Ecdyonurus (Nestormeus) groehnorum, Godunko, Roman J., 2007

Godunko, Roman J., 2007, Contribution to the knowledge of the fossil subgenus Nestormeus Godunko, 2004 (Ephemeroptera: Heptageniidae: Ecdyonurus) from the Baltic amber (Eocene), Zootaxa 1661, pp. 63-68 : 63-68

Ecdyonurus (Nestormeus) groehnorum sp. nov.

( Figs 1–6 )

Description. Female imago. Measurements: see Table 1.

Characters (mm) Length of body 5.33

Length of right fore leg 3.95

Length of femur 1.53

Length of tibia 1.38

Length of tarsus 1.04

Segment I 0.15

Segment II 0.28

Segment III 0.25

Segment IV 0.18

Segment V 0.18

Length of left fore leg 3.86

Length of femur 1.50

Length of tibia 1.40

Length of tarsus 0.96

Segment I 0.15

Segment II 0.28

Segment III 0.23

Segment IV 0.15

Segment V 0.15

Length of right middle leg 3.52

Length of femur 1.63

Length of tibia 1.23

Length of tarsus 0.66

Segment I 0.13

Segment II 0.15

Segment III 0.13

Segment IV 0.10

Segment V 0.15

Length of left middle leg 3.50

Length of femur 1.58

Length of tibia 1.28

Length of tarsus 0.64

Segment I 0.13

Segment II 0.13

Segment III 0.13

Segment IV 0.10

Segment V 0.15

Length of right hind leg 3.20

Length of femur 1.58

Length of tibia 1.05

to be continued.

Characters (mm) Length of tarsus 0.57 Segment I 0.13 Segment II 0.13 Segment III 0.10 Segment IV 0.08 Segment V 0.13 Length of right fore wing 5.93 Length of left fore wing 5.75 Length of right hind wing -

Length of left hind wing 2.13 Hind /fore wings length ratio 0.36 Length of cerci 8.00*

*Completely preserved right cercus only. Left cercus damaged, the length of preserved part is 2.4 mm.

Body pale. Head uniformly brownish pigmented. Eyes noncontiguous, widely separated.

Thorax light brown to brown with paler pronotum. Some brownish smudges around mesonotal sutures. Ventral side of thorax with the same color as dorsal one. Mesonotal suture deep, well visible, stretched backward medially. Medioparapsidal suture is well visible from the left side of the body only. Lateroparapsidal sutures deep and slightly curved, noncontiguous with medioparapsidal sutures ( Fig. 1 ). Proximal part of mesonotum invisible from dorsal view. Median impression of furcasternum of mesothorax with sub-parallel margins, narrowed posteriorly and distinctly divergent in anterior part. Prosternum without any transversal ridge, typical of Ecdyonurus s. l. ( Fig. 2 , 5 ).

Both pairs of wings translucent and opaque ( Fig. 6 ). Cubital field of fore wings with two pairs of intercalary veins. Hind wings with RS, MA and MP triads. Hind right wing damaged. Wing venation well preserved, with typical structure of the family Heptageniidae (see Kluge 2004: 380–384). Patella-tibial suture is distinct enough in middle and hind legs. Tarsi of all legs are 5-segmented, with dissimilar tarsal claws (one pointed and one blunt claw).

Abdominal segments slightly deformed. Abdominal terga and sterna paler than thorax. Subgenital plate large, well developed, with visible apically impression. Subanal plate elongate, rounded, apically with marked tip ( Figs 3 , 4 ). Cerci preserved, longer than body (see Table 1).

Affinities. Ecdyonurus groehnorum sp. nov. belongs to the subgenus Nestormeus within the genus Ecdyonurus , which can be distinguished from the other representatives of this genus by the combination of the following characters: (1) median impression of furcasternum of mesothorax with sub-parallel margins, narrowed posteriorly and distinctly divergent in its anterior part (see Kluge 2004), and (2) lateroparapsidal sutures deep and slightly curved, noncontiguous with medioparapsidal sutures (see Godunko 2004).

The new species can be easily distinguished from the earlier described E. leopoliensis by the shape of the subanal and (especially) the subgenital plates. In contrast to E. leopoliensis , which can be characterized by the presence of a rounded apically subgenital plate without any impression, E. groehnorum sp. nov. bears a visible impression on the tip of the subgenital plate. The subanal plate of the new species is elongate with the tip marked apically, in contrast to the short and uniformly rounded subanal plate of E. leopoliensis . Other characters of the holotype of E. groehnorum , i.e. body measurements and general aspects of coloration, are close to E. leopoliensis .

In the previous publication on the subgenus Nestormeus , the prothorax structure has not been described, because the anterior part of the type specimen of E. leopoliensis is invisible in ventral view ( Godunko 2004: 326, Fig. 2 ). Thus, the examination of the prothorax peculiarities in E. groehnorum sp. nov. may contribute to the diagnosis of this fossil subgenus, showing the presences of the prosternum without a transversal ridge (typical of Ecdyonurus s. l., see Kluge 2004).

Type. Holotype: female imago in the Baltic amber (Eocene), with well preserved body, being well visible from ventral view, and partly from dorsal and lateral views. The holotype is housed in the collection of the Geological-Palaeontological Museum, University of Hamburg ( Germany), S.G.P.I.H. no. 4451 (ex coll. Carsten Gröhn no. 76).

Etymology. The new species is named in honor of Jutta and Carsten Gröhn with hearty gratitude for supporting my stay in Hamburg.

Figures

FIGURES 1 – 3. Ecdyonurus (Nestormeus) groehnorum sp. nov., holotype, female imago: 1, head and thorax laterally and dorsally; 2, body ventrally; 3, tip of abdomen ventrally; 1 – 2: scale bars = 1 mm; 3: scale bar = 0.5 mm.

FIGURES 4 – 6. Ecdyonurus (Nestormeus) groehnorum sp. nov., holotype, female imago: 4, tip of abdomen ventrally; 5, mesothorax ventrally; 6, body ventrally.