A CENOZOIC FOSSIL INSECT ASSEMBLAGE FROM ANTARCTICA

The arthropod fauna of Antarctica today consists of species of mites and springtails. The only insects to occur anywhere on the continent are from the northern tip of the Antarctic Peninsula and consist of only 2 species of midges (Diptera: Chironomidae). The fossil record for Antarctic insects is also very poor and mostly for the Mesozoic. Several fragments of insects have been discovered from indurated siltstones in the Meyer Desert Formation (Sirius Group), from outcrops in the Transantarctic Mountains on the Beardmore Glacier (lat. 85° S), about 500 km from the South Pole. The fossils include the skeletal parts of 3 species of Coleoptera (beetles) and a species of Diptera (fly). Most of the Coleoptera fragments are of Curculionidae (weevils). They include a head capsule, fragments of pronota and leg parts. The head, based on the rostrum and the mandible, is assigned to the Listroderina in the Listroderes Group, but is probably not closely related to any of the living species which inhabit southern South America. Both of the pronota are also listroderines, one of them also in the Listroderes group but the other in the Falklandius/Telurus group. In southern South America, listroderines typically inhabit open vegetation on the margins of Nothofagus (southern beech) forest. In the fossil assemblage, the weevils are associated with the pollen, wood and leaves of an extinct deciduous species described as N. beardmorensis, The only other beetle fossil is the fragment of the base of an elytron, possibly representing the family Helodidae, the species of which inhabit emergent vegetation. The Diptera are represented by the posterior segment of the puparium of a cyclorrhaphan (higher fly). The spiracles are evident on the specimen but spiracular plates which would enable identification to the family level are absent. The stratigraphy and paleontology of the deposits indicates that insects, together with plants and freshwater molluscs and a fish had dispersed up the Beardmore Fiord during an interglacial warm interval. The age of the deposits is controversial but based on derived marine diatoms could be as young as Pliocene. The low pollen diversity indicates that the assemblage could be of Pliocene age based on comparison with a Ross Sea assemblage. The mean summer temperature indicated by the fossil insects and other fossils was about 5° C .