A keystone in a changing world - Antarctica: Global Science from a Frozen Continent - page 63

Figure 2.28 Artistic recreation of what a Cretaceous forest on Antarctica might have looked

like. (Credit: Robert Nicholls)

global climates. A mean annual temperature of about 19ºC prevailed with warm
frost-free winters. Subtropical flora grew in warm climates on the volcanic arc

surviving the environmental catastrophe that saw the extinction of the dinosaurs
65 million years ago.
When the (flowering plants) evolved, the continuity of the

landmasses enabled them to spread globally. As the continents moved apart and
linkages were severed, descendants of the

first angiosperms (

first angiosperms could spread only where
migration routes remained open. Distinct modern floras of the various continents

are products of evolution in isolation since the separation of land masses. Sixty
million years ago, Australia oor

spreading in the Tasman Sea isolated New Zealand. Evolution in Australia, New
Zealand and South America was from the animals and plants of Gondwana, and
the individual modern

' s last Gondwana links were severed and sea

flora and fauna of all three clearly show these common roots.
Ghosts of the Gondwana flora are common in present New Zealand vegetation,

e.g. totora, kauri and Nothofagus (beech) trees.
Younger fossil plants (55 40 my old) hold vital clues to a major change in climate

at that time. The warm loving types disappeared, replaced instead by trees that were
tolerant of cool climates. The southern beech, Nothofagus , became most common in

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