Siphloplecton landolti, Godunko, Roman J., Neumann, Christian & Staniczek, Arnold H., 2019

Godunko, Roman J., Neumann, Christian & Staniczek, Arnold H., 2019, Revision of fossil Metretopodidae (Insecta, Ephemeroptera) in Baltic amber - Part 4: Description of two new species of Siphloplecton Clemens, 1915, with notes on the new S. jaegeri species group and with key to fossil male adults of Siphloplecton, ZooKeys 898, pp. 1-26 : 1

Siphloplecton landolti sp. nov. Figures 5 , 6 , 7 ; Table 1

Material examined.

Holotype. Male imago in Baltic amber (Eocene), SMNS BB– 2377. Well preserved specimen in clear amber, well visible in dorsoventral aspect. Each of both forewings bent upwards approximately at half length (left forewing partly twisted); left hind wing twisted; genitalia visible in ventral and, partly, lateral view.

For measurements see Table 1 .

Description.

Colouration pale, dorsal side slightly darker than ventral side. Brownish diffuse maculation on thorax and abdomen preserved. Ocelli well preserved. Eyes large, medially contiguous; brownish maculation on eye surface partly preserved; antennae longer than head ( Figs 5 A–C, E , 6 A–B ).

Thorax with traces of brownish pigmentation on dorsal and ventral sides; “Verlumung” mainly on lateral sides near wing bases. Lateroparapsidal suture elongate, typical for Siphloplecton ; no conspecific pigmentation around lateroparapsidal suture; mesonotal suture medially bulged ( Fig. 6A ); furcasternal protuberances of mesothorax contiguous ( Fig. 6B ); lateral aspect of thorax hardly visible.

Wings translucent, hyaline, not pigmented, venation well visible; pterostigma translucent, without pigmentation, with simple veins. Cubital field of forewing well visible on right wing only (twisted on left wing): one distinct pair of intercalary veins (iCu2 and iCu3) situated close to CuP and connected with CuP and CuA; one long intercalary vein (iCu1) connected with CuA and also with iCu2 by crossveins; additional short intercalaries present, ending at hind margin of wing (one of them between iCu1 and iCu2, basally joining both veins) ( Fig. 5C ). Hind wings with triads RS, MA and MP, 0.31 × forewing length; costal process bluntly pointed ( Fig. 5D ).

Legs damaged; both right fore- and hind legs lost; tarsus of left foreleg only partly preserved (for details see Table 1 ). Tibia of left foreleg paler than femur and tarsus. Left foretibia with strong, sharply pointed setae along outer margin. Tibia of left middle and hind legs black; preserved part of first tarsomere of left middle leg black. Tibia of middle and hind legs with trace of tibiopatellar suture; first tarsomere of middle and hind legs fused with tibia. Tarsal claws lost ( Fig. 5 A–B ).

Abdominal segments completely preserved, sterna visibly paler than terga; genitalia dark.

Styliger plate angulate, mediocaudally deeply incised; these incisions with pronounced, broad, triangular projections; medial projection not large, blunt apically ( Figs 5F , 7 ). Basal segment of forceps basally relatively wide; forceps 4-segmented, segment 4 approximately 3.30 times longer than wide; length ratio of segment 3 to segment 4 approximately 1:1. Penis lobes distinctly elongated, well separated from each other apically, ellipsoidal; medial sclerite rounded apically; lateral and medial sclerite markedly separated on outer side with inconspicuous incision between sclerites; features of ventral surface of penis lobes not visible ( Figs 5F , 7 ).

Paracercus vestigial; cerci partly lost.

Comments.

The new species can be placed within the jaegeri species group based on the characteristic shape of the penis lobes, the arrangement of cubital intercalaries of the forewing and the sharply pointed setae along the outer margin of the foretibia. Siphloplecton landolti sp. nov. can be separated from the closely related S. jaegeri by (1) shape of styliger with relatively small and apically rounded medial projection; (2) relatively wide base of basal forceps segment compared to adjoining apical part of plate; (3) proportions of last forceps segments; (4) ellipsoidal shape of penis lobes with medial sclerite rounded at tip.

The body measurements of S. landolti sp. nov. are comparable to other representatives of the S. jaegeri species group, but the ratio of hind/forewing length is lower in comparison with S. jaegeri itself.

Etymology.

Following our tradition of naming new fossil species of Siphloplecton after Swiss ephemeropterists, this species is named after Peter Landolt, Lausanne, to honour his contributions to the knowledge of Swiss mayflies.

Figures

Figure 5. Siphloplecton landolti sp. nov., SMNS, BB- 2377, holotype, male imago (photographs) A general dorsal view B general ventral view C cubital field of right forewing D right hind wing in dorsal view E head and thorax in ventral view F genitalia in ventral view.

Figure 6. Siphloplecton landolti sp. nov., SMNS, BB- 2377, holotype, male imago (line drawings) A head and thorax in dorsal view B head and thorax in ventral view.

Figure 7. Siphloplecton landolti sp. nov., SMNS, BB- 2377, holotype, male imago (line drawing): genitalia in ventral view.