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a small herbivorous hypsilophodontid, and hadrosaurus, the larger herbivorous
duck-billed dinosaur. The diverse and interesting fossil history of Antarctica would
not be complete without mentioning the long invertebrate fossil record known from
the Lower Cambrian (about 500million years ago ) onwards. For the most part they
are marine in origin with rare occurrences of freshwater and terrestrial species,
archaeocyathids, trilobites, molluscs, brachiopods, crinoids, echinoderms, corals,
serpulids, crustaceans and bryozoans.
The fragmentary fossil record from Antarctica indicates that a surprisingly
wide variety of organisms lived on or around Antarctica. The southern continent
has been colonised by a succession of plants and animals that shows signs of
being as complex as those on any other continent. Vast habitat areas for occupation
by both terrestrial and marine organisms, coupled with equitable climates for very
long periods of time, have contributed towards this proliferation of life. Antarctica
seems to have been a particularly important dispersal route and undoubtedly served
as a major corridor for
floral and faunal interchange between the high and low
southern latitudes. A number of plant and animal groups seem to have both
originated in, and then radiated from the high southern latitudes. Even after the
marked climate cooling and loss of habitats through the Cenozoic (last 65million
years) there still appears to have been adaptive radiations especially in the marine
realm. It is possible that temperate, cool temperate and even cold temperate regions
of the world have been very effective in the process of species diversi
cation.
Continued investigations of the fossil record may provide valuable insights into
the role of the polar regions in determining the contribution of high latitude regions
to the global species pool.
A land of
re
The relative peace and tranquillity of Gondwana was disrupted approximately
183million years ago by an extensive but relatively short-lived period of volcanic
activity that heralded the break-up and disintegration of the supercontinent. The
intensive volcanism, which lasted for less than a million years, stretched from
what was to become Southern Africa into Antarctica, along the length of the
Transantarctic Mountains, and on into Tasmania and New Zealand, a distance
over 3000 km. Although much of the volcanic debris that was ejected from
numerous volcanoes has been eroded, we are left with an impressive network of
subvolcanic conduits, mostly horizontal (sills) but some vertical (dykes) layers that
record the passage of hot magma from its source within the Earth
s mantle. Today, if
you stand in the Transantarctic Mountains, you cannot but be impressed by the
lateral continuity of these sills that stretch for literally hundreds of kilometres along
the steep escarpment. In the Theron Mountains, more than 20 such sills form over
'
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