Antarctica: Geologic history
From the end of the Neoproterozoic era to the Cretaceous, Antarctica was part of the supercontinent Gondwana. Modern Antarctica was formed as Gondwana gradually broke apart beginning around 183 Ma. For a large proportion of the Phanerozoic, Antarctica had a tropical or temperate climate, and it was covered in forests.
During the Cambrian period, Gondwana had a mild climate. West Antarctica was partially in the Northern Hemisphere, and during the time, large amounts of sandstones, limestones, and shales were deposited. East Antarctica was at the equator, where seafloor invertebrates and trilobites flourished in the tropical seas. By the start of the Devonian period (416 Ma), Gondwana was in more southern latitudes, and the climate was cooler, though fossils of land plants are known from then. Sand and silts were laid down in what is now the Ellsworth, Horlick, and Pensacola Mountains.
Antarctica became glaciated during the Late Paleozoic icehouse beginning at the end of the Devonian period (360 Ma), though glaciation would substantially increase during the late Carboniferous. It drifted closer to the South Pole, and the climate cooled, though flora remained. After deglaciation during the latter half of the Early Permian, the land became dominated by glossopterids (an extinct group of seed plants with no close living relatives), most prominently Glossopteris, a tree interpreted as growing in waterlogged soils, which formed extensive coal deposits.
Other plants found in Antarctica during the Permian include Cordaitales, sphenopsids, ferns, and lycophytes. At the end of the Permian, the climate became drier and hotter over much of Gondwana, and the glossopterid forest ecosystems collapsed as part of the Permian–Triassic extinction event. There is no evidence of any tetrapods having lived in Antarctica during the Paleozoic.
The continued warming dried out much of Gondwana. During the Triassic period, Antarctica was dominated by seed ferns (pteridosperms) belonging to the genus Dicroidium, which grew as trees. Other associated Triassic flora included ginkgophytes, cycadophytes, conifers, and sphenopsids. Tetrapods first appeared in Antarctica during the Early Triassic epoch, with the earliest known fossils found in the Fremouw Formation of the Transantarctic Mountains. Synapsids (also known as "mammal-like reptiles") included species such as Lystrosaurus, and were common during the Early Triassic.
The Antarctic Peninsula began to form during the Jurassic period (206 to 146 million years ago). Africa separated from Antarctica in the Jurassic around 160 Ma, followed by the Indian subcontinent in the early Cretaceous (about 125 Ma). Ginkgo trees, conifers, Bennettitales, horsetails, ferns and cycads were plentiful during the time. About 80 million years ago, flowering plants became the most diverse groups of plants on the continent. Across Antarctica, coniferous forests, predominantly composed of podocarps and araucarian conifers, dominated throughout the Cretaceous period (143–66 Ma), though southern beech trees (Nothofagus) became prominent towards the end of the Cretaceous. Ammonites were common in the seas around Antarctica, and dinosaurs were also present, though only a few Antarctic dinosaur genera (Cryolophosaurus and Glacialisaurus, from the Early Jurassic Hanson Formation of the Transantarctic Mountains, and Antarctopelta, Trinisaura, Morrosaurus and Imperobator from Late Cretaceous of the Antarctic Peninsula) have been described. …