Rhabdomastix ( Rhabdomastix ) setosa, Jordan-Stasiło & Kania-Kłosok & Krzemiński, 2025

Rhabdomastix ( Rhabdomastix) setosa sp. nov.

Figs. 3 View Fig , 4.

ZooBank LSID:lsid:zoobank.org:act: E6B70F17-F77B-40DE-B319-13 B9E8DCA87E

Etymology: From Latin saetae, setaceous, bristly. Adjective.

Holotype: SDEI CCHH 1462-2 , male, specimen well preserved, only some of the legs are not preserved (coll. Ch. and H.W. Hoffeins).

Type locality: Baltic area, the Blue Earth (Blaue Erde).

Type horizon: Secondary deposit found mainly in glauconitic marine sediments of middle Eocene age (Lutetian Stage; 47.8–41.3 Ma), deposited along the paleo-North Sea margin ( Wolfe et al. 2016).

Material.—ISEA PAS MP/3472, male, specimen very poorly preserved; ISEA PAS MP/3945, male, specimen poorly preserved, only the wing and antennae were well visible; SDEI CCHH 1471-2, male, specimen well preserved, only some of the legs are not preserved; all from Baltic amber, Lutetian, middle Eocene, 47.9–41.3 Ma.

Diagnosis.—Antennae elongate, thin, longer than body by about 0.3 times of its length, longer than wing, without color pattern; flagellomeres elongate, first flagellomere almost 5 times as long as wide, flagellomeres 2–10, 7 times as long as wide, flagellomeres 11–13, 5 times as long as wide, last flagellomere half length of penultimate one; long setae on flagellomeres elongate, only slightly shorter than length of segments bearing them; tip of Sc beyond half length of wing, opposite 0.6 times of Rs; Rs shorter than R 2+3+4 and R 4 combined, by about 0.3 times of its length; R 1 ends beyond half length of d-cell, opposite approximately 0.6 times of R 2+3+4; R 4 4 times as long as R 3, R 4 longer than R 2+3+4; distance between tips of R 1 and R 3 longer than R 3; M 3 2 times longer than d-cell, m-cu situated beyond half length of d-cell, at level of approximately 0.6 times of d-cell length; d-cell 2 times as long as wide, narrow at base, widened in distal part; anal angle unexpanded; distance between tips of A 1 and A 2 2.5 times longer than distance between tips of Cu and A 1; tip of A 2 before Rb bifurcation; tip of A 1 before Rs fork; outher gonostylus elongate, narrow, only slightly longer than inner gonostylus; haltere arrange less than 0.25 times of wing length.

Description.— Body: 3.12–3.36 mm long, dark brown ( Fig. 3A View Fig 1 View Fig ), wing without color pattern, pterostigma absent, haltere slightly elongate ( Fig. 3A View Fig 2 View Fig ).

Head: 0.24 mm wide ( Fig. 3A View Fig 1 View Fig ); antennae elongate ( Figs. 3A View Fig 1 View Fig , A 6 View Fig , 4A 4) scape narrower at the base, slightly widened distal; padicel 2 times as long as wide, in the middle of the pedicel there are single, relatively short setae; flagellomeres very narrow, thin, elongate. Antenna 3.61–4.23 mm long: scape 0.09–0.10 mm long; pedicel 0.10 mm long; flagellomeres: 1, 0.14–0.21 mm; 2, 0.27–0.32 mm; 3, 0.28–0.32 mm; 4, 0.28– 0.34 mm; 5, 0.28–0.34 mm; 6, 0.28–0.34 mm; 7, 0.28–0.35 mm; 8, 0.28–0.37 mm; 9, 0.28–0.36 mm; 10, 0.26–0.32 mm; 11, 0.25–0.28 mm; 12, 0.25–0.26 mm; 13, 0.22– 0.17 mm; 14, 0.05–0.07 mm. Palpus ( Figs. 3A View Fig 1 View Fig , A 5 View Fig , 4A 2 View Fig ) 0.32–0.47 mm long (1, 0.05–0.11 mm; 2, 0.08 mm; 3, 0.08–0.11 mm; 4, 0.11–0.17 mm); palpomeres elongate; the last palpomere 2 times as long as penultimate one, 6 times as long as wide, other palpomeres 2 times as long as wide; on each palpomeres several setae of varying length, 1.5– 3 times longer than the width of the segment on which they occur.

Thorax: Wing 3.23–3.50 mm long, 0.79–0.91 mm wide, 3.5 times as long as wide ( Figs. 3A View Fig 1 View Fig , A 7 View Fig , 4A 1 View Fig ); crossvein (h) positioned at 0.2 times the length of the wing from its base; crossvein sc-r terminating 2 times its own length from the tip of Sc; the distance between tips of Sc and R 1 2.5 times longer than the tips of R 1 and R 3; M 1+2 over 2 times longer than d-cell; M 4 short, slightly longer than d-cell; Mb 3 times as long as M 3; Cu from the point of connection with crossvein m-cu to the edge of wing straight; A 1 slightly bent at the edge of the wing; A 2 sinusoidal. The distance between the tips of M 1+2 and M 3 shorter than the distance between the tips of M 3 and M 4; the distance between the tips of M 3 and M 4 and the tips of M 4 and Cu, and the distance between the tips of M 4 and Cu and also the tips of Cu and A 1 comparable; the distance between the tips of A 1 and A 2 slightly longer than the distance between the tips of M 4 and A 1; A 1 almost straight, A 2 slightly sinusoidal.

Haltere: 0.48–0.53 mm long, sterm long, narrow 2 times as long as knob ( Fig. 3A View Fig 2 View Fig ).

Hypopygium: elongate, 0.63 mm long, gonocoxites very elongate, rather narrow, outer gonostylus elongate, narrow, inner gonostylus slightly widened at the base, narrowed distally, numerous setae on the outer and inner gonostylus ( Figs. 3A View Fig 1 View Fig , A 3 –A View Fig 5 View Fig , 4A 3 View Fig ).

A1 R ₃ R ₁ Sc sc-r Rs R ₄ C h Mb R ₅ d A 3 outer gonostylus M₁+₂ m-cu M₃ M₄ 500 µm Cu A₁ A 2 II inner gonostylus A₂ gonocoxite I A4 1 mm III IV 250 µm 250 µm tergite IX scape

pedicel

Remarks.—The features which allow to include the species within the subgenus Rhabdomastix are: elongate antennae, longer than body length, crossvein well developed, d-cell hexagonal, distal part of M 1+2 and M 3 arched, outer gonostylus longer than inner gonostylus.

The antennae in Rhabdomastix ( R.) setosa sp. nov. are longer than the body length. Antennae longer than the body length also occur in the following species: Rhabdomastix R.) grussica Podenas, 2006 comb. nov., Rhabdomastix ( R.) mastix Podenas, 2006 comb. nov., Rhabdomastix ( R.) rafali sp. nov., Rhabdomastix ( R.) setix Podenas, 2006 comb. nov., and Rhabdomastix ( R.) woottoni sp. nov. In other species known from Cenozoic resins, belonging to the subgenus Rhabdomastix , the antennae are shorter than the body length. In R. ( R.) woottoni sp. nov. antennae are 1.5 times as long as the body and are very narrow, flagellomeres are very elongete with numerous, short setae. In R. ( R.) setosa sp. nov. antenna are not so elongate, flagellomeres are much shorter than their length, only 7 times as long as wide. The setae on each flagellomere are much longer and more dense. Moreover, the R. ( R.) setosa sp. nov. differs from other Cenozoic species within the subgenus Rhabdomastix in its wing venation and morphology of the hypopygium. Unlike the R. ( R.) grussica Podenas, 2006 comb. nov., setae occur on the antennae constitute even more than half the length of the segment bearing them, in R. ( R.) grussica Podenas, 2006 comb. nov. they are never longer than half the length of the flagellomeres bearing them. The d-cell in R. ( R.) setosa sp. nov. is small, 1.5 times as long as wide, vein M 3 is 2 times as long as the d-cell. In R. ( R.) grussica Podenas, 2006 comb. nov. d-cell is 2 times as long as wide, vein M 3 is only slightly longer (1.5 times). In R. ( R.) mastix Podenas, 2006 comb. nov. the setae are shorter than half the length of the flagellomeres on which they occur, d-cell is 2 times as long as wide. Vein Sc in R. ( R.) mastix Podenas, 2006 comb. nov. is very short, ending before half the length of Rs, while in R. ( R.) setosa sp. nov. this vein ending just beyond half the length of Rs, measured from the fork of Rb. In contrast to R. ( R.) setix Podenas, 2006 comb. nov. in R. ( R.) setosa sp. nov. crossvein m-cu is situated beyond half the length of the d-cell, measured from the fork of Mb, R 3 is shorter than the distance between the tips of R 1 and R 3, almost straight vein R 4 is 4 times as long as R 3. R. ( R.) setix Podenas, 2006 comb. nov. crossvein m-cu is situated beyond half the length of d-cell, R 3 is shorter than the distance between the tips of R 1 and R 3, almost straight vein R 4 is 4 times as long as R 3. In R. ( R.) setix Podenas, 2006 comb. nov. m-cu situated before d-cell, R 3 is longer than the distance between the tips of R 1 and R 3, R 4 is arched and is only 3 times longer than R 3. Moreover, in a species described from the Eocene of the Green River, USA Rhabdomastix scudderi vein Sc is very elongate, ending just before the bifurcation of Rs, tip of vein A 2 is just before the bifurcation of Rs, while in R. ( R.) setosa sp. nov. Sc ending just beyond half the length of Rs, and vein A 2 terminating before fork of Rb. Stratigraphic and geographic range.—Baltic amber is dated by some authors to middle Eocene age (Lutetian Stage; 47.8–41.3 Ma) ( Wolfe et al. 2016), but the age range of this fossil resin is still under debate, dated by Grimaldi and Ross (2017) as Priabonian, based on pollen, spores and phyto- plankton of the amber-bearing layer, the Blue Earth. The specimen was collected at the Baltic area, the Blue Earth (Blaue Erde) ( Wolfe et al. 2016).

Rhabdomastix ( Rhabdomastix) woottoni sp. nov. Figs. 5 View Fig , 6 View Fig .

ZooBank LSID: lsid:zoobank.org:act: 92A02AC5-1693-4BC0-AB01- CBE1560931CD

Etymology: Dedicated to the outstanding invertebrate researcher, Rob- in J. Wootton (Department of Biological Sciences, University of Ex- eter, UK).

Holotype: GMUG 80 View Materials , male, the specimen is poorly preserved, the head is not well visible, partially damaged. (coll. Manfred Kutscher).

Type locality: Bitterfeld, Upper Saxony ( Sachsen-Anhalt), Germany .

Type horizon: Cottbus Formation, “Glimmersand”, middle–upper Eocene.

Material.— Holotype only.

Diagnosis.—Antennae very elongate, thin, much longer than body, 1.5 times longer; almost black, small spots usually present at base and distal part of flagellomeres, longer than wing; flagellomeres very narrow, significantly elongate, length of flagellomeres 1–3 corresponding to approximately 5 times (first flagellomere) or 6 times (second and third flagellomere) width of each of them, with numerous short setae, flagellomeres 4–9 elongate, corresponding to approximately 26 times their width, flagellomeres 10–14 shorter than oth- ers, length of last segment corresponds to half of penultimate one and 3 times its width, the setae of flagellomeres 4–9 very few and short, much shorter than length of segment on which they occur; tip of Sc beyond half length of wing, beyond half of Rs; Rs shorter than R 2+3+4 and R 4 combined by about 0.2 times of its length; tip of R 1 opposite half of d-cell, opposite approximately half length of R 2+3+4; length of R 4 4 times length of R 3, R 4 only slightly shorter than R 2+3+4; distance between tip of R 1 and R 3 longer than R 3; M 3 1.5 times longer than d-cell; m-cu just behind half of d-cell; d-cell length corresponding to 1.5 times its width, only slightly narrowed at base, slightly widened in distal part; anal angle expanded; distance between the tips of A 1 and A 2 corresponds to almost 5 times distance between tips of Cu and A 1; tip of A 2 before Rb fork; tip of A 1 beyond Rs fork; outer gonostylus elongate, narrow, sharply tipped, with one thick setae in apical part, only slightly longer than inner gonostylus, pointed at the end, with two thick setae at the end; haltere less than 0.25 times of wing length.

Description.— Body: 2.54 mm long, dark brown, wing without color pattern, pterostigma absent, haltere significantly elongate.

Head: 0.35 mm wide ( Fig. 5A View Fig 4); antenna elongate ( Figs. 5A View Fig 1 View Fig , A 3 View Fig , 6A View Fig 1 –A View Fig 4), very thin, scape pear-shaped, elongate, longer than its width, significantly expanded distally; pedicel short and very wide, wider than its length, a few elongate setae in the distal part of the scape and pedicel; the last flagellomere bluntly ended with two setae on the tip; antenna 4.40 mm long: scape 0.12 mm long; pedicel 0.09 mm long; flagellomeres: 1/ 0.22 mm; 2/ 0.27 mm; 3/ 0.36 mm; 4/ 0.46 mm; 5/ 0.45 mm; 6/ 0.45 mm; 7/ 0.41 mm; 8/ 0.41 mm; 9/ 0.40 mm; 10/ 0.36 mm; 11/ 0.17 mm; 12/ 0.09 mm; 13/ 0.08 mm; 14/ 0.06 mm; palpus ( Fig. 6A 6 View Fig ) 0.55 mm long (1/ 0.09 mm; 2/ 0.11 mm; 3/ 0.13 mm; 4/ 0.22 mm); palpomeres narrow and elongate, first and second palpomere of comparable length, approximately 2 times as long as wide, slightly expanded distally, the third palpomere longer than the first and the second but shorter than the last one, third palpomere 4 times as long as wide, the last palpomere 6 times as long as wide; each palpomeres with a few setae, slightly longer than the width of segments bearing them and much shorter than the length of the segments on which they occur.

Thorax: Wing 4.45 mm long, 1.52 mm wide, almost 3 times as long as wide ( Figs. 5A View Fig 2 View Fig , 6A View Fig 5 View Fig ); crossvein (h) positioned at the distance of 0.1 times of the length of the wing, measured from its base; crossvein sc-r occurs at the distance from the tip of the vein Sc corresponding to 3 times of its length; the distance between the tips of Sc and R 1 slightly longer than the distance between the tips of R 1 and R 3; R 3 short, shorter than half the distance between the tips of R 1 and R 3; M 1+2 more than 2 times as long as the d-cell; M 4 short, as long as d-cell; Mb 3 times as long as M 3; the section of the Cu from the point of connection of the Cu with crossvein m-cu to the edge of the wing almost straight; the distance between the tips of M 1+2 and M 3 shorter than the distance between the tips of M 3 and M 4; distances between the tips of M 3 and M 4 and the tips of M 4 and Cu comparable; the distance between the tips of M 4 and Cu 0.3 times longer than the distance between the tips of Cu and A 1; the distance between the tips of A 1 and A 2 2 times longer than the distance between the tips of M 4 and A 1; A 1 slightly curved, A 2 sinusoidal.

Haltere: 0.57 mm long, stem massive, only slightly longer than knob.

Hypopygium: 0.84 mm long, gonocoxites massive, elongate 2 times as long as wide with numerous long and thick setae ( Figs. 5A 5 View Fig , 6A View Fig 7 View Fig , A 8 View Fig ).

Remarks.—The features which allow to include the species within the subgenus Rhabdomastix are: elongate antennae, much longer than body length, crossvein well developed, d-cell hexagonal, distal part of M 1+2 and M 3 arched, outer gonostylus longer than inner gonostylus.

Rhabdomastix ( R.) woottoni sp. nov. differs from the other species belonging to the subgenus Rhabdomastix represented in Cenozoic fossil resins by the proportions of the length of the antennae in relation to the length of the body. The antennae of this species are much longer than the body, about half its length, very elongate and thin. The individual flagellomeres are very elongate and narrow, the scape and pedicel are wide, massive, much wider than the other flagellomeres. In addition, there are single, clear, almost black color spots on the antenna and relatively short, sparse setae. So far, no fossil species of the Rhabdoamastix genus have had this type of antennae. In other species belonging to the subgenus Rhabdomastix , represented in Cenozoic fossil resins, no color spots are observed on flagellomeres, the setae of this part of the body are more pronounced, usually numerous and more elongate. The shape of the scape and pedicel are also slightly different in the remaining species within the subgenus Rhabdomastix represented in Cenozoic fossil resins, they are not so massive in relation to the flagellomeres, unlike in R. ( R.) woottoni sp. nov. Moreover, R. ( R.) woottoni sp. nov. differs from the species described from Eocene sediments from Green River, USA R. scudderi in the wing venation. Vein Sc in R. scudderi is very elongate, ending just before the Rs fork, and the vein A 2 achieves the edge of the wing just before the Rs fork, while in R. ( R.) woottoni sp. nov. it is much shorter, ended in half the length of Rs, and the end of the A 2 vein is situated far before the fork of Rb, measured from the base of the wing.

Stratigraphic and geographic range.—Bitterfeld amber is believed to be approximately the same age as Baltic amber Szwedo and Sontag 2013), but it came probably from distinct ecosystems. Biterfeld amber belongs to the same group of ambers as Baltic amber, with an age similar to that of Baltic amber, as indicated by the dipteran species similarity preserved in these fossil resins. The similarity of the species preserved as an inclusions in this fossil resin contradicts the large age difference of these fossil resins. The differences found seem to reflect differences ecological conditions, not age (Standtke 2008). Some recent geochronological efforts Knuth et al. 2002; Blumenstengel 2004) date deposits of Bitterfeld amber as the late Oligocene (Chattian; 23.0– 28.1 Ma), some authors date the deposits of this fossil resin as Early Miocene (e.g., Barthel and Hetzer 1982; Rikkinen and Poinar 2000). But, some have argued that Bitterfeld amber being merely a younger redeposited fraction of primary Eocene Baltic amber ( Szwedo and Sontag 2013; Wolfe et al. 2016), the resin can be dated on middle–late Eocene Drohojowska et al. 2024). The specimen was collected at the Cottbus Formation near the town of Bitterfeld in Upper Saxony ( Sachsen-Anhalt) ( Wolfe et al. 2016).

Some species were previously described by Podenas 2006) and have not been classified into any of the subgenera. Features such as the complete atrophy of r-r (R 2), presence of sc-r, the bifurcation of Rb before half the length of the wing, the presence of small, hexagonal d-cell shorter than the length of the vein M 3, a cleary arched distal part of part M 1+2 and M 3, and the inner gonostylus shorter than the outher gonostylus, allow the following three species: Rhabdomastix ( R.) grussica Podenas, 2006 comb. nov., Rhabdomastix ( R.) setix Podenas, 2006 comb. nov., Rhabdomastix ( R.) mastix Podenas, 2006 comb. nov, all from the Baltic amber, to be included into the subgenus Rhabdomastix .

Rhabdomastix ( Rhabdomastix) grussica Podenas, 2006 comb. nov.

2006 Rhabdomastix View in CoL (?) grussica ; Podenas 2006: 46.

Remarks.—The species is characterized by elongate antennae, elongate flagellomeres with numerous setae and a very small apical segment, antennae longer than the body and wings. The wings of this species are typical for the genus. Hypopygium is characterized by straight elongated gonocoxites and long, slender outer gonostylus, many setae occur on inner gonostylus, interbase are long, with a straight ae- deaus ending before tip of interbase and by slightly extended at mid-posterior margin ninth sternite (after Podenas 2006).

Rhabdomastix ( Rhabdomastix) setix Podenas, 2006 comb. nov.

2006 Rhabdomastix View in CoL (?) setix ; Podenas 2006: 50.

Remarks.—The species is characterized by long antennae, longer than the body, with many long setae and a small apical segment, much smaller than the previous one. The wings are typical for the genus. Hypopygium of this species is characterized by long, slender bare outer gonostylus, without apical spine, fleshy inner gonostylus with straight posterior margin and slightly curved apex (after Podenas 2006).

Rhabdomastix ( Rhabdomastix) mastix Podenas, 2006 comb. nov.

Figs. 7 View Fig , 8 View Fig .

2006 Rhabdomastix View in CoL (?) mastix sp. nov.; Podenas 2006: 47, figs. 27–30.

Material.— ISEA PAS MP /3321, female from Baltic amber, Lutetian, middle Eocene, 47.9–41.3 Ma.

Emended diagnosis.—Antennae longer than body, shorter than wings, without color pattern; flagellomers 1–13 narrow of length corresponding to approximately 7 times their width, last flagelomere approximately 0.3 times shorter than penultimate one; setae shorter than flagellomeres bearing them, densely spaced; Sc terminating before half length of wing, opposite 0.3 times of Rs; Rs shother than R 2+3+4 and R 4 combined, approximately 0.2 times of its length; R 1 terminating opposite end of d-cell, opposite of 0.8 times of R 3+4; length of R 4 corresponds to 4 times length of R 3; R 4 longer than R 2+3+4 by about 0.2 times of its length; distance between tips of R 1 and R 3 longer than R 3; M 3 1.5 times longer than d-cell; m-cu situated in the middle of length of d-cell, d-cell length corresponding to 2 times its width, narrow at base, extended in the distal part; anal angle unexpanded; distance beetween tips of A 1 and A 2 correspond to almost 2.5 times distance between tips of Cu and A 1; tip of A 2 before Rb fork; A 1 before Rs fork; posterior edge of outer gonostylus serrated; haltere elongate, as long as 0.2 times wing length.

Description.— Body: 3.39 mm long, brown ( Fig. 7A View Fig 1 View Fig ), wing without color pattern, pterostigma absent, haltere significantly elongate ( Fig. 7A View Fig 2 View Fig ).

Head: 0.30 mm wide ( Fig. 7A View Fig 1 View Fig ); antenna with cylindri- cal scape, narrowed at the base, slightly wider in the distal part ( Figs. 7A View Fig 1 View Fig , 8A View Fig 2 View Fig ), scape and pedicel slightly longer than their width; pedicel with a few setae; flagellomeres 1–13 of comparable length; the last flagellomere with two setae at the tip, penultimate one 3 times longer than last one; setae on flagellomers 3–15 longer than the width of the flagellomeres bearing them, shorter than half the length of these segments; antenna 1.09 mm long: scape 0.06 mm; pedicel 0.09 mm; flagellomeres: 1, 0.07 mm; 2, 0.07 mm; 3, 0.07 mm; 4, 0.07 mm; 5, 0.07 mm; 6, 0.07 mm; 7, 0.07 mm; 8, 0.07 mm; 9, 0.07 mm; 10, 0.07 mm; 11, 0.07 mm; 12, 0.07 mm; 13, 0.07 mm; 14, 0.03 mm).

Palpus: 0.36 mm long (1, 0.06 mm; 2, 0.08 mm; 3, 0.08 mm; 4, 0.14 mm, Figs 7A View Fig 1 View Fig , 8A View Fig 3 View Fig ), palpomeres elongate, palpomeres 1–3 of comparable length, the last palpomere 2 times longer than penulitmate one; first palpomere 3 times as long as wide, second palpomere 2 times as long as wide, third palpomere 2.5 times as long as wide; the last palpomere elongate, 5 times as long as wide; each palpomere with a few elongate setae, longer than wide but shorter than palpomeres bearing them.

Thorax: Wing 3.91 mm long, 0.79 mm wide, 3.5 times as long as wide ( Figs. 7A View Fig 1 View Fig , 8A View Fig 1 View Fig ); the distance between tips of Sc and R 1 5 times longer tan the distance between the tips of R 1 and R 3; R 3 short, slightly shorter than the distance between the tips of R 1 and R 3; M 1+2 almost 2 times longer than length of d-cell; vein Mb approximately 2.5 times longer than the M 3; Cu from the point of connection with crossvein m-cu to the edge of wing slightly curved; the distance between the tips of M 1+2 and M 3 shorter than 0.25 times of its length, shorter than the distance between the tips of M 3 and M 4; the distance between the tips of M 3 and M 4 slightly longer than the distance between the tips of M 4 and Cu; the distance between the tips M 4 and Cu and the tips Cu and A 1 comparable length; the distance between the tips of A 1 and A 2 longer than 0.2 times the distance between the tips of M 4 and A 1; A 1 and A 2 almost straight.

Haltere: 0.60 mm long, sterm narrow, 2 times longer than knob ( Fig. 7A View Fig 2 View Fig ).

Ovipositor: 1.13 mm long, strongly sclerotized; cerci elongate, narrow and sharply ended; valves relatively short, narrow, 5 times as long as wide ( Figs. 7A View Fig 1 View Fig , A 3 View Fig , 8A View Fig 4).

Remarks.—Characters of wing morphology (female wing venation is almost identical compared to the male’s wing venation), as well as the ratio of the length of the hatltere to the length of the wings of the first pair allowed to classify female as Rhabdomastix ( R.) mastix Podenas, 2006 comb. nov. In the female, just like in the male, the halteres constitutes 0.25 times of the length of the wings and are very elongate.

In contrast to the other species within the subgenus Rhabdomastix represented in Cenozoic fossil resins in R. ( R.) mastix Podenas, 2006 comb. nov. the haltere is as much as 0.25 times of the length of the wing, in other species haltere is shorter than 0.25 times of the wing length.

Stratigraphic and geographic range.—Baltic amber is dated by some authors to middle Eocene age (Lutetian Stage; 47.8–41.3 Ma) ( Wolfe et al. 2016), but the age range of this fossil resin is still under discussion, dated by Grimaldi and Ross (2017) as Priabonian, based on pollen, spores and phy- toplankton of the amber-bearing layer, the so-called Blue Earth. The specimen was collected at the Baltic area, the Blue Earth (Blaue Erde) ( Wolfe et al. 2016).