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Late Cretaceous Land Plants
Information about terrestrial plants from Australia from the Late
Cretaceous has been gathered from impressions, stems, cones
(reproductive structures), mineralised wood, cuticles, spores and
pollen. According to the authors3
there is evidence in the fossil record from the Late Cretaceous that
changes in rainforest and woodland communities, though a large part of
the record is geographically and stratigraphically patchy.
Species of forest and woodland communities have been found in the
macrofloras of the Winton Formation from the uppermost-Cenomanian.
Conifers are mainly the dominant type of vegetation that includes
several araucarians (Araucaria),
Elatocladus (a podocarp), Ginkgo and sequoias
(Taxodiaceae) such as Athrotaxus and Australosequoia
wintonensis. The authors3
have suggested probable understorey plants that include pentoxylaceans (Taeniopteris)
and ferns such as Sphenopteris and
Microphyllopteris, and along the edges of lakes
and swamps, horsetails and quillworts. There have also been a number of
angiosperms recorded. Leaf impressions have allowed the identification
of magnolias, mineralised flowers Lovella wintonensis,
and fruiting structures. In localities in the Gippsland Basin and the
Otway Basin, southern Victoria, similar macrofloras, with spores and
pollen, from the Cenomanian have been found. Regional differences
are apparent in the fossil record such as lower angiosperm diversity and
a flora that is adapted to wet zones that is generally more pervasive.
Apart from some cuticle and leaf fragments found in drill cores
from the Otway Basin,
microfossils are almost the only evidence of plants from the Late
Cretaceous. What evidence there is indicates that around the
Cenomanian-Turonian boundary there were profound changes in the
vegetation, including the introduction of modern elements such as
Ilex (holly) and proteas such as
Banksia. The authors3
suggest the migration routes taken by the new arrivals in Australia were
probably via southern high-latitude regions, the new taxa becoming
established elements of the flora by the Santonian. Proteacean lineages
of the present such as Macadamia had begun to
differentiate, as well as other austral
angiosperms that were
characteristic of the Australian vegetation such as Winteraceae and
Nothofagus
(southern beech) by the Campanian-Masstrichtian. The authors3
suggest that somewhere in South America-Antarctic Peninsula appears to
be the place of origin of Nothofagus. At the
present it is widely distributed throughout many continental fragments
of Gondwana, such as Australia, New Guinea, New Zealand, New Caledonia
and South America.
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