Tabanipriscus transitivus, Grimaldi, 2016

Grimaldi, David A., 2016, Diverse Orthorrhaphan Flies (Insecta: Diptera: Brachycera) In Amber From The Cretaceous Of Myanmar: Brachycera In Cretaceous Amber, Part Vii David A. Grimaldi, Bulletin of the American Museum of Natural History 2016 (408), pp. 1-132 : 43-45

Tabanipriscus transitivus , new species

Figures 14 , 47

DIAGNOSIS: As for genus, by monotypy.

DESCRIPTION: Based on unique female. Body length ca. 8.92 mm; antennal length 4.15 mm; wing length 6.45 mm; abdomen length 4.15 mm. Head: Very rounded, occiput flattened (slightly

concave); eyes large, dichoptic, completely bare, no differentiation of facets, eyes occupy entire lateral surface of head and much of frontal surface. Frons bare, without callosities; very narrow, width ca. equal to 6× diameter of eye facet, margins virtually parallel. Ocelli large, on shallow mound. Antenna: Sockets extensively membranous. Scape somewhat cylindrical, ventral surface proximally extended, distally with stiff, short setae; pedicel goblet shaped, with apical ring of short, stiff setae. Flagellum with at least 7 (probably 8) articulating flagellomeres; basal flagellomere broader than all other antennomeres; flagellomeres gradually decrease in width apicad, apical one 0.25× width of basal one. Minute terminal stylus appears to be present. Clypeus not particularly bulging, except for pair of rugose lobes/callosities below antennal bases, and small lobe at base of clypeus. Lateral margins of clypeus forming ridge just medial to deep parafacial sulci. Cheek near base of mouthparts with membranous areas. Occiput and postgena with fine erect setae. Mouthparts: Palp 2-segmented; basal segment more slender and cylindrical, with dense, stiff, fine setae; apical palp larger, slightly arched (dorsally convex), with dense microtrichia and some thick setulae (apical portions lost); palps held above proboscis, convergent apicad. Apex of proboscis lost, but clearly short; labium short, with long, fine, stiff setae; labellum large, fleshy; laciniae and mandibles partially exposed. Thorax: Dorsally light, ochre; devoid of macrosetae, with vestiture of fine, short setulae; fine macrosetae on prepisternum, preepimeron, and anepimeron; prescutellum present; scutellum (deformed in unique specimen), dark (blackish brown), with short pilosity (subscutellar area obscured). Metaspiracular and suprametacoxal areas obscured. Wing: Largely hyaline, except for pterostigmatic area around apex of R 1; minute microtrichia over entire wing membrane. Wing broad in middle (W/L = 0.41), significantly tapered apicad, anterior edge not straight, slightly convex. Basicosta deeply incised, slender, lappetlike; C circumambient, base very thick, with fine, stiff setae; tips of wings lost. Crossvein h very faint; Sc straight, upturned only at tip, length 0.5× wing length; R 1 very close to Sc, length 0.65×; stem of R and base of R 1 with 2–3 rows microtrichia on dorsal surface, diminished to 1 row apicad; apex of R 1 significantly thickened. Fork of R 4+5 long, base diverging near level of cell d apex (vs. significantly distad); R 4 and R 5 mod- erately divergent, tips of both probably straddling wing apex (based on course of R 4); preserved portion of R 4 only very slightly sinuous. Cell bm slightly longer and broader than cell br; cell d straight (not arched), narrow (W/L 0.22); vein M 1 slightly longer than cell d, veins M 2, M 3 shorter; M veins very slightly divergent; M 3 and CuA 1 slightly convergent; stem of CuA with row of microtrichia on dorsal surface. Cell cup present, tips of CuA 2 and A 1 meeting just before wing margin; vein A 2 present, short. Anal lobe well developed, alula present but shallow, basalmost area of wing obscured (e.g., presence/ absence of calypters). Legs: Dark brown, with dense vestiture of short, stiff setulae (especially on tibiae and tarsi); coxae with long, fine pilosity, metacoxa without peg on anterior surface; tibial spurs 0-2-2, middle spurs longest; empodium pulvilliform. Abdomen: Broad, dorsoventrally flattened; lateral margins of tergites and sternites meeting laterally; (middle portion of tergite 1 obscured); tergites and sternites with dense, short pilosity. Cerci 2-segmented, basal segment symmetrical, ca. twice the size of apical segment. Tergite 9 not visible.

TYPE (S): Holotype, female, AMNH Bu-SE2/10.

ETYMOLOGY: From the Latin transitivus (“transitional”), in reference to the phylogenetically intermediate morphology of this tabanomorphan.

COMMENTS: The holotype is in a dark ambercolored piece 15 × 17 × 6 mm, which also contains fragments of small arthropods, frass pellets, a small fragment of bark, and twisted spider webbing. The fly is moderately well preserved, missing only portion of the right eye (an optic lobe is visible), tips of the palps, proboscis, and wings, and distal segments of the hind legs. The thorax and abdomen are somewhat crumpled and deformed, obscuring some critical features such as the metaspiracular, suprametacoxal, and subscutellar areas, as well as tergite one.

Genus Cratotabanus Martins-Neto and Kucera-Santos

Cratotabanus Martins-Neto and Kucera-Santos, 1994: 291 .

Cratotabanus: Grimaldi et al., 2011 (revised diagnosis).

EMENDED DIAGNOSIS: Modified and updated from Grimaldi et al. (2011) based on new material in Burmese amber: M 1 (and sometimes M 2 and

M 3) long, length(s) about equal to that of cell d (vs. significantly shorter in modern genera); R 5 only slightly deviated from path of stem vein R 4+5. Further, in C. asiaticus , n. sp., postmetaspiracular scale lacking; female cercus 2-segmented; tergite 1 divided, tergite 10 undivided. Differs from Laiyangitabanus (monotypic: formosus ) based on venational characters: in Cratotabanus wing apex more acute; R 2+3 straight (vs. slightly sinuous), R 4 -R 5 fork larger, more asymmetrical (i.e., R 4 significantly longer, quite sinuous), cell d slightly narrower, r-m very close to base of cell d (vs. at approximately basal third of cell) (fig. 16).

TYPE SPECIES: Cratotabanus stenomyomorphus Martins-Neto and Kucera-Santos , in limestone from the Crato Formation (Aptian) of Brazil.

COMMENTS: There is no question about the tabanid identity of Cratotabanus , based on the observation of new details in this amber specimen. Cratotabanus newjerseyensis , also in Cretaceous amber (Turonian: New Jersey), was largely obscured. Although Cratotabanus asiaticus plesiomorphically lacks a developed postmetaspiracular scale, has a 2-segmented cercus, and tergite 10 is undivided, this species possesses the typical tabanid wing venation and head shape, and it has a large basal calypter and divided first tergite. These features cast significant light on the sequence of character evolution in tabanoids. Paleogeographic records of Cratotabanus are very similar to that of the Cretaceous family Zhangsolvidae (Stratiomyomorpha) (above; Arillo et al., 2015): both taxa are known from the Crato Formation of Brazil and in Burmese amber, and in adjacent areas of Laurasia ( Cratotabanus in New Jersey amber and Zhangsolvidae in Spanish amber); Zhangsolvidae is further known from the Cretaceous of China.

Figures

FIG. 14. Tabanipriscus transitivus (stem-group Tabanidae), new genus and species, holotype AMNH Bu SE2/10. A. Wing. B. Base of costal region of left wing, dorsal view. C. Female terminalia, oblique left lateral view. D. Head, right frontolateral view, as preserved. Panels C, D to same scale.

FIG. 47. Tabanipriscus transitivus, new genus and species (stem-group Tabanidae), holotype female, AMNH Bu-SE2/10. A. Habitus, ventrolateral view. B. Head, right lateral view. C. Habitus, dorsolateral view.