East Gondwana

This prevented permanent ice sheets from developing and fostered polar forests, which were largely dominated by conifers, cycads, and ferns, and relied on a temperate climate and heavy rainfall.

This area has yielded an array of both macro- and micro- plant and mollusk fossils representative of the Early Cretaceous, as well as the Middle to Late Jurassic.

[8] The Cretaceous is characterized by warm global temperatures caused by the high amounts of carbon dioxide and possibly methane greenhouse gases in the atmosphere.

The vegetation was largely made up of conifers, cycads, and other gymnosperms, as well as ferns; on the forest floor grew lycopods, bryophytes, fungi, and algae.

[13][14] In the Early Cretaceous, East Gondwana (Australia, Antarctica and Zealandia) had started to split away from South America, and India and Madagascar also began to separate at around the same time.

The discovery of several mature evergreen and deciduous trees indicate a warm-to-cool temperature with moderate seasons lacking widespread freezing, at least between the latitudes 70 and 85°S.

[17] Much of what is known of the plant life of East Gondwana during the Cretaceous consists of pollen remains and leaf compressions from the northern Antarctic Peninsula.

[23][24] The total polar ice coverage during the Mesozoic may have been a third of the size as it is in modern times, though cold snaps of subfreezing temperatures possibly occurred throughout the Early Cretaceous.

[27] Evidence of flowering plants dating to around 80 Ma in the Late Cretaceous suggests the existence of temperate forests–similar to those in present-day Australia, New Zealand, and southern South America.

[27] The Late Cretaceous (Campanian) Zamek and Half Three Point Formations of King George Island were located at 60°S and display a rich assemblage of fossil flora, such as Podocarpus; Araucaria; the leptosporangiate ferns Cladophlebis and Clavifera; and a variety of Magnoliopsida flowering plants, Dicotylophyllum, Myrciophyllum santacruzensis, Nothofagus, Sterculiaephyllum australis, Monimiophyllum, and so forth.

[30][31][32] The Sobral Formation of Seymour Island spanning the Cretaceous–Paleogene boundary at a paleolatitude of 63°S provided a new genus of fossil flower in the family Cunoniaceae, Eucryphiaceoxylon eucryphioides.

[33] Much as in Australia today, East Gondwana played host to many endemic animals, which included many relict species of families that had gone extinct in the rest of the Cretaceous world.

It is possible the polar regions of the Late Cretaceous had been inhabited by groups of plants and animals whose ancestry can be traced back to the Ordovician.

[16][34] The gradual isolation of Antarctica in the Late Cretaceous created a distinct group of aquatic creatures called the Weddellian Province.

[34] The South Polar iguanodontian Muttaburrasaurus is most closely related to European rhabdodontids, which were the dominant group in Europe during the Late Cretaceous.

However, the lack of an abrupt extinction horizon in Antarctic or Australian sediments for plant and bivalve fossils during this time period indicates a less powerful impact in the South Polar region.

[16] Given that the dinosaurs and other fauna of the polar regions of the Cretaceous were well adapted for living in long periods of dark and cold weather, it has been postulated that this community might have survived the event.

These neosuchians, at an adult size of no more than 2.5 metres (8.2 ft) in length, likely led to the extinction of the temnospondyls in tandem with more-developed ray-finned fish which perhaps targeted their larvae.

[52] Plesiosaurs inhabited freshwater river and estuary systems, given the locations of their remains, probably colonizing Australia in the Early to Middle Jurassic.

The discovery of several juvenile plesiosaur remains suggest they used the nutrient-rich waters of the coast as sheltered calving grounds, the cold deterring predators such as sharks.

[53] The coastal area may have experienced winter freezing, and these reptiles, in response, may have migrated north during the winter, had a more active metabolism than tropical reptiles, have hibernated in freshwater areas much like the modern day American alligator (Alligator mississippiensis), or have been endothermic similar to modern day leatherback sea turtles (Dermochelys coriacea).

[53] Several Late Cretaceous oceanic plesiosaurs and mosasaurs have been discovered in New Zealand and Antarctica, with some, such as Mauisaurus, being endemic, while others, such as Prognathodon, having a cosmopolitan distribution.

[56] Two clades of pterosaurs are represented in Early Cretaceous Australia, Pteranodontoidea and Ctenochasmatoidea, remains mainly deriving from the Toolebuc Formation and areas of Queensland and New South Wales.

[16][34] Of the Late Cretaceous pterosaurs, only the remains belonging to the family Azhdarchidae–found in the Carnarvon and Perth basins in Western Australia–were assigned to a taxon.