Kumaromyia burmitica Grimaldi & Hauser

Grimaldi, David A., Arillo, Antonio, Cumming, Jeffrey M. & Hauser, Martin, 2011, Brachyceran Diptera (Insecta) in Cretaceous ambers, Part IV, Significant New Orthorrhaphous Taxa, ZooKeys 148, pp. 293-332 : 314-317

Kumaromyia burmitica Grimaldi & Hauser sp. n. Fig. 8

Diagnosis.

As for the genus.

Description.

Small fly, total body length ca. 2.70 mm, thorax length 1.0 mm, wing length (estimated) 2.50 mm. Head: Large, with large eyes. Eyes bare, hemispherical in lateral view (posterior margin flat), no dorsoventral differentiation of facets; inner margins of eyes parallel, separated by distance approximately equal to width between antennal bases. Frons slightly convex, not protruding anteriad; with numerous fine setulae, without calli. Face ("subcranial cavity") depressed, dark (sclerotized?), glabrous. Antennal scape and pedicel small, approximately equal in size, devoid of thick setae; basal flagellomere largest antennomere, drop-shaped, with dense setulae (no setae); apical two antennomeres (including apical style) small, fine, with style slightly longer than penultimate antennal article. Maxilla with bases (cardostipites) sclerotized and partially fused, palp1-segmented. Labellum slightly larger than palps. Postgena well developed, with numerous fine setae (pilosity). Thorax: Deep in lateral view, pleura apparently devoid of fine or bristle-like setae; scutum with at least 8 pairs of setae [dorsal view, including scutellum, obscured]. Scutum with 3 pairs of notopleurals and 5 pairs in supra-alar region and some setulae; no cervical/postcervical setae. Legs: With thick, stiff setae, primarily on tibiae; fore tibia slender, hind tibia thickest. Fore leg: femur with lateral row of ca. 10 fine setae, tibia with anterior row of 4-5 setae, 4 pre-apical setae. Mid leg: Femur apparently devoid of setae, tibia with 3 evenly-spaced setae on dorsal surface, 2 more ventrad, 4 apically. Hind leg: Coxa with small knob on ventral surface [best seen in left coxa]; femur devoid of setae, tibia with dorsal row of 3-4 setae, lateral row of 3 setae, ventral row of 3-4 setae. Basitarsomere on each leg equal in length to (or slightly longer than) combined length of distal tarsomeres. Each tarsomere with ca. 4 short, stiff setae on rim of distal end. Pretarsus with pair of large pulvilli, empodium setiform. Wing: Large, length nearly equal to that of body. Crossvein h long (space between Sc and C deep); Sc long, length approximately ½ that of wing and slightly shorter than length of R1; apex of Sc apparently incomplete (not meeting C). Apices of Sc and R1 without pterostigma surrounding apices. Fork of R and Rs deep, proximal to level of vein h. R2+3 straight, without apical curve. Fork of R4+5 not widely divergent; R5 in line with stem of R4+5, apex of R5 ending very near apex of wing (not posterior to it); R4 slightly curved, distinctly shorter than R5. Cell d slender, greatest width <0.25 × length. Veins M1 and M2 slightly divergent, M2 and M3 very divergent, all M veins attached to apex of cell d. Apex of M3 meeting apex of CuA1 at wing margin. ABDOMEN: Short, only slightly longer than thorax; details (e.g., sternites, genitalia) not observable.

Type.

Holotype, female, AMNH Bu131: Myanmar: Kachin State, near Mytikyina (mid-Cretaceous: Late Albian - Cenomanian). Specimen is complete, but the right wing (the only one observable) is folded, and most of the dorsal view is obscured, compromising a complete reconstruction of the venation (fig. 8). The fly is complete, though slightly compressed and with a slight coating of particulate matter over some areas. Its left side is lying on a rough surface of the amber, which obscures that view. The piece also contains some twisted strands of spider webbing.

Etymology.

In reference to the country of origin.

Discussion.

There is little question this fossil belongs to the therevid group, albeit unusually small (within the range in body size of some apsilocephalids and a few genera of Phycinae , such as Efflatouniella Kröber, 1927). Therevid-group features include the antennal structure, bristle-like setae on the scutum and on the legs, the small knob on the hind coxa, as well as the venation. Unlike most Therevidae , Kumaromyia lacks any pruinosity and pilosity (except for the postgena), although Xestomyzinae and Agaphotinae are also robust and have sparse pilosity. Kumaromyia lacks any thick setae that typically encircle the scape and/or pedicel subapically in Therevidae . Also, Kumaromyia has R4 and R5 above the wing tip, whereas in Therevidae these are above and below the wing tip, respectively. Unlike Apsilocephalidae , Kumaromyia has a one-segmented palp, vs. two-segmented in Apsilocephalidae , where the basal segment is distinctively thin and long (oddly, palp segmentation and structure was not described for Kaurimyia ). The antennal stylus and stout body in Kumaromyia is much more similar to that of Clesthentia , as the stylus in Apsilocephala , Kaurimyia , and even Burmapsilocephala is long and thin. It is quite possible that Kumaromyia is a stem-group taxon for the therevid-family group, not necessarily belonging within Apsilocephalidae or Therevidae .

Fossil Therevidae are scarce, with only five definitive species known, all from the Tertiary. Hauser (2007) and Hauser and Irwin (2005) revised the fossil species:

Ambradolon grimaldii Metz and Irwin 2000: Early Miocene Dominican Republic amber

Arctogephyra agilis (Meunier 1908): mid-Eocene Baltic amber

Dasystethos hoffeinsi Hauser 2007: mid-Eocene Baltic amber

Kroeberiella pinguis (Loew 1850): mid-Eocene Baltic amber

Palaeopherocera scudderi (Cockerell 1909): uppermost Eocene, Florissant, Colorado, USA

Fossil Apsilocephalidae range from the Cretaceous to early Tertiary:

Apsilocephala pusilla (Hennig 1967): mid-Eocene Baltic amber

Apsilocephala vagabunda (Cockerell 1927): uppermost Eocene, Florissant, Colorado, USA

Burmapsilocephala cockerelli Gaimari and Mostovski 2000: mid-Cretaceous Burmese amber

Undescribed sp.: Early Cretaceous amber, Wealden, UK ( Chandler 2010: plate 32, fig. 2).

The position of Psilocephala electrella Cockerell 1920 within the therevoid group is uncertain.