What interesting specimen was discovered at Seymour Island, Antarctica in 1982?

A fossil marsupial of the extinct family Polydolopidae was found on Seymour Island in 1982. This was the first evidence of land mammals having lived in Antarctica. Further fossils have subsequently been found, including members of the marsupial orders Didelphimorphia (opossum) and Microbiotheria, as well as ungulates and a member of the enigmatic extinct order Gondwanatheria, possibly Sudamerica ameghinoi.

The rocks making up Seymour Island date mainly from the Late Cretaceous to the Eocene. Successively younger rock formations found on the island are the López de Bertodano Formation (Cretaceous to early Paleocene) Sobral Formation and Cross Valley Formation (Paleocene) and La Meseta Formation (Eocene). Seymour Island has been referred to as the Rosetta Stone of Antarctic palaeontology, due to the unparalleled insight it provides into the geological and palaeontological history of the continent.