PLATYPEZIDAE

Grimaldi, David A., 2018, Basal Cyclorrhapha In Amber From The Cretaceous And Tertiary (Insecta: Diptera), And Their Relationships: Brachycera In Cretaceous Amber Part Ix David A. Grimaldi, Bulletin of the American Museum of Natural History 2018 (423), pp. 1-97 : 1-97

FAMILY PLATYPEZIDAE

Platypezidae is a small family of only about 250 Recent species worldwide, most of which are quite rare, represented in museum collections by only a few specimens. In an intensive survey of a montane tropical forest in Costa Rica, for example, among the 100,000 or so specimens processed and more than 4200 fly species found, none were Platypezidae ( Brown et al., 2018; Borkent et al., 2018). Systematics of the group is well established, with major contributions to the world fauna by E.L. Kessel and by P.J. Chandler (e.g., Chandler, 1994; 2001). Chandler (2001) presented a comprehensive phylogenetic scheme for the genera based on adult and larval morphology and reviewed the biology and natural history of Platypezidae in detail. Those genera whose hosts are known mostly breed in fleshy macrofungi, especially mushrooms; Agathomyia forms galls in bracket fungi. Larvae are stout, broad, somewhat flattened, with each segment usually having pairs of tubercles (lateral pairs can be annulated, fringed, or otherwise elaborate in some taxa). Males are holoptic, have a larger anal lobe, and they swarm, which is how many species are found. The striking color patterns—com-monly with iridescent, reflective patches on a velvety black or brown cuticle—are clearly used for signaling while swarming.

As presently recognized ( Chandler, 2001) there are four subfamilies: the basal Microsaniinae plus Melanderomyiinae , and two sister groups that comprise most of the species, Callomyiinae + Platypezinae . The Palearctic genus Opetia Meigen is now placed in a separate family, Opetiidae , along with the recently discovered Chilean genus Puyehuemyia Amorim et al. (2018) . Within Microsaniinae , the worldwide genus Microsania Zetterstedt is well known for being attracted to smoke (reviewed in Chandler, 2001; see also Klocke et al., 2011), although the breeding sites of these flies remain unknown. Melanderomyiinae is monotypic, consisting of Melanderomyia kahli Kessel from eastern North America, which breeds in stinkhorn fungi (Phal- lales). Chandler (2001) proposed six morphological characters to link Microsania and Melanderomyia ; the molecular phylogeny of Tkoč et al. (2017) proposed that Melanderomyia is the sister group to Callomyiinae plus Platypezinae . In most other respects, though, the phylogenetic relationships in both studies agree.

Although Platypezidae are uncommon as fossils, there appears to be a significant, extinct phylogenetic diversity of these flies, especially from the Cretaceous. In fact, Mostovski (1995a) reported a surprising diversity and abundance of compression-fossil Platypezidae from several Cretaceous sites in Eurasia, most specimens of which I have restudied (these are housed in the Paleontological Institute, Moscow). Zhang (1987) described compression-fossil Platypezidae from China (originally reported as Jurassic, now known to be Early Cretaceous). As Mostovski (1995b) mentioned—which I can confirm here for several

TABLE 2

Characters in the cladogram for Platypezidae (fig. 27)

1. Wing shapes sexually dimorphic, male with large anal lobe.

2. Sc vein short, less than 0.3× wing length.

3. Cell cup very small, barely extended beyond apex of cell bm.

4. Anal lobe of female very narrow.

5. Crossvein dm-cu (cell dm) absent.

6. Aristal portion of antenna thick, 3-articled.

7. Terminal segment of female abdomen piercing.

8. Eyes setulose.

9. Vein C not circumambient, ends at apex of M 1.

10. Length of fork of M 1 -M 2 less than or equal to length of stem.

11. Acrostichals reduced to 0, 1, or 2 rows.

12. Proscutellum lost.

13. Acrostichals reduced to uniserial row or lost entirely, dorsocentrals in pair of graded rows.

14. Vein R 1 relatively short.

15. M veins reduced (bases or branches lost, or weakly developed).

16. Basal flagellomere short, stout, subcircular or reniform.

17. Clypeus inflated, face bulging in females.

18. Setae on anal lobe and alula flattened.

19. M not forked (vein M 2 lost).

20. Sclerotized portion of vein C ends at apex of R 1, thick, with large spinules.

21. M 1 basally incomplete.

22. Pterostigma present, large, between Sc and R 1 and distal to apex of R 1

23. Metabasitarsomere 1-2 or 3 expanded, tarsomere 1 longest on leg.

24. More than one metatarsomere expanded in both sexes.

25. Small, dark, sclerotized, bifid scales on tarsi and portions of tibiae (first reported by Comstock and Comstock, 1904 [p. 474: fig. 579], contra Tkoč et al., 2016).

26. Crossvein dm-cu close to wing margin, separated by distance ≤2× length of dm-cu, often much closer) (cell dm-cu very long).

27. CuA2 straight, forming side of slender, acute triangle of cell cup.

28. Male profemur with posteroventral oxhorn seta.

29. Male metafemur with large posteroventral seta near base.

30. Metabasitarsomere short, less than length of 2+3+4.

31. Acrostichals absent.

32. Female without fronto-orbital or interfrontal setae.

33. Third metatarsomere longer than first.

34. Gena, parafacial areas bare.

in amber (i.e., Paleopetia Zhang)—some of Zhang’s genera are in fact Ironomyiidae , not Platypezidae . The typical preservation in these compression fossils is of isolated wings, so venation is the primary source of characters, but in exceptional circumstances there are also preserved wing microtrichia and some body features (e.g., flattened hind tarsomeres, personal obs.). Unfortunately, critical details are never preserved of acrostichals, dorsocentrals, genitalia, bifid scales and other small structures of the legs, etc., so interpretation of these compression fossils is quite limited. Until now the only platypezid in amber from the Cretaceous (Turonian: New Jersey) has been Electrosania cretica Grimaldi and Cumming (1999) . Chandler (2001) suggested that Electrosania might be an opetiid based on the numerous acrostichals (its single basal aristomere is also unique for the family), but in the cladogram of basal platypezids presented here (fig. 27), Electrosania is one of two basalmost stem group genera for the family. In the present work I am reporting four additional platypezid genera and species from the Cretaceous, all in amber.

Surprisingly, fossil Platypezidae have been even rarer in the Tertiary, despite the richer deposits from this geological era. Cockerell (1909, 1911) described two platypezids from the late Eocene shales of Green River and Florissant, and the only platypezid described from the vast deposits of Baltic amber is the controversial Oppenheimiella baltica (Meunier) , of uncertain family placement since the original description is ambiguous and the type lost. Microsania is newly reported herein from Baltic amber, along with two species of Lindneromyia in Miocene amber from the Dominican Republic.

A phylogenetic hypothesis of relationships for some extinct and basal extant genera of Platypezidae is presented in figure 27, based on 54 morphological characters (see table 2). Fossils in the phylogeny are represented only by genera preserved in amber. There is a grade of Cretaceous genera basal to Callomyiinae and Platypezinae , as well as three Cenozoic fossils in living genera ( Microsania in Baltic amber, and two species of Lindneromyia in Dominican amber). Further, a stem-group genus to Melanderomyia + Microsania occurs in Early Cretaceous amber from Lebanon. The most surprising discovery is a crown-group platypezine in Burmese amber, Chandleromyia , n. gen.