ANDRE NEL, DIDIER NERAUDEAU, VINCENT PERRICHOT, VINCENT GIRARD, and BERNARD GOMEZ
André Nel [firstname.lastname@example.org], CNRS UMR 5202, CP 50, Entomologie, Muséum National d’Histoire Naturelle, 45 rue Buffon, F−75005 Paris, France;
Didier Néraudeau [didier.neraudeau@univ−rennes1.fr], Vincent Girard [email@example.com−rennes1.fr], and Bernard Gomez [bernard.
gomez@univ−rennes1.fr], Géosciences Rennes, UMR CNRS 6118, Université Rennes 1, Campus de Beaulieu, bât.15, 263 Avenue du Général Leclerc, F−35042 Rennes cedex; Vincent Perrichot [firstname.lastname@example.org], Museum für Naturkunde der Humboldt−Universität zu Berlin, Invalidenstr. 43, D−10115 Berlin, Germany.
The new aeshnopteran family Enigmaeshnidae is proposed for Enigmaeshna deprei gen. et sp. nov., the first fossil insect collected as imprint in the Earliest Cenomanian clay of the Puy−Puy quarry at Tonnay−Charente (Charente−Maritime, SW France). The bed bearing E. deprei was previously known for its highly diversified fossil plant assemblage. Although this taxon belongs to the much derived clade Aeshnodea, it is char− acterized by several unique hind wing venation characters, never found in other Aeshnoptera, viz. part of MAb distal of the trigonal planate very long, and presence of five posterior branches of AA directed towards posterior wing margin.
◊ An open access article from Acta Palaeontol. Pol. 53 (1): 165-168, 2008, viewed from Biology-online.org.
The fossil dragonfly comes from the Puy−Puy quarry, at Tonnay−Charente (Charente−Maritime, SW France), about 20 km from the Charente river estuary (Fig. 1). In this quarry, the uppermost Albian−lowermost Cenomanian deposits are trans− gressive and erosive on the Kimmeridgian substratum. These deposits are mainly composed of fluvial and paralic sand, but contain several clay intercalations with local concentrations of plant compressions or lignite and amber (Néraudeau et al. 2005). Stratigraphically (Fig. 2), the clay level containing fossil arthropod imprints is located about seven metres under the first facies clearly dated as Early Cenomanian, a marine shelly sand (lithological sub−unit B1) containing dense accumulation of the large benthic foraminifera Orbitolina conica (Vullo et al. 2003). The clay level bearing the fossil Aeshnodea corresponds to the base of the sand and clay alternations (lithological sub−unit A2), underlying the shelly sand. Just a few decimeters underneath the fossiliferous clay there is 2–3 m thick fluvial azoic sand ar− ranged in large cross beddings (top of the sub−unit A1). The clay bearing arthropods and plants is devoid of sporomorphs and cannot be palaeontologically dated in this quarry (Peyrot et al. 2005). However, stratigraphical correlations with well−dated sections of other quarries from the same region (Néraudeau et al. 2002, in press), suggest an earliest Cenomanian age for the lithological sub−unit A2 from Puy−Puy.
The clay containing the fossil Aeshnodea corresponds to the basal part of the two main levels rich in plant compressions (P1, P2), as previously described by Gomez et al. (2004) and Nérau− deau et al. (2005). Apart from numerous fossil ferns, conifers and angiosperms, the level P1 delivered a few imprints of undeter− mined Blattodea and decapod crustaceans. The Aeshnodea im− print was fossilized at a clay surface at a few centimeters of an 80−cm−l3ong Dammarophyllum leaf (Coniferale: Araucariaceae or Podocarpaceae).
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).
Compared to the insect assemblages previously discovered in the Late Albian/Early Cenomanian ambers from the same re− gion (Charente−Maritime, SW France) (Néraudeau et al. 2002, 2003; Perrichot 2005), the outcrop of Puy−Puy appears original and exciting because it is the first that contains clay with insect imprints. Moreover, contrasting with the about 1000 specimens of arthropods found regionally in amber, it is the first time that an Odonata is recorded in the mid Cretaceous deposits from Charentes. It can be assumed that further analyses of the fossili− ferous clay of Puy−Puy will enrich the knowledge of the Albian– Cenomanian insects from France.
Other abbreviations.—AA anal vein; a.l., anal loop; AP anal posterior, A×0 A×1 A×2, primary antenodal cross−veins; CuAa, distal branch of cubitus anterior; CuAb, proximal branch of cubitus anterior; CuP, cubitus posterior; IR1 IR2, intercalary ra− dial veins; MA, distal branch of median anterior; MAb, poste− rior branch of median anterior; MP, median posterior; Mspl, me− dian supplementary; N, nodus; O, oblique vein; PsA, pseudo− anal vein; Pt, pterostigma; RA, radius anterior; RP, radius poste− rior; Rspl, radius supplementary; t.p., trigonal planate.
Acknowledgements.—The authors are greatly indebted to Eric Depré (Université Rennes 1, France) who discovered and donated the type specimen of Odonata to the MNHN, the family of Patrick Chauvet, owners of the Puy−Puy quarry, and Pierre Bénéfice (St. Pierre d'Oléron, France), first collector of fossil plants, who greatly helped us in our re− searches. We must also thank colleagues, especially Romain Vullo (Université Rennes 1, France), and students that helped us to collect samples during field excavations since 2002. The Research of A.N. was financially supported by CNRS UMR 5202 and Muséum national d’Histoire naturelle, and of D.N., M.L., V.G., and B.G. by UMR 6118 CNRS from Rennes. This article is a contribution to the CNRS ANR program “AMBRACE” (project nBLAN07−1−184190). A.N. and B.G. were also granted by projects CGL2005−00046/BTE and CGL2005− 01121 of the Ministerio de Educación y Ciencia of the Spanish Govern− ment, and VP by a research fellowship of the Alexander von Humboldt Foundation. We sincerely thank our colleagues Frank L. Carle (Univer− sity of New Jersey, USA) and Günter Bechly (Staatliches Museum für Naturkunde Stuttgart, Germany) for their useful and kind review of this paper.
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Figure 1 Map of the Tonnay-Charente area (SW France) with location of the Puy-Puy quarry with Early Cenomanian deposits (A) and geological section (B)with the position of the studied sample with fossil Odonata (arrow). A1, fluvial sand with large cross beddings; A2, estuarine alternation of sand and clay, with three main fossiliferous levels (P1, plant compressions and arthropod imprints; P2, plant compressions only; GB, arthropods tracks); B1, marine shelly sand.
Figure 2 Anisopteran Enigmaeshna deprei gen. et sp. nov. from Early Cenomanian of the Puy-Puy quarry (Tonnay-Charente, SW France). Holotype MNHN-LP-R 63889, photomicrograph (A) and explanatory drawing (B). Abbreviations: a.l., anal loop; A×1, A×2, primary antenodal cross-veins; CuAa, distal branch of cubitus anterior; CuP, cubitus posterior; IR2, intercalary radial vein; MA, median anterior; MP, median posterior; N, nodus; Pt, pterostigma; RP2, RP3/4, radius posterior; t.p., trigonal planate.