1052
Journal of Paleontology
andMAstrongly separated at arculus;MAbmore than twice as long as basal side of discoidal cell, MAb well aligned with distal free part of CuA; CuA divided into CuAa and CuAb; CuAb short, directed toward posterior wing margin and distally lost; only fragments of CuAa preserved, but CuAa and MP clearly parallel for a long distance, at least till below level of nodus, with probably one row of cells between; MP weakly curved, reaching posterior margin not far distal of nodus level, 24.0mm from wing base; MAa nearly straight, more or less parallel toMP, with one row of cells in basal part of postdiscoidal area, 1.7mm wide, this area being quite broader near posterior wingmargin with 14 rows of small cells present; Ax0 visible, very near to wing base; two primary antenodal veins very strong, Ax1 1.5mm basal of arculus and Ax2 1.7mmdistal of arculus, Ax1 nearly perpendicular to ScP and R+MA, Ax2 distinctly oblique; no secondary antenodal crossvein visible; five preserved antesubnodal crossveins between arculus and subnodus; base of RP3/4 6.5mm distal of arculus, closer to nodus than to arculus; base of IR2 very close to that of RP3/4, 1.4mm distally, originating distinctly from RP; nodal crossing and subnodus oblique; nine postnodal crossveins between C and RA not strictly aligned with the seven postsubnodal crossveins between RA and RP1; an oblique pterostigmal brace vein; only one crossvein below peterostigma; pterostigma not basally recessed, 4.3mm long and strong, 0.9mm wide; C and RA thickened along pterostigma; area between C and RA distal of pterostigma with six crossveins; RP2 not aligned with subnodus; two visible bridge crossveins; one oblique vein “O,” and one cell 1.3mm distal of base of RP2; RP2 nearly straight; area between RP1 and RP2 with two rows of cells basal of pterostigma; base of IR1 three cells distal of subnodus, IR1 strongly zigzagged; base of pseudo-IR1 below distal side of pterostigma; pseudo-IR1 short and straight; area between MAa and RP3/4 widened distally; area between RP3/4 and IR2 strongly widened distally; area between IR2 and RP2 distally widened, with six to seven rows of cells along posterior wing margin; area between RP2 and IR1 progressively widened, with four rows of cells along posterior wing margin; area between pseudo-IR1 and RP1 not distally widened. Abdomen parallel-sided, stout, and rather smooth (no setae
or spines appear), with apex not preserved, at least 41.0mm long, 4.5mm wide; transverse carina visible (sensu Asahina 1954); no secondary genital apparatus visible (female); complex pattern of coloration preserved (see Figs. 2, 4). Thorax stout, about 14.0mm long and 8.0mm wide;
dorsal, ventral, and internal parts are heavily compressed and difficult to interpret. Fragments of legs are visible but incomplete. Nevertheless, they look strong. Head absent.
Etymology.—Named difficilis for the very delicate preparation of the holotype, before study.
Remark.—The pattern of coloration of the abdomen of this taxon is simpler than those of many extant Odonata but similar to those of the Epiophlebiidae.
Discussion
This fossil belongs to the clade Isophlebioptera Bechly, 1996 for the hindwing subdiscoidal space strongly expanded with a bulged posterior margin. Furthermore, it has all the characters of the family Selenothemistidae Handlirsch, 1939: hindwing distal side (MAb) of discoidal cell about twice as long as basal side; unique shape of hindwing subdiscoidal cell, with AA making a right angle and with a broad cell below CuP in anal area; post- discoidal space not narrowed and RP3/4 not parallel to IR2 (Bechly, 1996). This family currently comprises the three gen- era Selenothemis Handlirsch, 1920 (Toarcian, Germany), Tur- anothemis Pritykina, 1968 (Oxfordian, Karatau, Kazakhstan), and Caraphlebia Carpenter, 1969 (early Middle Jurassic of Antarctica, after Towrow, 1967; Shen, 1994), and possibly Paraliassophlebia Hong, 1982 (Jiulongshan Formation, Middle Jurassic, North Hebei Province, China). Sinothemis n. gen. shares with Selenothemis the base of
RP2 not aligned with subnodus, unlike in Turanothemis, but Sinothemis has only one oblique vein ‘O’ as in Turanothemis, instead of two as in Selenothemis. Sinothemis also shares with Turanothemis the presence of only one crossvein below the pterostigma, unlike Selenothemis. Sinothemis differs from both Selenothemis and Turanothemis in the presence of only one row of cells between RP3/4 andMAa well distal (five cells) of nodus level, instead of zero to two as in these two genera; Sinothemis has only one row of cells between IR2 and RP3/4 well distal (three cells) of oblique vein, instead of zeor to one cell distal of ‘O’ as in Selenothemis and Turanothemis (Pritykina, 1968; Nel et al., 1993). The original description and figure of Caraphlebia were in great part reconstructed (Carpenter, 1969); Kelly and Nel (personal communication, 2018) revised this fossil that is rather poorly preserved. It strongly differs from Sinothemis, Selenothemis, and Turanothemis in having the bases of RP3/4 and IR2 very distant with four cells between them (an uncom- mon character in the Epiproctophora). Last, Paraliassophlebia could belong to the Selenothemistidae on the basis of the shape of the discoidal cell, but it differs from the other taxa in this family, including Sinothemis, in the subdiscoidal cell not greatly widened and AA not making a right angle, after Hong (1982). Sinothemis seems to be more closely related to Tur-
anothemis than to the other Selenothemistidae, supporting the similar ages of the two outcrops Karatau and Guancaishan. Both are the youngest representatives of the Selenothemistidae. It seems that this family became extinct during the latest Jurassic, while the closely related family Campterophlebiidae was still present and diverse in the Chinese Early Cretaceous (Li et al., 2012). The clade Isophlebioptera did not survive the great change in the odonatan fauna during the Cenomanian (Nel et al., 2010).
Acknowledgments
We sincerely thank two anonymous referees for their useful comments on the first version of the paper. This work was supported by the Ministry of Science and Technology (2016YFC0600406), the Strategic Priority Research Program of
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