Airapus lithuanicus Tamutis, Alekseev

Tamutis, Vytautas, Alekseev, Vitalii I. & Bukejs, Andris, 2017, A new species of Eupariini from Eocene Baltic amber (Coleoptera: Scarabaeidae: Aphodiinae), Zootaxa 4353 (3) : -

Airapus lithuanicus Tamutis, Alekseev , & Bukejs, new species

( Figs. 1–8 )

Type material. Holotype: “0001-01” [KZM], adult, complete, sex unknown. Ventral side of specimen almost completely obscured by “milky” opacity.

Paratype: “0001-02” [KZM], adult, complete, sex unknown. Elytra, pronotum, right mesotibiae and metatibiae, and tarsi visible in dorsal view; ventral part of specimen almost completely obscured by “milky” opacity.

Paratype: “0001-03” [KZM], adult, complete, sex unknown. Dorsal and ventral sides partially obscured by “milky” opacity; left side of dorsal surface visible; ventral view has anterior parts of protibiae and tarsi, ventral side of mesofemorae, and metathoracic legs visible.

Paratype: “0001-04” [KZM], adult, complete, sex unknown. Dorsal side of specimen partially and ventral side completely obscured by “milky” opacity; only left side of pronotum and basal part of elytra visible.

Paratype: “0001-05” [KZM], adult, complete, sex unknown. Dorsal side of specimen completely and ventral side partially obscured by ‘milky” opacity; only anterior part of head, both sides of prothorax (including episternum and epipleura), mesothorax and metathorax, ventral sides of legs, and medial part of abdomen visible in ventral view.

Paratype: “0001-06” [KZM], adult, complete, sex unknown. Dorsal side of specimen partially and ventral side completely obscured by “milky” opacity; only dorsal part of pronotum and most of elytra visible.

Paratype: “0001-07” [KZM], adult, complete, sex unknown. Dorsal and ventral sides completely obscured by “milky” opacity, but punctation and sculpture of medial part of pronotum and elytra clearly visible.

Paratype: “0001-08” [KZM], adult, complete, sex unknown. Dorsal side of specimen partially and ventral side completely obscured by “milky” opacity; only part of pronotum and medial part of elytra visible.

Paratype: “0001-09” [KZM], adult, complete, sex unknown. Dorsal and ventral sides almost without “milky” opacity, but position of specimen in amber piece renders most body regions incompletely visible, except for front of head, right side of pronotum, left mesothoracic and metathoracic legs.

Paratype: “3891” [CAG], adult, complete, sex unknown. Dorsal and ventral sides relatively clearly visible; only ventral part of head and prothorax slightly obscured by "milky" opacity.

Type strata. Baltic amber, mid-Eocene to Upper Eocene.

Type locality. Southeastern Baltic Sea coast.

Etymology. The specific epithet “ lithuanicus ” [Lithuanian] is toponymic adjective derived from the name of the Baltic country Lithuania.

Differential diagnosis. Airapus lithuanicus differs from Aphodiinae previously described from Baltic amber in possessing mesotibiae and metatibiae with longitudinal lines and two apical spurs, as well as possessing suite of characters mentioned in Table 1.

Within Airapus , the newly described fossil species differs from extant congeners ( Stebnicka & Howden 1996; Stebnicka 1998) in the combination of the following characters: sides of pronotum explanate, pronotal lateral margins crenulate and setose, pronotal base not bordered, pronotal posterior angles widely rounded, clypeal anterior margin slightly upturned and rounded on each side of anteromedial emargination, head finely and densely punctate, humeri with single small denticle, and head and pronotum without distinct setation.

Description. Habitus. Body moderately convex, elongate, almost parallel-sided; reddish brown to black in color, with lighter appendages (especially visible in paratype "0001-03"); apparently glabrous dorsally. Body length without head (head turned downwards) 3.4–4.0 mm, length with head about 4.1–4.8 mm, maximum width 1.5–2.0 mm. Holotype: “0001-01” 3.4 mm long without head (approximately 4.1 mm with head) and 1.7 mm wide; paratypes: “0001-02” 3.5 mm long (approximately 4.2 mm long with head), and 1.7 mm wide; “0001-03” 3.4 mm long (approximately 4.1 mm long with head), and 1.7 mm wide; “0001-04” 3.4 mm long (approximately 4.1 mm long with head), and 1.6 mm wide; “0001-05” 3.4 mm long (approximately 4.1 mm long with head), and 1.6 mm wide; “0001-06” 3.5 mm long (approximately 4.2 mm long with head), and 1.7 mm wide; “0001-07” 3.4 mm long (approximately 4.1 mm long with head), and 1.6 mm wide; “0001-08” 3.7 mm long (approximately 4.4 mm long with head), and 1.7 mm wide; “0001-09” 3.6 mm long (approximately 4.3 mm long with head), and 1.6 mm wide; “3891” 4.0 mm long (approximately 4.8 mm long with head), and 2.0 mm wide.

Head. Transverse, slightly convex, narrower than pronotal anterior margin; finely and densely covered with simple, round punctures, distance between punctures smaller than diameter of one puncture (punctures on vertex distinctly sparser). Clypeus dilated, covering mouthparts; anterior margin widely rounded toward obtuse angle on each side of shallow anteromedial emargination. Genae protruding, margin with few very short, stout setae. Compound eye moderately large and convex, visible in dorsal view. Maxillary palpus with 4 palpomeres; apical palpomere elongate, subcylindrical with narrowed apical half, 3.5× as long as wide, and about 2.7× as long as penultimate palpomere. Labial palpus with 3 palpomeres; short, minute; apical palpomere subcylindrical, slightly tapered, nearly as long as palpomeres 1–2 combined. Antennae with 3 antennomere club.

Thorax. Pronotum tranverse, 1.6× as wide as long; disc evenly and slightly convex, with lateral sides narrowly explanate and flat (width of flattened area reaches about 1/13 of pronotal width); densely covered with small punctures, with distance between punctures approximately 0.5–1.5× diameter of single puncture; punctures distinctly finer and sparser in anterior one-third of pronotal length. Lateral margins nearly straight, distinctly upturned, not bordered, without marginal line, crenulate; bearing sparse, scale-like, erect setae; posterior margin moderately convex, not bordered; anterior margin slightly convex. Anterior angles rounded, slightly protruding; posterior angles widely rounded.

Scutellum triangular (as long as anterior width), rounded apically.

Elytra parallel-sided, moderately convex, elongate, 1.4× as long as combined width, about 2.5× as long as pronotum, widest behind mid-length; elytral base narrower than pronotum; lateral margins bearing short, sparse setae. Humerus with single, small, sharp denticle. Each elytron apparent with 10 deep, punctate striae; punctures elongate (nearly twice as long as width); distance between punctures about 1.5–2.5× diameter of single puncture in basal one-third of elytra. Interstriae distinctly convex; granulate medially, granulation of interstriae 1–3 less distinct, granulation of interstriae 4–8 more conspicuous; and covered with fine, sparse secondary punctation. Epipleura wide at humeri and gradually narrowed toward elytral apex, reaching elytral apex.

Hypomeron finely, densely punctate. Mesosternum flattened, less elevated than metasternum; with convex triangular area above meso-metasternal suture, and top of triangle with very fine mesosternal carina. Mesosternum and mesocoxae finely and densely punctate (almost equal to prosternal punctation). Disc of metasternum almost flat with midline impressed; with sparse, moderately large punctures (distinctly larger than punctures of prosternum and mesosternum), distance between punctures 1–3× diameter of single puncture; lateral metasternal triangle broad, shallow, distinctly wrinkled. Procoxae and metacoxae apparently contiguous, mesocoxae widely separated by distance about equal to width of mesofemora. Mesocoxae subparallel-sided, flattened, with distinct longitudinal elevated line laterally; separated from base of elytral epipleuron by distinct mesepimeron.

Abdomen. With five visible ventrites, punctation similar to punctation of metasternal disc. Ventrites 2–3 equal in length; ventrite 4 slightly shorter, 0.6× as long as ventrite 3 medially; anterior margin of ventrite 4 slightly concave.

Legs. Protibia rather short, nearly as long as profemora, impunctate; with terminal spur, slightly arcuately downward; with three large, outer denticles in apical half and with few short, small denticles in basal half. Profemora wide, perimarginal groove deep, posterior margin with marginal line. Mesotibiae and metatibiae weakly expanded apically, with three longitudinal setigerous lines and punctures; with two terminal spurs of unequal length, longest spur distinctly shorter than tarsomere 1 and about 2× longer than shortest spur; apex of mesotibia and metatibia with fringe of spine-like accessory setae that are unequal in size. Mesofemora with sharp posterior marginal line, anterior margin arcuate; coarsely punctate with two distinct sizes of punctures (small punctures situated among large punctures), and punctures slightly larger than those of metasternum. Metafemora narrower, 1.3× as long as mesofemora, and covered with sparser punctation. Tarsal formula 5-5-5, slender, setigerous. Mesotarsi and metatarsi with basal tarsomere about as long as tarsomeres 1–4 combined. Claws fine, simple, symmetrical, acute.

Figures

FIGURES 1–2. Airapus lithuanicus new species: 1—habitus, dorsal view (left—holotype“0001-01” [KZM]; right—paratype “0001-02” [KZM]); 2 – habitus, ventral view (paratype “0001-05” [KZM]). Scale bars = 1 mm.

FIGURES 3–4. Airapus lithuanicus new species: 3—general view of amber piece “0001” [KZM] with specimen numeration (1—holotype; 2–9—paratypes); 4—habitus, frontal view (paratype “0001-09”). Scale bar: 5 mm for Fig. 3; 0.5 mm for Fig.4.

FIGURES 5–6. Airapus lithuanicus new species, paratype “3891” [CAG]: 5—habitus, dorsal view; 6—habitus, ventral view. Scale bars = 1 mm.

FIGURES 7–8. Airapus lithuanicus new species, paratype “3891” [CAG]: 7—details of forebody, ventral view; 8 —apical portion of elytra with setose lateral margin, dorsal view.Scale bar: 0.5 mm for Fig. 7; 0.25 mm for Fig. 8.