Corbiculate bees from the Middle Eocene of Río Pichileufú, Patagonia, Argentina

Middle Eocene bees are quite common in the Northern Hemisphere, and include the corbiculates of the Baltic amber, Messel and Eckfeld Maars (Germany) and the Parachute Creek Member of the Green River Formation (USA). As a result of persistent research on Patagonian localities, principally from Eocene ages, a couple of bees were recovered from a Middle Eocene (48 Ma) locality of Río Pichileufú, Río Negro province, Argentina. One of the bees has a conspicuous corbicula in the metatibia and 6–7 comb rows on the inner surface of a wide and elongated metabasitarsus. In addition, pollen clusters of monoporate (probable Poaceae) and tricolpate pollen grains are preserved on the abdomen. The previously known localities with fossil corbiculate bees in North America and Northern Europe share with Río Pichileufú, an early Lutetian age and a high palaeolatitude. The present discovery of eusocial bees in the Southern Hemisphere, together with the known distributions in the Northern Hemisphere, suggest a bihemispheric distribution in high latitudes for the clade Corbiculata during the middle Eocene.