taxonID	type	description	language	source
0393156CFFEC9B50FCCEFC1922C0FBA9.taxon	type_taxon	Type species. Dixella lirio Dyar and Shannon, 1924	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFEC9B55FCC0FBAF20EDFC5E.taxon	description	Figures 1, 2, 3.1, 4.1, 5 zoobank. org / B 50 B 1127 - CA 1 E- 4395 - 9 A 74 - 60 B 1 AD 5701 CE	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFEC9B55FCC0FBAF20EDFC5E.taxon	etymology	Etymology. The specific epithet is Latin for “ untouched ”, an indication of the intact nature of this fossil.	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFEC9B55FCC0FBAF20EDFC5E.taxon	materials_examined	Holotype. Dixella intacta Greenwalt and Moulton, female; NMNH, USNM 546204. Type Horizon. Middle Eocene Coal Creek member, Kishenehn Formation. Type Locality. Deep Ford site, Middle Fork of the Flathead River (Pinnacle, Montana).	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFEC9B55FCC0FBAF20EDFC5E.taxon	diagnosis	Differential Diagnosis. Distinguished from all other fossil Dixidae based on the presence of one or more of the following character states: distinct stylized spade-shaped cercus (similar to Dixa brevis Garrett, 1924), first flagellomere very slightly fusiform, antenna length much more than combined lengths of head and thorax, wing length / body length ratio equal to one, and apex of R 1 closer to C than to R 2.	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFEC9B55FCC0FBAF20EDFC5E.taxon	description	Description. Adult female (Figure 1), body length 4.5 mm. Head. Black. Eyes dichoptic, large, oval with dorsal-ventral height (0.45 mm) greater than width (0.40 mm). Eyes separated by 0.12 mm. Maxillary palpus not visible. Antenna brown, 2.4 mm in length (Figure 2.1). Scape barely visible, small, approximately 40 μm in width. Pedicel subspherical, 104 μm wide, 118 μm long. Antenna with 14 flagellomeres, each setose. F 1 very slightly fusiform, 40 μm wide; F 2 – F 4 widths gradually decrease to 30 μm. F 5 (22 μm) more slender than F 4. F 5, subsequent flagellomere widths gradually decrease to 7 μm at F 14. Flagellomere lengths / widths (in mm) as follows: F 1 (0.30 / 0.04), F 2 (0.12 / 0.04), F 3 (0.16 / 0.03), F 4 (0.17 / 0.03), F 5 (0.23 / 0.02), F 6 (0.20 / 0.02), F 7 (0.19 / 0.02), F 8 (0.190.01), F 9 (0.18 / 0.01), F 10 (0.15 / 0.01), F 11 (0.13 / 0.01), F 12 (0.12 / 0.01), F 13 (0.12 / 0.01), F 14 (0.13 / 0.01). Thorax. Length 1.3 mm. Dark brown medial, lateral vittae covering most of scutum except for posteromedial portion and four medial light brown spots connecting medial, lateral vittae (Figure 2.2). Scutellum yellow. Acrostichal setae at lateral margin of medial vitta. Setae present along posterior margin of scutellum, lateral surface of mediotergite. Wings. Length 4.28 mm, width 1.37 mm (Figure 3.1). L / W ratio = 3.12. Vein R 2 + 3 arched. Sc apex even with Rs origin. Crossvein r-m single veinwidth distal to Rs bifurcation, slightly sigmoidal. Crossvein m-cu even with posterior point of r-m. A 1 apex slightly basal to Cu bifurcation, distal to Sc apex and Rs origin. R 2 + 3 bifurcation basal to M bifurcation. Length ratios R 2 / M 2, M 2 / M 1, M 2 / M 1 + 2, R 2 + 3 / R 3 = 2.6, 0.61, 0.54, 0.49, respectively. Vein CuP present. Wing surface covered with microtrichae; veins, margin of wing with spiniform setae 55 ± 15 μm in length. Haltere dark brown, length 0.59 mm with setae on anterior margin of proximal end, knob; knob spherical, diameter 155 μm; base black. Legs. All legs setose; hind tibia expanded distally. Foreleg femur, tibia, 5 tarsomeres lengths 1.38, 1.32, 0.9, 0.36, 0.23, 0.12, 0.14 mm, respectively. Midleg femur, tibia, 5 tarsomeres lengths 1.74, 1.58, 0.76, 0.42, 0.27, 0.14, 0.15 mm, respectively. Hind leg femur, tibia, 5 tarsal segments lengths 1.8, 1.83, 1.52, 0.53, 0.34, 0.18, 0.13 mm, respectively. Claws without teeth (Figure 4.1). Abdomen and genitalia. Abdomen brown, setose, length 2.84 mm (not including cercus); sternite 8, tergite 9 dark brown / black, more heavily setose than anterior portion of abdomen. With single sclerotized spermatheca, spherical, 0.17 mm in diameter. Cercus black, setose, shaped like stylized spade, length 0.12 mm (Figure 5). Male unknown.	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE99B54FF7DFBBC20EDF98E.taxon	description	Figures 3.2, 6, 7 zoobank. org / 0 EC 67728 - 2799 - 4615 - B 318 - 3723 C 944 DE 99	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE99B54FF7DFBBC20EDF98E.taxon	etymology	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.	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE99B54FF7DFBBC20EDF98E.taxon	materials_examined	Holotype. Dixella eomarginata Greenwalt and Moulton, female; NMNH, USNM 553521. Type Horizon. Middle Eocene Coal Creek member, Kishenehn Formation. Type Locality. Dakin site, Middle Fork of the Flathead River (Pinnacle, Montana).	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE99B54FF7DFBBC20EDF98E.taxon	diagnosis	Differential Diagnosis. Distinguished from all other fossil Dixidae based on the presence of the following character states: wing emarginate between CuA 1 and CuA 2, wing length to body length ratio equal to 0.91, R 1 closer to C than R 2.	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE99B54FF7DFBBC20EDF98E.taxon	description	Description. Adult female (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, 7.1). L / W ratio = 2.93. Vein R 2 + 3 arched. Vein Sc apex basal to origin of Rs (1.4 times distance between C, R 1). Crossvein r-m basal to Rs bifurcation. Crossvein m-cu very lightly sclerotized, apex just distal to r-m terminus. A 1 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 CuA 1, CuA 2. 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). 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.	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE89B5AFF68F98C23B3FFDF.taxon	description	Figures 3.3. 4.2, 8, 9 zoobank. org / 716 DBCD 1 - 3920 - 42 D 3 - 949 D-BEC 02984 A 27 F	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE89B5AFF68F98C23B3FFDF.taxon	etymology	Etymology. The specific epithet is derived from a combination of the terms curvi (L) meaning curved and stylus (L) meaning stalk or pike, and denotes the sharply curved gonostylus of this species.	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE89B5AFF68F98C23B3FFDF.taxon	materials_examined	Holotype. Dixella curvistyla Greenwalt and Moulton, male; NMNH, USNM 546860. Type Horizon. Middle Eocene Coal Creek member, Kishenehn Formation. Type Locality. Disbrow Creek site, Middle Fork of the Flathead River (Pinnacle, Montana).	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE89B5AFF68F98C23B3FFDF.taxon	diagnosis	Differential Diagnosis. Distinguished from the three previously described Eocene fossil Dixella based on wing width (1.32 mm vs. 0.56 in D. distans Hennig, 1966), length of flagellomere F 1 (0.234 mm vs. 0.415 mm in D. succinea Meunier, 1906) and form of the gonostylus (very long and narrow in D. filiforceps Hennig, 1966).	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE89B5AFF68F98C23B3FFDF.taxon	description	Description. Adult male (Figure 8), body length 3.36 mm. Head. Black. Eyes dichoptic, large, oblong, width 0.186 mm, length 0.284 mm. Three prominent setae at lateral margin of eye. Maxillary palp length 0.34 mm, two basal segments wider than long (31 x 41 μm); segments three and four 42 and 54 μm long, respectively, both 35 μm wide; terminal segment length 0.169 mm, width 21 μm, terminus with several short setae (Figure 9.1). Most distal flagellomeres missing (Figure 9.1). Scape black, large, subspherical, 72 μm in diameter. Pedicel black, globular, diameter 0.1 mm. Flagellomeres setose, light brown. F 1 cylindrical, diameter 32 μm, length 0.23 mm. F 2 – F 4 gradually decreasing in diameter. Thorax. Lateral view. Black, length 1.08 mm, no setae apparent. Wings. Length 2.89 mm (measured from base of the humeral crossvein), 1.17 mm wide. L / W ratio = 2.47. Vein R 2 + 3 arched (Figure 3.3). Vein Sc apex even with Rs origin. Crossvein r-m distal to Rs bifurcation. Crossvein m-cu even with r-m apex, less heavily pigmented than r-m. A 1 apex slightly basal to Cu bifurcation, distal to Sc apex, Rs origin. R 2 + 3 bifurcation even with M bifurcation. Ratios R 2 / M 2, M 2 / M 1, M 2 / M 1 + 2, R 2 + 3 / R 3 = 2.03, 0.70, 0.75, 0.52, respectively. Wing surface infuscate; veins, except M, Cu, margin of wing covered with setae. Haltere dark brown, length 0.48 mm; knob oblong, diameter 119 μm. Legs. All legs setose, brown. At least two legs, including left hind leg, with tarsal claws with four observable teeth (Figure 4.2). All legs mostly disarticulated; mid and hind tarsi identification based on swollen apical portion of metatibia, combined fragment lengths. The foreleg femur, tibia lengths 1.08 and 1.0 mm, respectively. Midleg femur, tibia, tarsus lengths 1.50, 1.13 mm, 1.70 mm, respectively. Hind leg femur, tibia, and tarsus lengths 1.30, 1.26, 1.9 mm, respectively. Abdomen and genitalia. Abdomen brown, setose, length 2.35 mm (including genitalia). Anterior half of abdomen with light bands of varying widths wherein setae are absent or reduced. Sternite 9 posterior margin with numerous setae. Gonocoxite length 220 μm, apical lobe length 79 μm, width 24 μm (Figure 9.2), distal margin with several prominent setae, each about 10 μm in length. Gonostylus length 158 μm, very broad, base 79 μm, midpoint 54 μm, bent approximately 75 degrees at midpoint, tapering to very fine point. Female unknown. GREENWALT & MOULTON: NEW WORLD FOSSIL DIXIDAE	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE69B43FF60FABD25F6FE7A.taxon	description	Figures 4.3, 10, 11 zoobank. org / E 669 A 17 A- 4957 - 483 C-ACC 4 - 5 E 8 BDF 6 CDF 7 A	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE69B43FF60FABD25F6FE7A.taxon	etymology	Etymology. The specific epithet is derived from a combination of the terms spinosa (L) meaning spiny and lobata (L) meaning lobed and refers to the spiniform shape of both the apical lobe and the tip of the basal lobe of the gonocoxite.	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE69B43FF60FABD25F6FE7A.taxon	materials_examined	Holotype. Dixella spinilobata Greenwalt and Moulton, male; NMNH, USNM 553522. Type Horizon. Middle Eocene Coal Creek member, Kishenehn Formation. Type Locality. Dakin site, Middle Fork of the Flathead River (Pinnacle, Montana).	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE69B43FF60FABD25F6FE7A.taxon	diagnosis	Differential Diagnosis. Distinguished from all other known fossil Dixidae based on one or more of the following characters: first flagellomere filliform, wing length to body length ratio equal to 0.95, R 1 much closer to C than R 2, antennal length (0.61 of its total body length), size of the gonocoxite and shape of the gonostylus.	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE69B43FF60FABD25F6FE7A.taxon	description	Description. Adult male (Figure 10), body length 3.5 mm. Head. Black; eyes dichoptic, large, spherical, diameter 0.222 mm. Maxillary palps long, length 0.34 mm, basal most segments not visible; segments four and five 88 x 40 and 230 x 27 μm (length x width), respectively. Antenna brown, relatively long (2.12 mm; Figure 10), thin. Scape and pedicel poorly resolved, pedicel spherical, 73 μm in diameter. Both F 1 apparently filiform although partially covered by foreleg; dimensions unknown. Widths F 2 – F 14 gradually decreasing. All flagellomeres setose. Thorax. Length 0.95 mm, black with dark brown medial, lateral vittae covering scutellum; scutellum light brown. Setae absent. Wings. Length 3.32 mm, width 1.08 mm. L / W ratio = 3.07. R 1 very close to costal vein; vein R 2 + 3 arched. Vein Sc apex basal to Rs origin (by distance 1.5 x distance separating C, R 1). Ratio R 2 + 3 / R 3 0.59. Wing surface covered with microtrichae; veins, margin covered with long setae approximately 59 μm in length. Haltere dark brown, length 0.55 mm, knob elongate 114 μm x 256 μm. Legs. All legs setose; hind tibia expanded distally. Foreleg femur, tibia, tarsus lengths 1.26, 1.07, 1.69 mm, respectively. Midleg femur, tibia, tarsus lengths 1.66, 1.42, 1.78 mm, respectively. Hind leg femur, tibia, tarsus lengths 1.56, 1.58, 2.0 mm, respectively; hind leg claws without apparent teeth (Figure 4.3). Abdomen and genitalia. Abdomen brown, setose, length 2.84 mm (including terminalia). Sternite 8, tergite 9 dark brown / black, more heavily setose. Terminalia width (at widest point of two gonocoxites) 0.419 mm, each gonocoxite approximately 0.202 mm long and 0.139 mm wide; gonostylus elongate, length 0.179 mm, width 43 μm (Figures 11.1, 11.2). Gonocoxite apex with possibly two or three spiniform structures, the largest and basalmost 63 μm long, 15 μm wide at base, not preserved / visible on right gonocoxite. Gonocoxite with large basal lobe, tip spiniform. Female unknown.	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFE69B43FF60FABD25F6FE7A.taxon	discussion	Remarks Given the demonstrably unreliable criteria for identification of adult Dixidae at the generic level (see Discussion), the option of designating the four fossil specimens described herein as “ Dixidae incertae sedis ” was considered. However, given 1) our desire to distinguish these four species from all fossil dixids described previously and 2) the observation that designations such as “ Genus incertae sedis ” or “ Genus indeterminate ” are often not recorded in commonly used databases, a generic designation has been provided. The four new species described herein are assigned to the genus Dixella, not necessarily based on morphological criteria, but rather on the near-shore lacustrine environment in which they lived and were deposited (Greenwalt et al., 2015; see Discussion). This of course presumes that genus-specific ecological niches (fast-flowing waters in the mid-stream of waterways or water falls [Dixa] vs. still waters of near-shore lake or pond environments [Dixella] [Nowell, 1951]) had already been established 46 Ma. Specific characteristics, in various combinations, used to distinguish the four fossil Nearctic species from all other dixid genera both extant and extinct, other than Dixa and Dixella, are as follows (with number of species given in parentheses): Syndixa (3): R 2 fused with R 1 (Lukashevich, 1996); Eucorethrina (3): R 1 equidistant from C and R 3 (R 2 in Peters and Cook [1966]) and Sc ending distad of Rs origin (Lukashevich, 1996); Asiodixa Papp et al., 2006 (2): small size (wings 2.0 – 2.5 mm) and Sc ending substantially before the Rs origin, Rs sigmoidal, F 1 of male with a ventromedial dilation (Papp et al., 2006); Neodixa Tonnoir, 1924 (1): R 2 + 3 unbranched (Belkin, 1968); Nothodixa (10): first flagellomere oval, its length equal to or less than 2.5 x its width (Belkin, 1968); Metadixa Peters and Savary, 1994 (1): known only from a single larval specimen (Peters and Savary, 1994); Mesodixa Belkin et al., 1970 (1): F 1 longer than F 2 + F 3, gonostylus longer than gonocoxite, curved, spinose and small size (wing 2.5 mm) (Belkin et al., 1970); Meringodixa Nowell, 1951 (1): large spatulate ventral process of gonocoxite, F 1 fusiform and 6 x as long as wide, head and thorax brown and brownish yellow, respectively, stem of haltere yellow and dorsum of abdomen black (Nowell, 1951). The Cenozoic dixids consist of nine species including the four described herein as well as two designated as incertae sedis (Table 2). A comparison between these is impeded by deficiencies in the published descriptions of the European fossils. Both Dixa priscula and D. cimbrica Ansorge, 1992 were described from isolated wings and, given the variability in wing venation in this family, can only be identified as members of the family Dixidae (see below). Dixa tertiaria Meunier, 1915 was originally described as a member of the family Limoniidae and, although the fossil is of an intact adult, no relevant information was provided other than a very low-resolution photograph and scale bar (Meunier, 1915). Theobald (1937) described Dixa hyalipennis Theobald, 1937 as having venation identical to D. tertiaria and synonymized the two species; Evenhuis (1994) synonymized both under D. tertiaria. However, comparison of Theobald’s figure and Meunier’s photograph clearly shows numerous differences in wing venation. Theobald’s depiction of the first abscissa of CuA 1 portrays a vein unlike that in any other species of dixid; the distal half of this vein segment is parallel with vein M and forms a smooth continuous curve with the distal portion of CuA 1. Meunier’s photograph depicts the first abscissa of CuA 1 as straight and at a distinct angle to the second abscissa, in a fashion similar to all other dixids. Descriptions of genitalia are not provided and, in fact, neither specimen is identified as to its sex. Similarly, the genitalia of Dixa succinea were not visible in the original specimen described by Meunier (1906) although it was described as male (mistakenly identified as female in the figure legend). Because the type specimen of Dixa succinea has been lost, Hennig (1966) designated and described a neotype and figured its genitalia as well as those of Dixella filiforceps, D. distans and Dixa minuta Meunier, 1906, all males. Unfortunately, Hennig’s descriptions of Dixa succinea, Dixella filiforceps and D. distans were otherwise purposefully very brief – no measurements were made – as he believed that “ A detailed description of this and the following species would have little meaning. In order to clarify their position within the Paradixinae (Dixella), the extant species must first be carefully worked through. ” All four of the Nearctic fossil dixids are distinguished from Dixa minuta and Dixella distans in that these specimens, both Baltic amber inclusions, are much smaller in size with wing widths less than 0.6 mm (Cockerell, 1921; Hennig, 1966). Although both Dixa priscula and Dixa cimbrica are herein declared nomina dubia (See Discussion), differences in venation between them and the four Nearctic fossils are as follows: Dixa cimbrica differs from Dixella eomarginata in that Sc originates at the origin of Rs, Rs forks basal of r-m, and m-cu originates basal of r-m; from Dixella spinilobata in that Sc originates at the origin of Rs; from Dixella curvistyla in that M 1 + 2 is longer than M 1, and m-cu originates basal of r-m; from Dixella intacta in that m-cu originates basal of r-m. Dixa priscula differs from Dixella eomarginata in that Sc originates basal of Rs, and m-cu originates basal of r-m; from Dixella spinilobata in that Sc originates basal of the origin of Rs; from Dixella curvistyla in that M 1 + 2 is longer than M 1, m-cu originates basal of r-m, and Sc originates basal of the origin of Rs; from Dixella intacta in that m-cu originates basal of r-m and Sc originates basal of the origin of Rs. Dixella eomarginata and D. intacta differ from all other fossil dixids in being female. Dixella eomarginata differs from all other fossil dixids in having the posterior margin of the wing slightly emarginate between CuA 1 and CuA 2 – similar to the extant Dixella marginata. The prominent apparent false vein between M and Cu that continues between M 1 + 2 and CuA 1 in the left wing of D. eomarginata may be an artifact, possibly a result of partial delamination of the wing; it does not appear in the right wing. This character is not common in the ‘ Nematocera’ but it is found, between M 2 and CuA 1, in both Scatopsidae (Coboldia Melander, 1916) and several genera of Simuliidae (McAlpine et al., 1981). A false vein parallel to and just posterior of Cu and CuA 2 was described in Dixa appalachiensis (Moulton, 2016). While the male of Dixella marginata lacks the emarginate (excavate) wing margin of the female (Peters and Cook, 1966), there is no evidence for or against Dixella eomarginata being conspecific with either D. curvistyla or D. spinilobata. The body and wing lengths of Dixella intacta are 34 % and 48 % longer than those of D. curvistyla and 29 % longer than D. spinilobata, respectively. Males and females of a given species can vary in size, females commonly with larger wing and body lengths, but the relationship is not consistent (e. g., wing lengths in males of both Dixella fraxina Taber, 2010 and D. indiana Dyar, 1925 are often larger than in the female) (Takahasi, 1958; Peters and Cook, 1966; Taber, 2010). Because wing and body lengths within a single sex of a species can vary as much as 50 % (Takahasi, 1958; Peters and Cook, 1966), differences in wing and body lengths alone do not preclude Dixella intacta from a conspecific relationship with D. spinilobata or D. curvistyla. However, given the absence of any analysis of female genitalia relative to the definition of the genera Dixa and Dixella, the variability in wing venation patterns between these two genera and within individual species (see below and Discussion), and the dearth of morphological detail available for the European fossils, it would be speculative to depict Dixella intacta as congeneric with any other known fossil male dixid. The male Nearctic fossil species, Dixella curvistyla and D. spinilobata, are distinguished from those of D. succinea, D. filiforceps, and D. distans based on the shape of the gonocoxite and gonostylus. The gonocoxite of D. succinea is short relative to the gonostylus, the latter tapered distally with the terminal quarter of the stylus bent at a right angle to the base, approximately 150 μm long and less than 20 μm wide at mid-length. The apical lobe of the gonocoxite is long and narrow (about 75 μm x 10 μm). The gonostylus of D. filiforceps is very long and narrow (approximately 225 μm long and less than 20 μm wide), slightly widened at the end, and smoothly curved such that the distal half is at a right angle to the base. The apical lobe of the gonocoxite is long and narrow (about 10 μm x <10 μm). The gonocoxite of D. distans is short relative to the gonostylus and, like D. filiforceps, the gonostylus is long and narrow (approximately 125 μm long x 20 μm wide) and smoothly curved. Unlike in D. filiforceps, the gonostylus is tapered to an asymmetrical point at the end. The apical lobe of the gonocoxite is long and narrow (about 75 μm x <10 μm). These characteristics contrast with D. curvistyla in which the gonostylus is relatively short and wide (approximately 158 μm x 79 μm at its base) and bent at a near right angle and the apical lobe of the gonocoxite is quite wide (approximately 24 μm). In contrast, D. spinilobata has a straight and relatively wider rectangular gonostylus (179 μm x 43 μm) with a relatively shorter apical lobe (0.35 x the length of the gonostylus vs. ratios of 0.5 – 0.6 for the three specimens described by Hennig (1966 )). Dixa tertiaria is problematic in that the original description (Meunier, 1915) is essentially devoid of useful information and no redescription has so far been produced. A photograph and a scale bar is provided and enables body (3.2 mm) and wing (2.8 – 3.2 mm) lengths to be determined, albeit with a degree of uncertainty. These measurements contrast with those of Theobald (1937), who described Dixa hyalipennis with a body length significantly shorter than the wing length (3.7 mm and 4.2 mm respectively). All of the Nearctic fossils have body / wing length ratios greater than one. As described above, the very peculiar morphology of vein CuA 1, as figured by Theobald (1937), also differentiates these two specimens. Without examination of the actual specimens, it is impossible to accurately compare them with the Nearctic dixids. It is difficult to compare Dixella intacta and D. eomarginata with extant dixids of the genera Dixa and Dixella as there exists neither detailed nor extensive studies of female genitalia with respect to the taxonomy of these two genera. Some keys to females of this family exist (e. g., Disney, 1975 - which does not use genitalic characters to distinguish between genera) but they are of limited use. The structure of the genitalia of D. intacta is very similar to that of Dixa brevis as figured by Nowell (1951). The very broad and acutely curved gonostylus of Dixella curvistyla resembles that of Dixa formosana Papp, 2007 although the latter has a very short apical lobe on the gonocoxite (Papp, 2007). Dixa neohegemonica, with a sickle / fingershaped gonostylal apex, also resembles D. curvistyla (Moulton, personal obs.); note that this structure is figured as straight in Peters and Cook (1966). The genitalic morphology of Dixella spinilobata is unique amongst extant members of this	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFF69B4AFE63FED22324FDA8.taxon	description	Dixa babai Dixa brevis Dixa californica	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFF69B4AFE63FDAF2324FA58.taxon	description	Dixa clavata Dixa dilatata Dixa dyari Dixa fluvica Dixa fusca Dixa hegemonica Dixa hikosana Dixa hoffmani Dixa inextricata Dixa johannseni Dixa kaplani Dixa kyushuensis Dixa lobata Dixa lobatus Dixa longistyla Dixa lunata Dixa maculata Dixa melanderi Dixa minuta † Dixa minutiformis Dixa modesta Dixa modesto Dixa naevia Dixa nebulosa Dixa neoaliciae	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFF69B49FE63F9BF232FFBE7.taxon	description	Dixa notata Dixa nova Dixa nubilipennis Dixa obtusa Dixa orientale Dixa priscula † Dixa puberula Dixa punctata Papp et al., 2006 WRBU Takahashi, 1958 WRBU WRBU WRBU Ansorge, 1992 WRBU WRBU WRBU WRBU WRBU WRBU Takahashi, 1958 WRBU WRBU WRBU Wagner et al., 1991 / 1992 Takahashi, 1958 WRBU WRBU Takahashi, 1958 WRBU WRBU WRBU Hennig, 1966 Takahashi, 1958 Johannsen, 1923 WRBU WRBU WRBU WRBU WRBU Takahashi, 1958 WRBU Peters, 1981 WRBU Takahashi, 1958 WRBU Cockerell, 1921 Disney, 1975 Wagner et al., 1991 / 1992 Taxon Reference / Depository Dixa rathyme WRBU Dixa serrata Dixa serrifera Dixa similis Dixa spiralis Dixa stuckenbergi Dixa submaculata Dixa subobscura Dixa terna Dixa tertiaria † Dixa trilineata Dixa xavia Dixa yamatona Dixella aegyptiaca Dixella aestivalis Dixella amphibia Dixella attica Dixella aurora Dixella autumnalis Dixella corensis Dixella cornuta Dixella curvistyla † Dixella deltoura Dixella distans †	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFF59B49FE63FBC8231EF8AD.taxon	description	Dixella filiforceps † Dixella fraxina Dixella fuscifrons Dixella fuscinervis Dixella golanensis Dixella hansoni Dixella hernandezi Dixella indiana Dixella intacta † Dixella israelis Dixella jironi Dixella laeta Dixella limai Dixella lobata Dixella maculata Dixella martini	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFF59B4EFE63F8A8242BFECA.taxon	description	Dixella obscura WRBU WRBU WRBU WRBU WRBU WRBU Takahashi, 1958 WRBU Theobald, 1937 Takahashi, 1958 WRBU Takahashi, 1958 Wagner et al., 1991 / 1992 WRBU Disney, 1975 Wagner et al., 1991 / 1992 WRBU WRBU Peters, 1992 WRBU This study WRBU Hennig, 1966 This study Chaverri and Borkent, 2007 Disney, 1975 Hennig, 1966 Taber, 2010 Wagner et al., 1991 / 1992 WRBU Wagner et al., 1991 / 1992 Chaverri and Borkent, 2007 Chaverri and Borkent, 2007 Peters and Cook, 1966 This study Wagner et al., 1991 / 1992 Chaverri and Borkent, 2007 Peus, 1936 WRBU Chaverri and Borkent, 2007 Chaverri and Borkent, 2007 WRBU Belkin, 1968 Peters, 1980 WRBU APPENDIX 2. Character states used in the analysis of fossil and extant dixid wing venation. 1. Vein Sc apex relative to the origin of Rs: basal [> 2 X vein width] (0); subbasal [<2 X vein width] (1); even (2); subapical [<2 X vein width] (3); apical [> 2 X vein width] (4). 2. Crossvein r-m origin relative to the bifurcation of Rs: basal (0); subbasal [<2 X vein width] (1); even (2); subapical [<2 X vein width] (3); apical (4). 3. Crossvein m-cu origin relative to the terminus of r-m: basal (0); subbasal [<2 X vein width] (1); even (2); subapical [<2 X vein width] (3); apical (4). 4. Vein A 1 terminus relative to the origin of Rs: basal (0); subbasal [<2 X vein width] (1); even (2); subapical [<2 X vein width] (3); apical (4). 5. Vein A 1 terminus relative to Sc terminus: basal (0); subasal [<2 X vein width] (1); even with (2); subapical [<2 X vein width] (3); apical (4). 6. Vein A 1 terminus relative to the bifurcation of Cu: basal (0); subbasal [<2 X vein width] (1); even (2); subapical [<2 X vein width] (3); apical (4). 7. Vein R 2 + 3: branched (0); unbranched (1). 8. R 2 + 3 curvature: straight or very slightly arched (0); strongly arched (1). 9. Vein R 2 + 3 branch relative to the bifurcation of M: basal (0); subbasal [<2 X vein width] basal (1); even (2); subapical [<2 X vein width] (3); apical (4). 10. Vein R 1: fused to C far basal (near 3 / 4 wing length) of wing apex (0); closer to C than R 2 and fused near wing apex (1); equidistant to C and R 2 and fused near wing apex (2). 11. Vein R 2: not fused with R 1 (0); fused with R 1 (1). 12. Rs: straight (0); sigmoidal (1). 13. Wing length / width: <2.5 (0); 2.5 – 3 (1);> 3 <4 (2)> 4 (3). APPENDIX 3. Morphological data matrix (Dixidae wing and venation characters only). Taxon 1 2 3 4 5 6 7 8 9 10 11 12 13 Dixa aliciae 2 1 2 2 2 0 0 1 4 1 0 0 -	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFF29B4DFF44F880242BFF4D.taxon	description	4 4 2 4 4 4 4 4 4 4 4 4 4 2 4 4 4 0 4 4 4 4 2 4 4 4 4 4 4 4 2 4 4 4 2 4 4 3 4 2 4 0 0 1 0 1 0 0 1 4 0 0 1 0 1 0 0 0 4 0 0 1 2 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 3 1 0 0 - 4 0 0 1 4 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 2 1 0 0 - 4 0 0 1 0 1 0 0 1 4 0 0 1 4 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 3 1 0 0 1 4 0 0 1 4 1 0 0 1 4 2 0 1 0 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 4 1 0 0 1 4 0 0 1 4 1 0 0 - 4 0 0 1 4 1 0 0 - 4 0 0 1 4 1 0 0 - 4 2 0 1 0 1 0 0 1 4 0 0 1 0 1 0 0 2 3 0 0 1 4 1 0 0 - 4 0 0 1 4 1 0 0 - 4 0 0 1 2 1 0 0 - 4 1 0 1 4 1 0 0 - 4 0 0 1 2 1 0 0 - 0 0 0 1 4 1 0 0 1 4 0 0 1 0 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 0 1 0 0 1 4 0 0 1 4 1 0 0 - 4 1 0 1 2 1 0 0 1 4 0 0 1 2 1 0 0 2 4 1 0 1 1 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 3 1 0 0 - 4 0 0 1 2 1 0 0 - 4 0 0 1 0 1 0 0 - Taxon 1 2 3 4 5 6 7 8 9 10 11 12 13 Dixa stuckenbergi 0 0 4 1 4 0 0 1 4 1 0 0 -	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
0393156CFFF19B4DFF44F88F242BF8DD.taxon	description	4 4 4 4 4 4 4 - 3 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 2 4 4 4 4 4 0 4 4 4 4 4 4 0 0 1 4 1 0 0 - 4 0 0 1 0 1 0 0 1 4 0 0 1 0 1 0 0 - 4 2 0 1 4 1 0 0 1 4 0 0 1 4 1 0 0 - 4 1 0 1 2 1 0 0 1 4 0 0 1 0 1 0 0 2 4 2 0 1 4 1 0 0 0 - - 0 1 4 1 0 0 1 4 1 0 1 4 1 0 0 2 4 0 0 1 2 1 0 0 2 4 0 0 1 0 1 0 0 - 4 0 0 1 1 1 0 0 1 4 0 0 1 4 1 0 0 0 4 0 0 1 0 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 1 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 0 1 0 0 1 4 2 0 1 1 1 0 0 0 4 0 0 1 0 1 0 0 1 4 0 0 1 0 1 0 0 1 4 0 0 1 0 1 0 0 - 4 2 0 1 4 1 0 0 1 4 0 0 1 1 1 0 0 1 3 0 0 1 1 1 0 0 1 4 0 0 1 0 1 0 0 2 4 4 0 1 0 1 0 0 2 4 0 0 1 0 1 0 0 1 4 0 0 1 2 1 0 0 - 4 0 0 1 0 1 0 0 - 4 0 0 1 - 1 0 0 1 0 0 0 1 2 1 0 0 1 4 0 0 1 4 1 0 0 - 4 0 0 1 0 1 0 0 2 4 0 0 1 4 1 0 0 1 4 0 0 1 4 1 0 0 2 4 0 0 1 0 1 0 0 - 4 0 0 1 2 1 0 0 1 4 2 0 1 4 1 0 0 - 4 0 0 1 0 1 0 0 2 4 1 0 1 0 1 0 0 1 0 0 0 1 0 1 0 0 1 4 0 0 1 2 1 0 0 -	en	Greenwalt, D (2016): The first fossil New World Dixidae with a critical discussion of generic definitions. Palaeontologia Electronica 19 (3): 1-32, DOI: 10.26879/656, URL: http://dx.doi.org/10.26879/656
