Siphloplecton sartorii, Staniczek, Arnold H. & Godunko, Roman J., 2016

Staniczek, Arnold H. & Godunko, Roman J., 2016, Revision of fossil Metretopodidae (Insecta: Ephemeroptera) in Baltic amber — Part 3: Description of two new species of Siphloplecton Clemens, 1915, with notes on the re-discovered lectotype of Siphloplecton macrops (Pictet-Baraban & Hagen, 1856), Zootaxa 4103 (1), pp. 1-24 : 17-20

Siphloplecton sartorii sp. nov.

Figures 10 A–H, 11A–B

Material. Holotype. Male imago in Baltic amber (Eocene), CCHH, BaB-1177/3.

Well preserved specimen in clear amber, well visible in lateral aspect, especially from left side. Distal parts of forewings lost; left hind wing damaged distally; right hind wing preserved, but very twisted. Legs almost entirely preserved, except of distal tarsal segments of forelegs and right middle leg. Small amount of “Verlumung” on dorsal and lateral sides of thorax near wing bases, and partly on abdominal terga. Cerci only partly preserved.

For measurements see Table 5.

Etymology. Following our tradition of naming new fossil species of Siphloplecton after Swiss ephemeropterists, this species is named after Michel Sartori, Lausanne, to honor his numerous contributions to the knowledge of mayflies.

Description. General coloration of body pale, yellow to light brown; thorax dark brown ( Fig. 10 A). Irregular pigmentation on surface of thorax and abdomen. Head uniformly light brown. Eyes large, medially contiguous; visible parts of eyes uniformly colored, without pigmented fields ( Fig. 10 B). Ocelli and antennae completely preserved, yellowish-brown, slightly darker near bases.

Thorax with traces of irregular, dirty brown pigmentation; prothorax brown; mesonotal suture slightly bulged medially, not transverse; lateroparapsidal suture distinctly elongated, without surrounding pigmentation, covered only with artificial spots ( Figs 10 B, 11A); ventral side of thorax poorly visible; mesothorax with fused furcasternal protuberances.

Wings translucent, hyaline, not pigmented, only with several small dark spots (mainly basally), pterostigmatic area predominantly lost in both forewings, preserved parts with several anastomosed veins ( Fig. 10 C). Cubital field of forewings well visible, with two pairs of interconnected intercalaries, respectively also connected with CuA and CuP ( Figs 10 C, E, F). Hind wings with triads RS, MA and MP, costal process bluntly pointed and small ( Fig. 10 D).

Legs yellowish to light brown. Foretibia with several sharply pointed setae along outer margin; forefemur paler than tibia and preserved part of tarsus. Apical tarsal segments of middle and hind legs slightly darker than tibia and femora; tibia of middle and hind legs with traces of tibiopatellar suture; first tarsal segments of middle and hind legs fused with tibia ( Fig. 10 G). Tarsal claws dissimilar, with one rounded and one hooked claw.

Abdomen completely preserved, uniformly light brown, with irregular darker maculation.

Styliger plate angulate, deeply incised mediocaudally with prominent lateral projections; medial projection small, pointed apically ( Figs 10 H, 11B). Basal segment of forceps narrow and elongated, with apical hump on inner side; forceps 4-segmented, segment 4 approximately 3.38 times longer than wide; length ratio of segment 3 to segment 4 approximately 1.2: 1. Penis lobes large, well separated apically by a wide V-shaped cleft; medial sclerite rounded apically, well separated from lateral sclerite on outer margin; lateral sclerites broad and prominent; apical sclerite relatively broad ( Figs 10 H, 11B).

Paracercus vestigial, 5-segmented; cerci partly lost.

Discussion. We attribute this new species to the S. picteti species group based on (1) two pairs of intercalary veins in cubital field of forewing, (2) stout pointed spines on outer margin of foretibia, and (3) shape of genitalia. The new species differs from the closely related S. picteti by (1) slim and elongated basal segment of forceps (in contrast to nearly square segment in S. picteti ); (2) segment 4 of forceps clearly elongated, with length/width ratio—3.38 (in contrast to less elongated segment 4 in S. picieti with length/width ratio—2.58−2.72); (3) forceps segment 3 slightly longer than segment 4 (in contrast to S. picteti with segments 3 and 4 of about same length); (4) penis lobes well separated apically (in contrast to nearly fused lobes in S. picteti ); (5) lateral sclerites of penis lobes distinctly broad and prominent laterally (in contrast to more slender lateral sclerite in S. picteti ). Some differences between both species also concern size of body, legs and wings.

Figures

FIGURE 10. Siphloplecton sartorii sp. nov., CCHH, BaB 1177 / 3, holotype, male imago (photographs): A—total dorsolateral view; B—head and thorax dorsolaterally; C—right forewing in dorsal view; D—left hind wing; E—cubital field of right forewing in dorsal view; F—cubital field of left forewing in dorsal view; G—left hind leg in lateral view; H—genitalia in ventral view.