In the description below we follow the wing venation nomencla− ture of Riek and Kukalová−Peck (1984), amended by Kukalová− Peck (1991), Nel et al. (1993), and Bechly (1996). The higher classification of fossil and extant Odonatoptera, as well as familial and generic characters followed in the present work, are based on the phylogenetic system proposed by Bechly (1996) and Bechly et al. (2001) for the Mesozoic Aeshnoptera.
Suborder Anisoptera Selys, 1854
Clade Aeshnoptera Bechly, 1996
Family Enigmaeshnidae nov.
Type genus: Enigmaeshna gen. nov., by monotypy.
Diagnosis.—Hind wing characters only. Discoidal triangle di− vided into numerous cells, very elongate; part of MAb distal of the trigonal planate very long (autapomorphy); trigonal planate very strong and long (apomorphy); a long and straight pseudo− ScP distal of nodus (autapomorphy); submedian area and sub− discoidal space crossed by five cross−veins, with CuP and PsA not stronger than others; anal area very long, with five posterior branches of AA directed towards posterior wing margin (autapomorphy); anal loop broad, elongate, sub−rectangular, posteriorly closed, divided into numerous cells; one row of cells in area between MP and CuAa distal of discoidal triangle. Genus Enigmaeshna nov.
Type species: Enigmaeshna deprei sp. nov.
Derivation of the name: Referred to genus Aeshna and the enigmatic po− sition among Aeshnoptera.
Diagnosis.—As for the family.
Enigmaeshna deprei sp. nov.
Derivation of the name: After Eric Depré, who discovered the type specimen.
Holotype: MNHN−LP−R 63889, Eric Depré coll., imprint [female].
Type locality: Puy−Puy quarry, Tonnay−Charente, Charente−Maritime, France.
Type horizon: Late Cretaceous, Earliest Cenomanian, lithological sub−unit A2 (level P1 sensu Néraudeau et al. 2005).
Diagnosis.—As for the family.
Description.—Print of basal half of a female hind wing, 29.6 mm long, wing 14.7 mm wide; distance from base to arculus 6.8 mm; from arculus to nodus 15.8 mm; from arculus to base of RP3/4 10.1 mm; no secondary antenodal cross−vein basal of A×1, six antenodal cross−veins of first row and five of second row between A×1 and A×2, 12 of first row and 9–10 of second row distal of A×2; distance from wing base to A×1 5.0 mm, be− tween A×1 and A×2 6.1 mm; A×2 well distal of base of disco− idal triangle; RP and MA strongly separated in arculus; hyper− triangle 8.1 mm long, with seven cross−veins; discoidal triangle 1.8 mm distal of arculus, divided into eight smaller cells, very elongate and rather narrow, with basal side 2.3 mm long, ante− rior side 6.2 mm long, and MAb 5.7 mm long; a distinct angle in MAb at base of convex trigonal planate; part of MAb distal of trigonal planate very long, 2.5 mm long; postdiscoidal area with three rows of cells; a strong convex trigonal planate, long and nearly straight; only basal part of Mspl present, thus it is not pos− sible to determine if it was well defined; a long and straight pseudo−ScP distal of nodus, four cells and 4.3 mm long; basal part of area between RA and RP with only five cross−veins basal of RP3/4, and five distal of base of RP3/4 and basal of subnodus; area between RP and MA with five cross−veins basal of RP3/4; one visible oblique vein “O” one cell distal of base of RP2; two rows of cells between IR2 and RP3/4 two cells distal of sub− nodus; one row of cells between MP and CuAa, with a strong narrowing of area between these veins opposite base of RP3/4; median area free; submedian area and subdiscoidal space cros− sed by five cross−veins, with CuP and PsA not stronger than oth− ers; posterior wing margin rounded at base (female specimen); anal area very long but not very broad, with five posterior branches of AA directed towards posterior wing margin, and 8–9 rows of cells between AA and posterior wing margin; anal loop rather broad, elongate, sub−rectangular, posteriorly closed, divided into nine cells; cubito−anal area broad, with 9–10 rows of cells between CuAa and posterior wing margin; CuAa with six posterior branches.
Discussion.—The very long discoidal triangle of this hind wing suggests affinities with the Aeshnoptera. The presence of a very strong convex trigonal planate is a specialized character con− vergently present in the gomphid genus Hagenius Selys, 1854 (and related taxa), the Mesozoic aeshnopteran family Liupan− shaniidae Bechly, Nel, Martínez−Delclbs, Jarzembowski, Co− ram, Martill, Fleck, Escuillié, Wisshak, and Maisch, 2001 and the clade Neoaeshnida Bechly, 1996 (Bechly et al. 2001; Lin et al. 2002). However Enigmaeshna gen. nov. has not the main synapomorphies of the Liupanshaniidae, i.e., in hind wing, ante− rior side of discoidal triangle curved, and MAb strongly angular and sigmoidally curved. Furthermore, Enigmaeshna has a series of parallel cross−veins in its subdiscoidal space plus subdisco− idal triangle, including a weakened vein PsA of the same strength as other cross−veins, which is a character only present in the most advanced group Aeshnodea Bechly, 1996. However, within this clade, some taxa like Brachytron Evans, 1845 have retained a strong PsA. This character is sufficient to exclude af− finities with the Liupanshaniidae and the Gomphaeschnidae, sister group of the Aeshnodea.
The presence of several accessory cubito−anal cross−veins is a potential synapomorphy of the Aeshnoidea Leach, 1815 (sensu Bechly 1996), and the presence of more than two rows of cells in the basal part of the postdiscoidal area would support affinities with the Aeshnidae Leach, 1815 (sensu Bechly 1996). Unfortu− nately, the lack of information on the structures of the distal half of this wing (Rspl, distal part of RP2, IR2, RP3/4, MA, Mspl, pterostigma), and the lack of the forewing impede us to be more precise on its affinities within the Aeshnodea. Nevertheless, Enigmaeshna differs from all the known Aeshnoptera in very im− portant structures that allow us to consider that it does not belong to any of the known subclades of this group, viz. part ofMAb dis− tal of the base of the trigonal planate very long (more than length of three cells instead of 1–2 in other Aeshnoptera), and anal area very elongate with five posterior branches of AA basal of the anal loop. A further specialized character is the presence of a pseudo− ScP distal of the nodus, but it is also present in some Recent and Cenozoic Aeshnidae (Aeschnophlebia Selys, 1883).