Gondwana
From Palaeos.org
Gondwana (also known as Gondwanaland) was an ancient landmass that existed from the paleozoic to the cretaceous.
One of the most enduring features of our planet, Gondwana (or Gondwanaland) was a composite continent, made up of South America, Africa, Madagascar, Antarctica, India, other parts of South Asia, and Australia. At one time it even included Florida and most of Southern Europe.
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Naming and formation
This continent was first named by Edward Suess in the 19th century after the Gondwana district in central India. He suggested that it was made up of South America, Africa, Australia and India. This landmass first appeared some 650 million years ago during the last days of the Cryogenian and became part of the southern hemisphere. During the Carboniferous, Gondwana collided with Laurentia during the Variscan Orogeny and was covered by ice sheets which existed until the Early Permian. Prior to the Variscan Orogeny, Gondwana was separated from Laurentia by the Rheic Ocean. Later, along with Laurasia, it became part of the legendary supercontinent Pangea.
Break up
Some time circa 160-130 million years ago, during the Middle Jurassic or Early Cretaceous, Gondwana itself began to break up. The breakup began when East Gondwana (comprising of Antarctica, Australia and Indo-Madagascar) broke free from the remainder of the continent, which was composed from Africa and South America.
Flora and Fauna
The family Proteaceae is widespread around the southern hemisphere, an example of Gondwanan distribution. Throughout Gondwana's long and venerable history, the animals and plants that inhabited it were often quite different to those found in other continents. Here is a very tiny selection.
Late Silurian-Early Devonian Land Plants
Baragwanathia longifolia, one of the earliest known land plants, is known from the late Silurian or early Devonian of Yea, Victoria, Australia. It is a member of the primitive lycopsid order Drepanophycales. The dating, on the basis of graptolites found associated with Baragwanathia, indicates a Ludlow (late Silurian) age, predating or corresponding in age with Cooksonia, a very much more primitive ancestral vascular plant. If this date is correct it means that the late Silurian Gondwanaland flora was much more advanced than the contemporary northern hemisphere flora.
Late Devonian Fish
During the Late Devonian period there was a rich marine fish fauna, found in association with coral reefs, the fossil remains of which are known from early Frasnian age Gogo locality, north-western Australia. This is characterized by a diversity of prehistoric armoured fish known as placoderms (principally, arthrodires)
(1, Eastmanosteus; 2, Latocamurus; 3. Tubonasus; 4, Incisoscutum; 5. Harrytoombsia; 6, Torosteus). Other placoderm groups are represented by the antiarch (7, Bothriolepis) and ptyctodonts (8, Campbellodus). The lobe-finned fishes are lungfishes (9, Holodipterus; 10, Griphognathus) and osteolepiformes (11, Gogonasus). Small ray-finned fishes (12, Mimia) were also fairly common.
Dinosaurs
While better known dinosaurs like Apatosaurus, Stegosaurus, Triceratops, and Tyrannosaurus inhabited the northern continents, Gondwanaland was home to its own unique fauna. These evolved from a common Pangean ancestor (indeed, during the Triassic and Jurassic there was not much difference between dinosaurs in the north and south), but during the Cretaceous, as Gondwana rifted free of Laurasia, and itself in turn began breaking into the continents that are around today, the dinosaurs that lived there evolved into distinct types very different from the northern forms. Among these were large meat-eaters known as abelisaurs, some of which had normal heads (like Abelisaurus here) and others that developed small horns. Although more "primitive" than the contemporary tyrannosaurs of Asiamerica, the abelisaurs were a very successful and widespread group that persisted throughout Gondwanaland until the end of the Cretaceous.
Cenozoic
Antarctica, which served as a sort of "bridge" between different landmasses since immemorable times, began to drift south and and the ice sheet that covers it today began to form around 15 million years ago. The breakup of this continent allowed South America, New Zealand and Australia to become isolated. Such an isolation allowed these three landmasses to develop their own unique faunas (Thylacosmilus in South America, the platypus in Australia and the tuatara in New Zealand). Furthermore, the eastward movement of Africa caused the Tethys Ocean to close and become replaced by the Indian Ocean. Sometime 3 million years ago, the two Americas became one landmass once again as they did numerous times before. With this new connection, fauna from both continents quickly invaded each other's territories.
