Fossil weevils (Coleoptera: Curculionidae) from latitude 85°S Antarctica

Two species of fossil listroderine weevils (Coleoptera: Curculionidae: Rhytirhinini: Listroderina) are reported from the Meyer Desert Formation at a locality on the Beardmore Glacier in the Transantarctic Mountains about 500 km from the South Pole. Associated fossils include wood, leaves and pollen of Nothofagus, stems and leaves of several species of mosses, achenes of Ranunculus, shells of freshwater molluscs and a fish tooth. The age of the fossiliferous strata is contentious but probably within the range of Pliocene to mid-Miocene. The fossils represent organisms that colonised the margins of a glacier at the head of a fjord during an interglaciation. The autecology of the listroderine species indicates that temperatures during summer months averaged 5°C. The mean annual temperature, with winter temperatures constrained by 6 months of darkness, is estimated to have been about −8°C compared to the −26°C estimated for sea level at latitude 85°S today. The closest evolutionary link of the fossil listroderines is with South American rather than Australian or New Zealand taxa. Divergence of the taxa, at least at the level of tribe, had most probably occurred on Gondwana before the continent broke apart. The fossil species are considered to be the descendants of Antarctic lineages which evolved on the continent in the Late Cretaceous or Palaeogene and survived until the Neogene. Extinction of the listroderines and most other Antarctic terrestrial biota occurred with the growth of the polar ice sheets and the change to the polar desert climate.