distance from base to arculus 6.1 mm; Ax1 and Ax2 aligned and stronger than the other antenodals (bracket-like); Ax1 1.1 mm basal of arculus and Ax2 5.2 mm distal of Ax1; no secondary antenodal cross-vein between Ax1 and Ax2; distal of Ax2 seven secondary antenodal cross-veins between the costal margin and ScP, not aligned with seven corresponding secondary antenodals between ScP and RA; four antesubnodal cross-veins with a distinct gap near arculus and a long ‘cordulegastrid gap’; seven postnodal cross-veins between nodus and pterostigma, non-aligned with five corresponding postsubnodal cross-veins; no ‘libelluloid gap’ (sensu Bechly 1996) of the postsubnodal cross-veins directly distal to subnodus; pterostigma 4.5 mm long and max. 0.7 mm wide; its distal side more oblique than its basal side; pterostigma distinctly braced and covering two cells; pterostigmal brace vein aligned with basal margin of pterostigma; arculus close to Ax1 and kinked; bases of veins RP and MA (sectors of arculus) separated at arculus; hypertriangle 5.9 mm long and max. 0.7 mm wide; hypertriangle free; discoidal triangle elongate and free; length of basal side of discoidal triangle 2.5 mm; length of costal side 4.1 mm; distal side straight, 4.3 mm long; a well-defined pseudo-anal vein PsA (= AA0) delimiting a free subdiscoidal triangle (length 2.2 mm; width 1.8 mm); basal space free; cubital cell free (except for CuP-crossing and PsA); CuP-crossing 1.6 mm basal to arculus; anal area max. 2.9 mm wide with two rows of cells; cubito-anal area max. 3.4 mm wide with 2–3 rows of cells; CuA with four posterior branches; MP ending only slightly distal to level of nodus; basal postdiscoidal area with two rows of cells; post-discoidal area narrow (width near discoidal triangle 3.2 mm; width at hind margin 6.3 mm); no Mspl and no other intercalary veins in postdiscoidal area; RP 3/4 and MA undulate, but parallel with one row of cells between them; first branching of RP (= midfork) 7.2 mm basal of subnodus (second branching of RP); IR2 originating at RP 1/2; RP 2 aligned with subnodus; only one lestine oblique vein ‘O’ between RP 2 and IR2, 4.1 mm and four cells distal of subnodus; a single bridge cross-vein between RP 2 and IR2 basal to subnodus; RP 2 and IR2 divergent, basally with one row off cells, and distally with 2–4 rows of cells in-between; no well-defined Rspl; RP 1 and RP 2 parallel basally with only one row of cells between them, but near pterostigma becoming divergent with five rows of cells between them at wing margin; pseudo-IR1 weak and short distal to pterostigma; two row of cells between pseudo-IR1 and RP 1, and four rows of cells between pseudo-IR1 and RP 2.

Discussion. Sinahemeroscopus has the distal part of antesubnodal area free of cross-veins (‘cordulegastrid gap’), RP 3/4 and MA slightly undulating, all synapomorphies of the Cavilabiata Bechly, 1996. Within this clade, Sinahemeroscopus lacks synapomorphies of Cordulegastrida Bechly, 1996, viz. wings with a basal furcation of IR2 basal of the lestine oblique vein; pterostigmal brace vein reduced. But it does have the forewing synapomorphies of the Cristotibiata Bechly, 2003 (= Neopetaliidae and Brachystigmata), viz. pterostigmata not parallel sided (distal side more oblique than basal side), and stout with length less than eight times width; forewing nodus shifted distinctly distal of midwing position (reversed in Libellulidae ). Within this group, it lacks synapomorphies of Neopetaliidae Tillyard and Fraser, 1940 : intercalary vein IR1 secondarily long and straight and forked; but it has those of its sistergroup Brachystigmata Bechly, 1996, viz. wings with relatively short pterostigmata covering only 1–3 complete cells; RP 3/4 and MA strictly parallel up to the hind margin (character present in Sinahemeroscopus after the shape of these veins and the length of missing part of posterior wing margin that corresponds exactly to the distance between these two veins); and area between RP 2 and IR2 distally distinctly widened, with more than one cell row in the distal half.

Sinahemeroscopus has the forewing characters of the Mesozoic family Hemeroscopidae Pritykina, 1977 (sensu Bechly et al. 1998): forewing subdiscoidal triangle free; postnodal cross-veins not aligned with postsubnodal cross-veins; Mspl absent; Rspl rudimentary, with one row of cells between it and IR2; pseudo- IR1 short; Ax1 and Ax2 stronger than secondary antenodal cross-veins and with few (1–4) secondaries between them; area between IR2 and RP 2 distally strongly widened, with two-four rows of cells between them; one oblique cross-vein ‘O’ four cells distal of subnodus. Bechly et al. (1998) placed Hemeroscopus Pritykina, 1977 and Prohemeroscopus Bechly et al., 1998 in Hemeroscopidae .

Nevertheless Sinahemeroscopus has the putative synapomorphies of the Mesozoic family Nannogomphidae, sensu Bechly (2003): forewing Ax2 shifted basal to level of distal angle of the discoidal triangle (convergent to Paneurypalpidomorpha); Ax1 and Ax2 are relatively close together with not more than one secondary antenodal cross-vein between them. Bechly (2008) later transferred Prohemeroscopus to the Nannogomphidae because it has putative synapomorphies of Nannogomphidae, unlike Hemeroscopus, which has Ax2 opposite or distal to distal angle of discoidal triangle and 3-4 secondaries between Ax1 and Ax2.

Sinahemeroscopus differs from Hemeroscopus by the number of secondary antenodal cross-veins between the two primaries and the position of Ax2, but also by presence of a distinctly oblique pterostigmal brace (reduced in Hemeroscopidae ). It differs from Nannogomphus by its relatively longer pterostigma, more elongated discoidal triangle, more numerous secondary antenodals, wider area between IR2 and RP 2 (Bechly et al. 1996; Bechly 2003). Sinahemeroscopus differs from Prohemeroscopus by its free and more elongate discoidal triangle, and postdiscoidal area with only two rows of cells just distal of discoidal triangle, instead of four rows ( Bechly et al. 1998).

Ren et al. (2003) described the Chinese Early Cretaceous genus Abrohemeroscopus and placed it in Hemeroscopidae . Its primary antenodal cross-veins are apparently not very well preserved but it seems that Ax2 is opposite the distal angle of discoidal triangle and that there are more than two secondaries between the two primaries, as in Hemeroscopidae , and unlike the Nannogomphidae. Sinahemeroscopus also differs from Abrohemeroscopus in the presence of five rows of cells in the distal area between IR2 and RP 2, and only two rows of cells in postdiscoidal area.

We admit as valid the synapomorphies proposed by Bechly (2008) for the Nannogomphidae, and Sinahemeroscopus falls in this family based on the forewing venation. We provisionally place it in Nannogomphidae pending information on its hindwing, which may allow us to determine whether its anal loop will be broad as in Hemeroscopus or relatively smaller as in Nannogomphus or Prohemeroscopus.

Figures

FIGURE 1. Sinahemeroscopus magnificus gen. et sp. nov., holotype NIGP 148315, photograph of print (scale bar represents 10 mm).

FIGURE 2. Sinahemeroscopus magnificus gen. et sp. nov., holotype NIGP 148315, photograph of counterprint (scale bar represents 10 mm).

FIGURE 3. Sinahemeroscopus magnificus gen. et sp. nov., holotype NIGP 148315, drawing of forewing. Standard abbreviations: AA anal vein, Ax 1 Ax 2 primary antenodal cross-veins, CuA cubitus anterior, IRi intercalary radial veins, MA median anterior, MP median posterior, N nodus, ‘ O’ lestine oblique vein, Pt pterostigma, RA radius anterior, RP radius posterior, T discoidal triangle (scale bar represents 10 mm).