Palaeoperissomma Kovalev in Kalugina & Kovalev, 1985

Lukashevich, Elena D. & Blagoderov, Vladimir A., 2020, Review of Mesozoic Perissommatidae (Insecta: Diptera), Zootaxa 4718 (4), pp. 481-496 : 491-493

Palaeoperissomma Kovalev in Kalugina & Kovalev, 1985

( Figures 7A, B , 8 A–D)

Palaeoperissomma: Kalugina & Kovalev 1985: 115 .

Palaeoperissomma Kovalev in Kalugina & Kovalev, 1985 : Lukashevich 2011: 32.

Type species. Palaeoperissomma collessi Kovalev in Kalugina & Kovalev, 1985 (Kubekovo, Siberia, J 2).

Species included. Besides type species,? Palaeoperissomma demetrii Kovalev, 1990 (Turga, Transbaikalia, K 1) and P. ornatum Lukashevich, 2011 (Shar Teg, Mongolia, J 3).

Remarks. Two of three known species were described based on the single isolated wings each ( Kalugina & Kovalev 1985; Lukashevich 2011): P. collessi (holotype PIN, No.1255/261) and P. ornatum (holotype PIN, No.4270/2278). An additional specimen of type species (PIN, No.1255/1341) was collected from the same locality (Kubekovo) in 1989 and studied herein ( Fig. 8A, B ). Some characters of living Perissomma are observed in body structures: V-shaped suture of the tipuloid type; thorax with large metanotum; legs slender, rather elongate, without tibial spurs. Probably three ocelli placed close together in a triangle on the dorsum of the head are present too. As in Perissomma , antenna moniliform, rather short and stout, with 11 segments, segments 2 and 3 enlarged (pedicel and first flagellomere), segment 11 very small, all segments with fine setae only. However, all segments are transverse (shorter than broad).

The holotype of? P. demetrii (PIN, No. 1742/667) was re-studied by us ( Figs 7A, B ; 8C, D ). Kovalev (1990) tentatively suggested that it was a male, but re-examination revealed elongated cerci, therefore the specimen is a female. Visible facets are of similar size. In the original description Kovalev noted that the pattern of antenna (11 segments, enlarged pedicel and tiny last flagellomere) and U-shaped suture on mesonotum ( Fig. 7 A,B ) are similar to living Perissomma , however, the robust habitus differs from one of Perissomma and from habitus of Jurassic P. collessi as now became obvious. Due to poor state of wing preservation Kovalev was hesitant in the generic attribution of this species and these doubts remain (see Discussion).

Figures

FIGURE 7. Mesozoic Perissommatinae (modified originals of V.G. Kovalev). A–B.?Palaeoperissomma demetrii Kovalev, 1990, holotype PIN No. 1742/667 (Turga, K1). A. Total view. B. Antenna. C. Total view of Gurvaniella hosbayari Kovalev, 1986, holotype PIN No. 3149/1789 (Gurvan, K1). Scale bars 1 mm. Figs A, B after Kovalev 1990: fig. 105a, b; Fig C after Kovalev 1986: fig. 97a.

FIGURE 8. Mesozoic Perissommatinae. A, B. Head and total view of Palaeoperissomma collessi Kovalev in Kalugina & Kovalev, 1985, PIN No. 1255/1341 (Kubekovo, J2). C, D. Head and total view of?Palaeoperissomma demetrii Kovalev, 1990, holotype PIN No. 1742/667 (Turga, K1). E, F. Head and total view of Gurvaniella hosbayari Kovalev, 1986, holotype PIN No. 3149/1789 (Gurvan, K1). Scale bars 200 μm (A, C, E), 1 mm (B, D, F). Abbreviations: e, eye; f, vein-like fold; o, ocelli.