Dixella eomarginata Greenwalt and Moulton

Greenwalt, D, 2016, The first fossil New World Dixidae with a critical discussion of generic definitions, Palaeontologia Electronica 19 (3), pp. 1-32 : 7-8

publication ID

https://doi.org/ 10.26879/656

publication LSID

lsid:zoobank.org:pub:3FEDC26A-677F-451E-AC95-341AC229C7C8

persistent identifier

https://treatment.plazi.org/id/0EC67728-2799-4615-B318-3723C944DE99

taxon LSID

lsid:zoobank.org:act:0EC67728-2799-4615-B318-3723C944DE99

treatment provided by

Felipe

scientific name

Dixella eomarginata Greenwalt and Moulton
status

sp. nov.

Dixella eomarginata Greenwalt and Moulton , new species

Figures 3.2 View FIGURE 3 , 6 View FIGURE 6 , 7 View FIGURE 7

zoobank.org/ 0EC67728-2799-4615-B318-3723C944DE99

Etymology. The specific epithet is a combination of the Greek term eos, meaning dawn, and the specific epithet marginata , indicating similarity of the shape of the posterior margin of the wing with that of the extant Dixella marginata Loew, 1863 .

Holotype. Dixella eomarginata Greenwalt and Moulton , female; NMNH, USNM 553521 About USNM .

Type Horizon. Middle Eocene Coal Creek member, Kishenehn Formation.

Type Locality. Dakin site, Middle Fork of the Flathead River (Pinnacle, Montana) .

Differential Diagnosis. Distinguished from all other fossil Dixidae based on the presence of the following character states: wing emarginate between CuA1 and CuA2, wing length to body length ratio equal to 0.91, R 1 closer to C than R 2.

Description. Adult female ( Figure 6 View FIGURE 6 ), body length 3.8 mm.

Head. Black. Eyes dichoptic, spherical, diameter 0.26 mm, 0.12 mm. Maxillary palps not visible. Antennae not preserved intact, contiguous flagellomeres present, brown, filiform. Pedicel light brown, longer than wide. One maxillary palp present, poorly preserved, length 0.5 mm; length terminal segment 0.179 mm.

Thorax. Lateral view. Length 1.03 mm, black; lateral vittae absent; scutellum brown. Thoracic setae not visible.

Wings. Length 3.46 mm (measured from base of humeral crossvein), width 1.18 mm ( Figures 3.2 View FIGURE 3 , 7.1 View FIGURE 7 ). L/W ratio = 2.93. Vein R 2+3 arched. Vein Sc apex basal to origin of Rs (1.4 times distance between C, R1). Crossvein r-m basal to Rs bifurcation. Crossvein m-cu very lightly sclerotized, apex just distal to r-m terminus. A1 apex poorly preserved, basal to Cu bifurcation, distal to Sc apex. R 2+3 bifurcation significantly basal to M bifurcation. Ratios R 2 /M 2, M 2 /M 1, M 2 /M 1+2, R 2+3 /R 3 = 2.37, 0.71, 0.55, 0.44, respectively. Wing veins, margin with thin setae, length ≤ 20 μm. Wing posterior margin emarginate between CuA1, CuA2. Prominent false vein (?) between M, Cu continues between M 1+2,

GREENWALT & MOULTON: NEW WORLD FOSSIL DIXIDAE

CuA 1 (not present in the right wing). Haltere brown, length 0.53 mm long, knob oval, width 144 μm, length wide 207 μm.

Legs. All legs setose; metatibia expanded distally. Foreleg femur, tibia, tarsus lengths 1.28, 1.29, 1.65 mm, respectively. Midleg femur, tibia, tarsus lengths 1.71, 1.40, 1.78 mm, respectively. Hind leg femur, tibia, tarsus lengths 1.65, 1.56, 2.22 mm, respectively. Metapretarsal claws not preserved sufficiently to determine presence, absence of teeth.

Abdomen and genitalia. Abdomen light brown, length 2.66 mm (not including cerci). Segment 7 with single sclerotized spermatheca, oval, 154 μm x 115 μm. Tergite 9, posterior edge sternite 8 dark brown/black, more heavily setose than anterior portions of abdomen. Cerci dorsally situated, brown, setose, length 0.12 mm ( Figure 7.2 View FIGURE 7 ). Posterior margin sternite 8 lined by numerous setae approximately 35 μm long, Cerci, tergite 9 with several setae 70 μm or longer. Sternite 9 bulbous, protruding just below cerci.

Male unknown.

NMNH

Smithsonian Institution, National Museum of Natural History

Kingdom

Animalia

Phylum

Arthropoda

Class

Insecta

Order

Diptera

Family

Dixidae

Genus

Dixella

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