Tethepomyia

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 : 60-62

Tethepomyia coxa, new species

Figures 21 , 53

DIAGNOSIS: Distinguished from other species in the genus by the greatest reduction in wing venation, no vestige of Rs or Cu remaining. Further distinguished from T. zigrasi (also in Burmese amber, known as female) by that species having very hunched scutum and retaining vestiges of Cu and A; from T. buruhandi (Spanish amber), which retains vestige of Cu; and from T. thauma (New Jersey amber), which retains vestige of Rs and the male genitalia are not dorsoflexed.

DESCRIPTION: Based on male. A minute fly, 1.52 mm body length; thorax length 0.43 mm; abdomen length 0.79 mm; wing length 1.12 mm. Head large, hemispherical (male), thorax compact, abdomen slender, wing short with highly reduced venation, body devoid of setae/setulae, with just sparse microtrichia in areas. Head: Oblong, with very large holoptic eyes. Eye in lateral view occupies all of lateral surface; also occupies most of dorsal, frontal, and much of ventral surfaces of heads. Eye bare, facets differentiated dorsoventrally: ventral facets ca. 0.7× diameter of dorsal ones; dividing line slightly below middle of eye. Ocelli on raised tubercle on vertex of head. Face, proboscis, mouthparts, antenna obscured by crystalline coating. Occiput concave. Thorax: Compact, short; flattened dorsally, depth shallow in lateral view; dorsal surfaces of scutum and scutellum in same plane. Antepronotum short. Scutum with faint paramedian sulci on anterior part of scutum. Postpronotal lobe flattened, slightly projecting, ledgelike. Notopleural suture wide, membrane very exposed; anepisternal-anepimeral cleft wide, membrane very exposed; anepimeron small, isolated by membrane (much of pleura obscured). Katepisternum small, shallow, ventral portion at same level as dorsal portion of mesocoxa. No proscutellum; scutellum short, broad; mediotergite (subscutellum?) bulging, very visible dorsally; metanotum articulating with metakatepisternum, latter pointed posteriorly. Wing: Highly reduced venation, short and broad, W/L 0.42. Vein C lost. Incomplete, faint vestiges of only R and M stems (no branches) remain, as nebulous infuscation with slightly denser microtrichia; M reaching to about middle of wing. Very faint pterostigma between middle of R and anterior edge of wing. Wing entirely with dense microtrichia, slightly finer and denser on pterostigma and veins. Anal lobe present. Legs: Relatively short. All coxae well separated, short; metacoxa distinctly separated from mesocoxa, articulating with metakatepisternum. No metacoxal tubercle. Trochanters well developed. Meso- and metafemora expanded apically, especially latter. All femora with long, wide, ventral “notch” (femoral-tibial articulation) on distal half. Tibiae expanded apically, especially metatibia, slightly curved (as if to fit against ventral surface of femur). No tibial spurs, bristles, or setae. Basitarsomere very short, length approximately equal to that of tarsomeres 2+3. Leg segment lengths: tibia> femur> tarsus. Pretarsus: claws well developed; pulvilli ca. 0.5× length of claws; empodium not observable (either minute or setiform). Abdomen: Slender, cylindrical, slightly longer than length of head + thorax. Tergites and sternites well developed; 8 tergites visible, t1 small, t2–7 large, t8 a small dorsal lobe. Male genitalia dorsoflexed, with large pair of dorsal lobes (“X” in fig. 21C, D) articulating basally within ventral sclerite (“Y” in fig. 21C, D); lobe pair (X) and ventral sclerite (Y) either cerci and sternite 9, respectively, or—if eremoneuran—surstyli and epandrium, respectively.

TYPE: Holotype, male, AMNH Bu-SE10.

ETYMOLOGY: Taken directly from coxa, and used as a noun in apposition, in reference to the unusual configuration of the metacoxa with the metanotum and metakatepisternum.

COMMENTS: The holoytpe is in a tiny, square chip of amber 5 × 5 × 1.5 mm piece of amber, trimmed from a large, deep-colored cabochen 21 × 30 × 16 mm, which also contains an empidoid fly and Coleoptera. Without new imaging of the other Tethepomyia species , it is uncertain whether the unusual thoracic morphology of T. coxa is unique to the genus or not. The metacoxa is shifted posterodorsad, such that it articulates with the metakatepisternum. This coxa is also elongate and has a deep dorsolateral excision. The holotype of T. coxa certainly has the best thoracic preservation among the five known specimens of the family. Unfortunately, portions of the head are obscured, so details of the antenna and mouthparts are not visible.

Figures

FIG. 21. Tethepomyia coxa (Tethepomyiidae), new species, holotype AMNH Bu-SE10. A. Wing. B. Head and thorax, left lateral view. C. Male terminalia, left lateral view. D. Male terminalia, posteroventral view. E. Metafemur, ventral view, showing long notch at the femoral-tibial joint. F. Metatibia and tarsi, lateral view. Abbreviations: anepm, anepimeron; cx, coxa; katpst, katepisternum; tr, trochanter. X, either cerci or surstyli; Y, either sternite 9 or epandrium (see text).

FIG. 53. Tethepomyia coxa, new species (Tethepomyiidae), holotype AMNH Bu-SE10. A. Habitus, left lateral. B. Detail of wing and abdomen, showing density of microtrichia on wing membrane.