First hanging fly fossil from South America

PETRULEVICIUS J. F.

Moscú

Conferencia; First Paleoentomological Conference; 1998

Bittacids are rare in the fossil record. Three genera are mentioned, restricted to the Kazakhastan Jurassic (Probittacus), USA Eocene (Palaeobittacus), Baltic and England Oligocene, and USA Eocene (Bittacus). The specimen was collected from the late Paleocene Maíz Gordo Formation, composed by green mudstones and shales, near La Mendieta (24° 21´ S; 64° 59´ W), Northwest Argentina. The remain is a hindwing?, three-dimensionally preserved, original length estimated at 13·1 mm. Wing elongate, slender in basal third, broadened distally, with few crossveins. ScP extending beyond midwing. R curved posteriorly in basal third. Crossveins from posteriorly curved RA3+4 to RP1+2 and to RP1. MA diverging from RP. MA, MP1+2, MP3+4 and CuA linked by three crossveins. MP1, 4 distally curved. MP2, 3 nearly straight. MP4 partially? fused with CuA. Presence of CuA? and three additional bad preserved branches?. CuA3+4? reach the wing margin at 45°. Incision on wing margin at end of CuP, little less marked than in Probittacus. Only AA3? fused for a short distance with CuP, AA4? continues not fused (new genus Autapomorphy). CuP reaching the margin at 3/5 of the wing length, AA3+4 at 2/5. Two aa3+4-ap1+2crossveins. This bittacid wing seems to represent a new genus and species because it can not be related to any genera of the family. The monophyletic group Tytthobittacus + Edriobittacus (+ Austrobittacus?) (Australia) has to be excluded because of its long fusion (less in Austrobittacus) of CuP with AA3+4. In Thyridates + Neobittacus (South America), RP1+2 base forks at 90° from RP. Kalobittacus + Nannobittacus + Issikiella + Pazius (Central and South America) are to be excluded in view of the same apomorphy of Edriobittacus (convergence). In Anabittacus (South America), M4+CuA1+2 arises at the first fork of M, and crossveins between RA3+4 and RP are absent. The genus Bittacus (Europe, Asia and America) differs by having more crossveins, and R and M veins more zigzagged. Hylobittacus (North America) has to be excluded because it has one crossvein between RA3+4 and RP1+2, and a different shape of RA3+4. Harpobittacus (Australia) has the basal part of RP3 (up to pterostigma) parallel to the anterior wing margin, and the apical part of RP and M veins postero-distally curved. The fossil genus Palaeobittacus has a more proximal fork of RP and a crossvein between RP and MP. Probittacus has two scp-ra crossveins, R and M veins strongly zigzagged, and one crossvein between RA3+4 and RP1+2. The fork of MP4 and CuA is a plesiomorphic character shared by Probittacus and Palaeobittacus and probably by the new bittacid. Extant hanging flies have characteristic behaviour. Adults live from spring to autumn and occur in leafy vegetation (herbaceous or low shrubs) and less often in tall grass. They fly along short distances and suspend in vegetation to prey on soft bodied insects with their fore legs. The family is widespread and has a temperate-tropical distribution. The new bittacid was probably a major predator on little arthropods like spiders and Fulgoroidea; both well represented in the late Paleocene entomofauna. Furthermore, the study of this taxa and the whole entomofauna will bring new clues in the understanding of the environmental conditions during the deposition of the bearing strata.