The Early Miocene Cape Melville Formation fossil assemblage and the evolution of modern Antarctic marine communities
The fossil community from the Early Miocene Cape Melville Formation (King George Island, Antarctica) does not show the archaic retrograde nature of modern Antarctic marine communities, despite evidence, such as the presence of dropstones, diamictites and striated rocks, that it was deposited in a glacial environment. Unlike modern Antarctic settings, and the upper units of the Eocene La Meseta Formation on Seymour Island, Antarctica, which are 10 million years older, the Cape Melville Formation community is not dominated by sessile suspension feeding ophiuroids, crinoids or brachiopods. Instead, it is dominated by infaunal bivalves, with a significant component of decapods, similar to present day South American settings. It is possible that the archaic retrograde structure of the modern community did not fully evolve until relatively recently, maybe due to factors such as further cooling and isolation of the continent leading to glaciations, which resulted in a loss of shallow shelf habitats.