Prosphyracephala kerneggeri Kotrba, 2009

Perkovsky, E. E., Mostovski, M. B. & Henderickx, H., 2015, New Records Of The Dipteran Genera Triphleba (Phoridae) And Prosphyracephala (Diopsidae) In Rovno And Baltic Ambers, Vestnik Zoologii 49 (3), pp. 245-250 : 248-249

Prosphyracephala kerneggeri Kotrba, 2009 ( fig. 1 , f; g, 2)

M a t e r i a l. HH Diopsidae P. kerneggeri ( fig. 1 , f), sex unknown, Baltic amber, Late Eocene. The specimen was obtained from a Lithuanian dealer and had been probably found in Yantarnyi.

R e m a r k s. Previously, P. kerneggeri was known only from the holotype with missing wing parts. A second, recently found complete specimen of P. kerneggeri ( fig. 1 , g), enables a wing venation drawing of this species to be completed ( fig. 2).

Representatives of the genus Prosphyracephala are rare in fossil resins; there are no diopsids in representative collections of the Baltic Amber (The amber.., 2001; Sontag, 2003; Perkovsky et al., 2007), although 24 Prosphyracephala specimens have been recorded so far from the Baltic Amber and four from Bitterfeld ( Schumann, 1994; Kotrba, 2009).

There is no alula seen on the photo of P. rubiensis , the position of the antenna base is indistinguishable from that in other Prosphyracephala ( Lewis, 1971) , and there are no reasons to doubt its assignment to this genus ( Feijen, 1989).

The average temperature of the coldest month at the northernmost range of the modern distribution of the stalk-eyed flies in Europe (Szeged, Hungary) is –2 °C ( Papp et al., 1997). It has been hypothesised that winters were not harsher in the Baltic Amber forest ( Archibald, Farrell, 2003). The average January temperature at the Mormon Creek has been calculated as –0.6 °C (standard deviation 3.6 °C; Lielke et al., 2012); while the mean annual temperature (MAT) in that North American locality has been postulated as 14 ± 2.4 °C, which is higher than in Szeged (9.5 °C).

Worth mentioning is that the vast majority of the Old World Diopsidae are strictly thermophilous. In fact, all of them but the five species of brevicornis group of Sphyracephala Say (three Palearctic and two Nearctic ones) frequent tropic and the warmest subtropic areas. The thermophilous Diopsidae are known in the New World neither in past nor in contemporary fauna. Concerning the two living Nearctic species of brevicornis group, all records of one of them and 97 % of another made north of the January isotherm +5 ºC ( Feijen, 1989).

Eocene Arctic fossil floras indicate that temperate (i.e., upper microthermal to lower mesothermal) conditions predominated across intercontinental connections, with early to middle Eocene floras from Greenland and Axel Heiberg Island (50–40 Myr ago) giving MAT estimates of 12–16 °C ( Archibald et al., 2011), probably too cool to support dispersal

Рис. 2. Крыло Prosphyracephala kerneggeri .

of thermophilous Diopsidae . During larger global hyperthermal events linked to injection of greenhouse gasses into the atmosphere from sedimentary reservoirs, Arctic MAT increased by 5–10 °C to perhaps approximately 23 °C with the coldest month mean temperature greater than 8 °C at approximately 85° N palaeolatitude. Three warming events are suggested, the brief Palaeocene–Eocene Thermal Maximum at the Palaeocene–Eocene boundary (approx. 170 kyr long at about 55.5 Ma); the Eocene Thermal Maximum 2 (about 53.5 Ma); and the longer Early Eocene Climatic Optimum , about 2 Myr long at the latest early Eocene. One of these maxima made possible the giant Formiciinae ants to invade North America ( Archibald et al., 2011) .

The diopsid invasion probably occurred later than the above one, possibly during the Middle or, rather, Late Eocene, with no macrothermal routes preserved, and with only survived those available for Diopsidae with the winter diapause ( Feijen, 1989; Papp et al., 1997). This would limit the diopsid dispersion even to warmer New World subtropics, not to mention the tropics.

Authors’ responsibilities. MBM is responsible for the redescription of Triphleba schulmanae, HH for the wing description of Prosphyracephala kerneggeri and for identification of the Rovno diopsid fossil, and EEP for the remaining text.

The authors are very grateful to Brian Brown, Valery Korneyev and Marion Kotrba for their help, to Alexandr Rasnitsyn and Vitaly Nazarenko for photographs, to Ruud van der Weele (Kulemborg) and Neal Evenhuis (Honolulu) for providing important publications. MBM’s research on the Phoridae at the Tel Aviv University is supported by HaMerkaz LeKlita BeMada (Misrad HaKlita, Israel) and by Sidney Kaushansky and John Swidler (RSM Richter, Montreal, Canada).

Figures

Fig. 1. Triphleba schulmanae: a — lateral view, b — dorsal view, c — anterodorsal view, with exposed bifurcate antennae; Prosphyracephala aff. succini: d — habitus, e — wings; Prosphyracephala kerneggeri: f — ventral, g — dorsal; Prosphyracephala succini: h — habitus.