Rhipidoxylomyia rasnitsyni, Szx, 2021

Szx, André Nel, 2021, New Cecidomyiidae from the Lowermost Eocene French amber (Diptera), Palaeoentomology 4 (6), pp. 620-628 : 623-626

(?) Rhipidoxylomyia rasnitsyni sp. nov.

( Figs 3–5 )

urn:lsid:zoobank.org:act:7B98E607-17F1-4580-9958-2F5F3C55199A

Material. Holotype MNHN.F. A71373 (PA 12413 1/2, female, in the same piece of amber with a Hymenoptera Chalcidoidea), deposited in the Département Histoire de la Terre, Muséum national d’Histoire naturelle, Paris, France.

Etymology. Named after Professor Alexander Rasnitsyn, for his impressive contribution to the study of extant and fossil insects.

Diagnosis. Female characters only. 12 flagellomeres, each with four sensoria with two forks; ocelli absent; basal tarsomeres short; R with only two branches; M1+2 absent; distal part of M4 present but basal part strongly reduced; CuA1 absent.

Description. Female ( Fig. 3 ). Head 0.3 mm long, 0.25 mm high; eyes with a narrow dorsal bridge, 0.05 mm wide, touching in one point; ocelli absent; antenna 0.8 mm long, scape 0.05 mm long, pedicel 0.15 mm long, 12 flagellomeres, of nearly the same size, all longer than wide (0.05 mm long) with neck inconspicuous, flagellomeres with four translucent sensoria with two forks, no circumfila, no band-shaped sensorium ( Fig. 4 ), palpus with four segments of nearly the same length. Thorax 0.3 mm long, longer than broad.

Wing ( Fig. 5 ) 1.0 mm long, 0.5 mm wide, hyaline, macropterous, wing membrane with microtrichia, wing margin with numerous long macrotrichia; antC and R5 confluent; humeral vein absent; subcostal vein very close to R, incomplete, 0.2 mm long, not reaching wing margin; vein R1 0.2 mm long; R5 simple, emerging from R 0.4 mm from wing base; part of Rs basal of crossvein r-m very short (0.02 mm long); M1+2 absent; M4 present but not connected to base of M; CuA simple; CuP absent.

Haltere with large knob, 0.06 mm wide and 0.2 mm long, and stem 0.1 mm long, bare.

Legs slender, without visible scales; fore femur 0.4 mm long, tibia 0.45 mm long, 1 st tarsomere 1 0.1 mm long; hind femur 0.4 mm long, tibia 0.3 mm long, 1 st tarsomere 1 0.1 mm long; femora and tibiae not swollen; tibial spurs absent; all basal tarsomeres very short.

Abdomen (female) elongate, 0.4 mm long, 0.3 mm wide in mid part; ovipositor elongate. Male unknown.

Type locality and horizon. Earliest Eocene, in amber, ca. -53 My, Sparnacian, level MP7 of the mammal fauna of Dormaal, farm Le Quesnoy, Chevrière, region of Creil, Oise department (northern France) .

Remarks. After Wood & Borkent (1986, 1989), Rhipidoxylomyia rasnitsyni sp. nov. falls in the Cecidomyiidae rather than in Sciaridae , for the presence of the same characters as above. After the phylogenetic hypothesis of Jaschhof & Jaschhof (2013: fig. 21), R. rasnitsyni sp. nov. falls in the ( Winnertziinae + ( Porricondylinae + Cecidomyiinae)) because of the following putative synapomorphies: ocelli all absent, first tarsomeres shorter than second, antC and R5 confluent. But Rhipidoxylomyia rasnitsyni sp. nov. has no circumfila, a plesiomorphic state of character absent in the clade ( Porricondylinae + Cecidomyiinae), but present in the Winnertziinae .After Sikora et al. (2019), theWinnertziinae (viz. Diallactini, Heteropezini , Winnertziiini) would be paraphyletic, with the Heteropezini and Winnertziini monophyletic whereas Diallactiini was not.

After Tasta-Duque (2001), affinities with the Diallactiini are excluded because Rhipidoxylomyia rasnitsyni sp. nov. has no M1+2. Following the keys to Nearctic and European genera proposed by Gagné (1981, 1994) and Skuhravá (1997), the Heteropezini are excluded because of the presence of 12 flagellomeres. Following Jaschhof & Jaschhof (2013: 48, fig. 21), some Heteropezini have either five tarsomeres with the second tarsomere being two to four times longer than the basitarsus, as in Rhipidoxylomyia rasnitsyni sp. nov., while others have less than five tarsomeres, unlike Rhipidoxylomyia rasnitsyni sp. nov. Also Rhipidoxylomyia rasnitsyni sp. nov. has an ovipositor strongly prolonged, a synapomorphy of the Winnertziini . Rhipidoxylomyia rasnitsyni sp. nov. also shares with the Winnertziini 12 flagellomeres. Thus, I attribute it to this tribe rather than to the others. Rhipidoxylomyia rasnitsyni sp. nov. also falls in the Winnertziini after the key of Panelius (1965) for the following characters: M1+2 absent, female antenna without circumfila, wing with breadth no less than 0.45 of length, M4 present.

The key to genera of Winnertziini of Mamaev & Zaitzev (1998) is based on male structures and on tarsal characters that are unknown in Rhipidoxylomyia rasnitsyni sp. nov. Thus, it cannot be used to determine the generic affinities of the new fossil.

After Spungis (1992: 7), Jiang & Bu (2004), and Jaschhof & Jaschhof (2013) , four translucent sensoria each with two divergent forks is a diagnostic character of the female Rhipidoxylomyia , present in Rhipidoxylomyia rasnitsyni sp. nov.

Rhipidoxylomyia rasnitsyni sp. nov. differs from the Recent genera Sylvenomyia Mamaev & Zaitzev, 1998 (considered as a junior synonym of Rhipidoxylomyia in Gagné & Jaschhof, 2014 , but reinstated by Gagné & Jaschhof, 2021 ), Cryptoxylomyia Mamaev, 1995 (considered as a junior synonym of Rhipidoxylomyia in Gagné & Jaschhof, 2014 and 2021, but reinstated by Plakidas, 2019), Parwinnertzia Felt, 1919 , and the fossil genera Electroxylomyia Nel & Prokop, 2006 and Cretowinnertzia Gagné, 1977 in the presence of a distinct M4 (Gagné, 1977; Mamaev & Zaitzev, 1998; Nel & Prokop, 2006; Jaschhof & Jaschhof, 2013: 64 ).

Winnertzia Rondani, 1861 (junior synonym Shevchenkia Fedotova & Sidorenko, 2005 ), Vasiliola Fedotova 2004 , Clinorhytis Kieffer, 1896 , and Kronomyia Felt, 1911 differ from Rhipidoxylomyia rasnitsyni sp. nov. in the basal part of M4 present, even if it can be faint in these genera ( Kieffer, 1913; Mamaev, 1963; Panelius, 1965; Parnell, 1971; Fedotova & Perkovsky, 2005; Fedotova & Sidorenko, 2005; Perkovsky & Fedotova, 2008; Jaschhof & Jaschhof, 2009 ).

The wing venation of Rhipidoxylomyia rasnitsyni sp. nov. is similar to those of Rhipidoxylomyia and Ekmanomyia Jaschhof in Jaschhof & Jaschhof, 2013 , with basal part of M4 strongly reduced ( Jaschhof & Jaschhof, 2013 : fig. 28). These two genera differ in the structure of the antennal translucent sensilla and of the male tegmen, two characters impossible to see in our fossil.

Rhipidoxylomyia rasnitsyni sp. nov. has 12 flagellomeres instead of 10 to 11in recent Rhipidoxylomyia ( Mamaev, 1964; Jaschhof & Jaschhof, 2013: 71 ; Jiang & Bu, 2004; Plakidas, 2019), while Ekmanomyia has also 12 flagellomeres. Jiang & Bu (2004) proposed a key to the extant species of Rhipidoxylomyia based on male characters, mainly terminalia. Thus, we did not attempt to further compare the new species to the extant ones. The only other fossil species Rhipidoxylomyia vaga Fedotova & Perkovsky, 2008 (Eocene Rovno amber) also has 12 flagellomeres, but it differs from Rhipidoxylomyia rasnitsyni sp. nov. in the necks of the flagellomeres being half as long as the nodes. Rhipidoxylomyia . vaga would need to be revised. Nothing is known on the sensoria of Rhipidoxylomyia vaga . In Ekmanomyia , the neck of fourth flagellomere is nearly as long as node, unlike in Rhipidoxylomyia rasnitsyni sp. nov. The male of Ekmanomyia have linear and very long translucent sensilla, unlike Rhipidoxylomyia rasnitsyni sp. nov., but the females seem to remain unknown in Ekmanomyia . For these reasons, I tentatively put this fossil in Rhipidoxylomyia .

Figures

FIGURE 3. Rhipidoxylomyia rasnitsyni sp. nov., holotype PA 12413 ½, female, habitus. A, Microphotograph. B, Drawing. Scale bar = 1 mm.

FIGURE 4. Rhipidoxylomyia rasnitsyni sp. nov., holotype PA 12413 1/2, female. A, Microphotograph of antenna. B, Drawing of detail of flagellomere. Scale bar = 0.05 mm.

FIGURE 5. Rhipidoxylomyia rasnitsyni sp. nov., holotype PA 12413 ½, female. A, Microphotograph of wing. B, Drawing of wing. Scale bar = 0.5 mm.