Petrolestes messelensis, Garrouste, Romain & Nel, André, 2015

Garrouste, Romain & Nel, André, 2015, New Eocene damselflies and first Cenozoic damsel-dragonfly of the isophlebiopteran lineage (Insecta: Odonata), Zootaxa 4028 (3), pp. 354-366 : 359

Petrolestes messelensis sp. nov.

( Figs. 6–7 )

Material. Holotype specimen MeI 11777 (the distal two-third of a wing), SMF.

Age and outcrop. Lower Middle Eocene, Geiseltalian (Lower Lutetian), ca. 47 million year old former Maar lake Messel, near Darmstadt, Hesse, Germany.

Diagnosis. Wing characters only. Intercalaries between MA and MP very short and only present close to posterior wing margin; 15 postnodals; wing rather small, 5.4 mm wide at nodus level.

Etymology. Named after the Messel Formation.

Description. Wing hyaline in its preserved part; fragment 17.8 mm long, 5.4 mm wide at nodus; distance from nodus to pterostigma ca. 10.4 mm; pterostigma long and broad, 1.8 mm long, 0.8 mm wide, covering ca. four-six cells; pterostigmal brace not oblique; no supplementary antenodal crossvein of first row or second row in preserved part of antenodal space; ScP not crossing through nodus as in Stenolestes Scudder, 1895; nodal crossvein oblique; subnodus nearly vertical with crossvein between RP 1/2 and IR2 below it of inverted obliquity; 15 postnodal crossveins preserved, not aligned with the 14 postsubnodal crossveins; bases of RP 3/4 and IR2 between arculus and nodus, probably closer to arculus than to nodus ( RP 3/4 and IR2 are basally ‘mixed’ due to taphonomic deformation); base of RP 2 three cells distal of subnodus; base of IR1 four cells distally; oblique crossvein ‘O’ absent; cubito-anal area with four-five rows of cells between CuA and posterior wing margin; CuA reaching posterior wing margin well distal of nodus level; CuA weakly curved; area between MP and posterior wing margin moderately broad; postdiscoidal area not widened distally, with very short secondary longitudinal vein between MP and MA near posterior wing margin; area between RP 3/4 and MA with three secondary longitudinal veins in between; four rows of cells between RP 3/4 and IR2, two rows between RP 1 and IR1; three rows of cells between IR1 and RP 2 opposite pterostigma, but only one basally.

Discussion. Although incompletely preserved, this wing is very similar to that of the new specimen of Petrolestes hendersoni , especially in the long pterostigma, with brace not oblique, bases of RP 3/4 and IR2 well basal of subnodus, absence of oblique vein ‘O’, organisation of the intercalaries between main veins, position of the bases of RP 3/4 and IR2, shape of the subnodus and of the crossveins situated below it. Thus this new fossil can be accurately attributed to the genus Petrolestes. It differs from P. hendersoni in few characters, viz. the intercalaries between MA and MP are very short only present close to the posterior wing margin instead of being present just distal of nodus level; and 15 postnodals instead of 17; wing distinctly smaller as its width at nodus is 5.4 mm instead of 8.0– 8.1 mm for P. hendersoni .

Figures

FIGURE 6. Petrolestes messelensis sp. nov., holotype MeI 11777, photograph of habitus. Scale bar represents 5.0 mm.

FIGURE 7. Petrolestes messelensis sp. nov., holotype MeI 11777, drawing of wing. Scale bar represents 5.0 mm.