ARCHISARGOIDEA, Rohdendorf, 1962

Grimaldi, David A. & Barden, Phillip, 2016, The Mesozoic Family Eremochaetidae (Diptera: Brachycera) in Burmese amber and Relationships of Archisargoidea: Brachycera in Cretaceous Amber, Part VIII, American Museum Novitates 2016 (3865), pp. 1-32 : 10-13

RELATIONSHIPS IN ARCHISARGOIDEA

In the character descriptions below those states indicated by a “0” are plesiomorphic (based on comparison to various outgroup orthorrhaphans); states “1” or higher are derived.

CHARACTERS AND DESCRIPTIONS

BODY FORM

1. Thorax compact, short but deep; abdomen long, slender, and cylindrical in both sexes, abdomen comprising ≥ 0.60× combined length of thorax of abdomen (figs. 1A, 4). These two features were not separated because they seem to always co-occur in Diptera , in various nematocerans and assorted Brachycera (e.g., leptogastrine Asilidae , systropine Bombyliidae , Evocoidae , Vermileonidae , etc.). The abdomen is sexually slightly dimorphic in Tethepomyiidae , with the one known female having a somewhat shorter, stouter abdomen (e.g., Grimaldi et al., 2011: Tethepomyia zigrasi ). Based on a few other archisargoids where both sexes are known (e.g., Alleremonomus xingi [J.-F. Zhang, 2014a: fig. 4]) there otherwise doesn’t seem to be dimorphism in body shape.

HEAD

2. Shape: spherical or subspherical, with eyes large and occupying much of head surface (fig. 1B, C) (vs. hemispherical, or slightly dorsoventrally flattened, with eyes occupying largely just lateral surfaces of head capsule).

3. Head hemispherical, with eyes in both sexes occupying virtually all of lateral and much of dorsal surfaces (and replacing most of occiput in males).

4. Eyes with facial margins very close or medially contiguous (e.g., figs. 1C, 3A); at least the male is holoptic (e.g., Tethepomyiidae ) and sometimes both sexes (e.g., Alleremonomus xingi [J.-F. Zhang, 2014]).

5. Position of antennal articulation: situated distinctly dorsally, and close to the ocellar triangle (e.g., figs. 1B, 3B) (vs. frontally near anterior margin of frons, or ventrally above clypeus). This is one of the defining features of Archisargoidea , fortunately well preserved in various lithified genera. The antennae in Tethepomyiidae are not dorsally situated.

6. Antennal size and shape: small, with postpedicel having a drop-shaped base and produced apically into a slender, style- or aristalike projection (figs. 2B, D, 3C). The excellent preservation of Zhenia reveals at 400× that there is a minute apical article on the postpedicel (fig. 3C), which corresponds to the true stylus. The pedicel is a typical cone-shaped segment in Archisargoidea . The postpedicel in the Tethepomyiidae is unique (char. 7).

7. Structure of postpedicel: reduced to a U-shaped or crescentic article. Found only in Tethepomyiidae . It is possible that a minute style or terminal antennal article is nestled within the postpedicel cavity, but this has not been observable.

8. Mouthparts: vestigial, with theca and labellum either lost or so vestigial as to be unobservable. Found in those Tethepomyiidae where the mouth region is observable; at least in Tethepomyia thauma Grimaldi and Cumming (in New Jersey amber) the palpi are present (and 1-segmented), though very small, and the other mouthparts appear absent or highly vestigial.

WING

9. General shape: width to length ratio (i.e., thickness of wing blade), a continuously quantitative character. Wings vary from long and slender (0.21) (e.g., fig. 5A) to short and broad (0.42) (e.g., fig. 6D).

10. Venation highly reduced: longitudinal veins apically incomplete/evanescent (complete in Tethepomima ); veins R 1 and Rs are thick and sclerotized, but simple (unbranched) in Tethepomyia and 2-branched in Tethepomima .

11. R veins crowded (parallel and very close for most of their length), especially R 1 and R 2+3, a condition found in Kovalevisargidae (fig. 5C).

12. Relative length of stem Rs measured as a proportion of the total length of Rs. A continuously quantitative character varying from a very short stem (0.05, in Mesosolva zhangi [not coded in matrix]) to one approximately one-third the total length of Rs (0.33, in Daohugosargus eximius ).

13. R 2+3 fused with anterior border of cell d, arising from cell d ( Lepteremochaetus , Dissup : fig. 6B, D) or even basal to it ( Alleremonomus ).

14. Tip of R 2+3 upturned and converging very close to tip of R 1 or actually meeting it, found in Archisargus spp. (fig. 5A), as well as in some beridine and other Stratiomyidae .

15. Tip of R 2+3 meeting and fused with R 1 well before tip of R 1; found only in Calosargus spp. and Zhenia (see also character 16) (fig. 6C, E).

16. R 2+3 very short, meeting R 1 well before tip of R 1 (for a length ≥ length of R 2+3): found in Alleremonomus , Dissup , and Lepteremochaetus (fig. 6B, D).

17. Stem of R 4+5 connected to apex of cell dm, as found, e.g., in Alleremonomus , Dissup , Eremochaetus , Eremomukha , and Lepteremochaetus (fig. 6).

18. Fork of R: small, branches asymmetrical, with anterior branch significantly shorter (fig. 6A–D) (vs. fork longer, symmetrical or nearly so, with tips encompassing tip of wing). A strongly asymmetrical fork occurs in beridine and many higher stratiomyids, but the fork is not particularly short or small. A longer, symmetrical fork in most other archisargoids suggests that the asymmetry in archisargoids and stratiomyids is convergent.

4+5

19. Fork of R 4+5 absent or lost, found only in Kovalevisargidae among the taxa that were studied here (fig. 5C).

20. Width of cell dm in proportion to its length (i.e., thickness). A continuously quantitative character varying from stout (width 0.54× the length— Eremomukha addita ) to long and slender (width 0.13× the length— Orientisargus illecebrosus , Kerosargus argus ).

21. Length of cell bm relative to that of cell br. A continuously quantitative character varying from cell bm significantly shorter than br (0.69, in Daohugosargus eximius ) to longer than cell br (1.29, in Kerosargus argus ).

22. Position of r-m crossvein relative to length of cell dm. A continuously quantitative character varying from very close to the base of cell dm (0.05, in Orientisargus illecebrosus ) to three-quarters the length of cell dm (0.77, in Origoasilus pingquanensis ).

23. Cell m 3 is closed before the wing margin (M 4 is joined to M 3) (figs. 5D, E; 6D) (vs. cell open, these M veins not joined before the wing margin). In Archisargoidea cell m 3 occurs in Alleremonomus , Archisargus strigatus , Dissup , Mesosolva (including species formerly placed in Brevisolva and Prosolva ), Orientisargus , Origoasilus , and Parvisargus malus . In other Brachycera cell m 3 also occurs in some Acroceridae , Apioceridae , many Asilidae , Nemestrinidae , some Therevidae and Xylophagidae , Xylomyidae , and in Vermileonidae .

24. Apical branches of vein M: 2 (M 3 is lost) (fig. 5B) (vs. 3 branches). Found in Calosargus (except C. thanasymus Mostovski ), Eremomukha tsokotukha , Flagellisargus , and Sharasargus .

25. Vein M: simple, unbranched in all Tethepomyiidae .

26. Cell cup is closed (i.e., CuA 2 and A 1 meet before the wing margin) (figs. 5A; 6A, C, D), vs. open.

27. Cell br with longitudinal spurious vein (e.g., fig. 5D). This vein was mentioned by Ren and Guo (1995) and K.-Y. Zhang et al. (2007a), but not reported in descriptions by J.-F. Zhang (though indicated in some drawings, e.g., Tabanisargus , Archirhagio mostovskii ). There are some discrepancies among descriptions and images, e.g., Mesosolva sinensis has a spurious vein according to J.-F. Zhang (2010) but not according to the original description by K.-Y. Zhang et al. (2010a). A spurious vein is not reported in Mesosolva huabaiensis (Hong) by J.-F. Zhang (2015) but is visible in the photo in that paper.

28. Vein CuA or CuA 2 +A 1 (originally interpreted as CuA-CuP [ Grimaldi and Cumming, 1999]): apically forked in Tethepomima holomma Grimaldi and Arillo , Tethepomyia buruhandi Grimaldi and Arillo , and Tethepomyia zigrasi Grimaldi and Arillo (not visible for T. thauma ).

29. Anal lobe is lost or highly reduced, measured as the width of the anal lobe as a proportion of the overall width of the wing, a continuously quantitative character. This feature is found in most Archisargoidea , where it is preserved (the anal lobe margin was not preserved in 13 lithified species). Tethepomyia zigrasi has a reduced anal lobe, although the other three species of tethepomyiids have a well-developed anal lobe.

30. Base of wing: petiolate, long, and slender (fig. 6A–C). To some extent this is correlated with the character above (anal lobe highly reduced), but not entirely the same. Found in Eremomukha , Lepteremochaetus , and Zhenia .

ABDOMEN AND TERMINALIA

31. Abdomen extremely long, slender, and cylindrical; abdomen is ≥0.80× combined length of thorax + abdomen (cf. char. 1) (figs. 1A, 4).

32. Oviscapt: Three conditions are scored: 1. Formed from elongate cerci. In Recent orthorrhaphans this condition is found in several genera of Nemestrinidae ( Hirmoneura , Neorhynchocephalus , Trichopsidea ), but the cerci are not pointed at the tips nor are they rigid and heavily sclerotized. 2. The base of the oviscapt is bulbous and the sharp tips of the cerci (aculeus) point posteriad, which is seen in most archisargoid females whose terminalia are preserved (including Zhenia ) (figs. 2E, F, 3D), exceptions being Orientisargus illecebrosus and Uranorhagio (J.-F. Zhang, 2012a). 3. Oviscapt base not particularly bulbous, and the oviscapt (which includes at least the cerci) is curved ventrad. This condition (3) occurs in Tethepomyia zigrasi , the only species of tethepomyiid whose female is known. It needs to be noted that a similar, ventrally hooked structure was reported in the compression fossil Kovalevisargus haifanggouensis , but which was interpreted as male genitalia (J.-F. Zhang, 2014a). Kovalev (1986) indicated that the aculeate female terminalia define the Eremochaetidae , but this distinctive character has been found since then to be more widespread among Archisargoidea . Mostovski (1997) mentioned an undescribed species/specimen of Archocyrtidae with a “needlelike ovipositor,” which if verified would place this family also within the Archisargoidea .