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Natural history of New Zealand
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Natural history of New Zealand
The natural history of New Zealand began when the landmass Zealandia – today an almost entirely submerged mass of continental crust with New Zealand and a few other islands peaking above sea level – broke away from the supercontinent Gondwana in the Cretaceous period. Before this time, Zealandia shared its past with Australia and Antarctica. Since this separation, the New Zealand landscape has evolved in physical isolation, although much of its current biota has more recent connections with species on other landmasses. The exclusively natural history of the country ended in about 1300 AD, when humans first settled there, and the country's environmental history began. The period from 1300 AD to today coincides with the extinction of many of New Zealand's unique species that had evolved there.
The break-up of Gondwana left the resulting continents, including Zealandia, with a shared ecology. Zealandia began to move away from the part of Gondwana which would become Australia and Antarctica approximately 85 million years ago (Ma). By about 70 Ma, the break up was complete. Zealandia has been moving northwards ever since, changing both in relief and climate. Most of the present biota of New Zealand has post-Gondwanan connections to species on other landmasses, but does include a few descendants of Gondwanan lineages, such as the Saint Bathans mammal. Overall, trans-oceanic dispersal has played a clear role in the formation of New Zealand's biota. Several elements of the Gondwana biota are present in New Zealand today: predominantly plants, such as the podocarps and the southern beeches, but also distinctive insects, birds, frogs and the tuatara.
In the Duntroonian stage of the Oligocene, the land area of Zealandia was at a minimum. It has been suggested that water covered all of it, but the consensus is that low-lying islands remained, perhaps a quarter of the modern land area of New Zealand.
In the late Cretaceous, Gondwana was a fraction of its original size, however, the landmasses that would become Australia, Antarctica and Zealandia were still attached. Most of the modern 'Gondwanan fauna' had its origin in the Cretaceous. During this time Zealandia was temperate and almost flat, with no alpine environments.
Fossils found at Lightning Ridge, New South Wales, suggest that 110 million years ago (Ma), Australia supported a number of different monotremes, but did not support any marsupials. Marsupials appear to have evolved during the Cretaceous in the contemporary northern hemisphere, to judge from a 100-million-year-old marsupial fossil, Kokopellia, found in the badlands of Utah. Marsupials would then have spread to South America and Gondwana. The first evidence of mammals (both marsupials and placental) in Australia comes from the Tertiary, and was found at a 55-million-year-old fossil site at Murgon, in southern Queensland. As Zealandia had rifted away at this time it explains the lack of ground-dwelling marsupials and placental mammals in New Zealand's fossil record.
Dinosaurs continued to prosper but, as the angiosperms diversified, conifers, bennettitaleans and pentoxylaleans disappeared from Gondwana c. 115 Ma together with the specialised herbivorous ornithischians, whilst generalist browsers, such as several families of sauropodomorph Saurischia, prevailed. The Cretaceous–Paleogene extinction event killed off all dinosaurs except birds, but plant evolution in Gondwana was hardly affected. Gondwanatheria is an extinct group of non-therian mammals with a Gondwanan distribution (South America, Africa, Madagascar, India, and Antarctica) during the Late Cretaceous and Palaeogene. Xenarthra and Afrotheria, two placental clades, are of Gondwanan origin and probably began to evolve separately c. 105 Ma when Africa and South America separated.
Angiosperms evolved in northern Gondwana/southern Laurasia during the Early Cretaceous and radiated worldwide. The southern beeches, Nothofagus, are prominent members of this early angiosperm flora. The Late Cretaceous pollen record shows that some types of flora evolved across Gondwana, while others originated in Antarctica and spread to Australia. Fossils of Nothofagus have also recently been found in Antarctica. The laurel forests of Australia, New Caledonia, and New Zealand have a number of species related to those of the laurissilva of Valdivia, through the connection of the Antarctic flora. These include gymnosperms and the deciduous species of Nothofagus, as well as the New Zealand laurel, Corynocarpus laevigatus, and Laurelia novae-zelandiae. At this time Zealandia was mostly covered in forests of podocarps, araucarian pines, and ferns.
The Australia-New Zealand continental part of Gondwana split from Antarctica in the late Cretaceous (95–90 Ma). This was followed by Zealandia separating from Australia (c.85 Ma). The split started from the Southern end and eventually formed the Tasman Sea. By about 70 Ma, the continental crust of Zealandia separated from Australia and Antarctica. However, it is not known when the division of land above sea level occurred, and for some time only shallow seas would have separated Zealandia and Australia in the north. Dinosaurs continued to live in New Zealand and had about 10–20 million years to evolve unique species after they separated from Gondwana.
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Natural history of New Zealand
The natural history of New Zealand began when the landmass Zealandia – today an almost entirely submerged mass of continental crust with New Zealand and a few other islands peaking above sea level – broke away from the supercontinent Gondwana in the Cretaceous period. Before this time, Zealandia shared its past with Australia and Antarctica. Since this separation, the New Zealand landscape has evolved in physical isolation, although much of its current biota has more recent connections with species on other landmasses. The exclusively natural history of the country ended in about 1300 AD, when humans first settled there, and the country's environmental history began. The period from 1300 AD to today coincides with the extinction of many of New Zealand's unique species that had evolved there.
The break-up of Gondwana left the resulting continents, including Zealandia, with a shared ecology. Zealandia began to move away from the part of Gondwana which would become Australia and Antarctica approximately 85 million years ago (Ma). By about 70 Ma, the break up was complete. Zealandia has been moving northwards ever since, changing both in relief and climate. Most of the present biota of New Zealand has post-Gondwanan connections to species on other landmasses, but does include a few descendants of Gondwanan lineages, such as the Saint Bathans mammal. Overall, trans-oceanic dispersal has played a clear role in the formation of New Zealand's biota. Several elements of the Gondwana biota are present in New Zealand today: predominantly plants, such as the podocarps and the southern beeches, but also distinctive insects, birds, frogs and the tuatara.
In the Duntroonian stage of the Oligocene, the land area of Zealandia was at a minimum. It has been suggested that water covered all of it, but the consensus is that low-lying islands remained, perhaps a quarter of the modern land area of New Zealand.
In the late Cretaceous, Gondwana was a fraction of its original size, however, the landmasses that would become Australia, Antarctica and Zealandia were still attached. Most of the modern 'Gondwanan fauna' had its origin in the Cretaceous. During this time Zealandia was temperate and almost flat, with no alpine environments.
Fossils found at Lightning Ridge, New South Wales, suggest that 110 million years ago (Ma), Australia supported a number of different monotremes, but did not support any marsupials. Marsupials appear to have evolved during the Cretaceous in the contemporary northern hemisphere, to judge from a 100-million-year-old marsupial fossil, Kokopellia, found in the badlands of Utah. Marsupials would then have spread to South America and Gondwana. The first evidence of mammals (both marsupials and placental) in Australia comes from the Tertiary, and was found at a 55-million-year-old fossil site at Murgon, in southern Queensland. As Zealandia had rifted away at this time it explains the lack of ground-dwelling marsupials and placental mammals in New Zealand's fossil record.
Dinosaurs continued to prosper but, as the angiosperms diversified, conifers, bennettitaleans and pentoxylaleans disappeared from Gondwana c. 115 Ma together with the specialised herbivorous ornithischians, whilst generalist browsers, such as several families of sauropodomorph Saurischia, prevailed. The Cretaceous–Paleogene extinction event killed off all dinosaurs except birds, but plant evolution in Gondwana was hardly affected. Gondwanatheria is an extinct group of non-therian mammals with a Gondwanan distribution (South America, Africa, Madagascar, India, and Antarctica) during the Late Cretaceous and Palaeogene. Xenarthra and Afrotheria, two placental clades, are of Gondwanan origin and probably began to evolve separately c. 105 Ma when Africa and South America separated.
Angiosperms evolved in northern Gondwana/southern Laurasia during the Early Cretaceous and radiated worldwide. The southern beeches, Nothofagus, are prominent members of this early angiosperm flora. The Late Cretaceous pollen record shows that some types of flora evolved across Gondwana, while others originated in Antarctica and spread to Australia. Fossils of Nothofagus have also recently been found in Antarctica. The laurel forests of Australia, New Caledonia, and New Zealand have a number of species related to those of the laurissilva of Valdivia, through the connection of the Antarctic flora. These include gymnosperms and the deciduous species of Nothofagus, as well as the New Zealand laurel, Corynocarpus laevigatus, and Laurelia novae-zelandiae. At this time Zealandia was mostly covered in forests of podocarps, araucarian pines, and ferns.
The Australia-New Zealand continental part of Gondwana split from Antarctica in the late Cretaceous (95–90 Ma). This was followed by Zealandia separating from Australia (c.85 Ma). The split started from the Southern end and eventually formed the Tasman Sea. By about 70 Ma, the continental crust of Zealandia separated from Australia and Antarctica. However, it is not known when the division of land above sea level occurred, and for some time only shallow seas would have separated Zealandia and Australia in the north. Dinosaurs continued to live in New Zealand and had about 10–20 million years to evolve unique species after they separated from Gondwana.