FACT
The existing sequoia
trees found mainly
in the United States
were also thought to
have evolved in the
Mesozoic.
Figure 11.10:
Sequoia trees in
California, USA.
FACT
When the
coelocanth was
initially discovered
by an East London
fisherman in 1938
and identified as
such by Professor
JLB Smith, this
surprised scientists
because they
thought it had
become extinct.
Soon there were
other such
discoveries of the
coelocanth off the
coast of Kwa-Zulu
Natal as well as
Northern
Madagascar.
Coelocanths
represent a link
between fish and
amphibians.
- During the Triassic, Archaeopteryx, a link between reptiles and birds was thought to
evolve. - The earliest birds appeared during the Jurassic period having evolved from a species of
dinosaur called theropods. - Dinosaurs became extinct around 65 million years ago, at the end of the Cretaceous
period. - The dominant land plant species of the time were the seed-producing plants known as
thegymnosperms. These include the cycads and conifers.
South African fossil examples: The mammal-like reptile,Lystrosauruswas by far the most
dominant terrestrial vertebrate during the Early Triassic period. Specimens of the lystrosaurus
were unearthed in the Balfour and Katburg formations in the Karoo. The discovery of
Lystrosaurus in the Coalsack Bluff in the Transantarctic Mountains helped confirm the theory
that the continents of the Earth were once joined, asLystrosaurushad already been found in
the Early Triassic fossil record of Southern Africa, India and China.Figure 11.11:Lystrosaurusskeletal diagram.”Living fossils” in South Africa: Coelocanths were thought to have gone extinct towards the
end of the Cretaceous period but were re-discovered in 1983 off the northern coast of South
Africa in Kwazulu-Natal. The coelocanth is thought to have evolved into its current form over
400 million years ago and is nicknamed a ’living fossil’ because knowledge of the species
was previously based on fossils as it was thought to have gone extinct. Coelocanths and
amphibians share a common ancestor-the lobe-finned fish. Lobe finned fish have fleshy fins
unlike fins in other fish which are joined to the body by a single bone. Pectoral and pelvic
fins have articulations resembling those of tetrapod limbs. These fins evolved into legs in
the earliest tetrapod land vertebrates which were amphibians. Living lobe-finned organisms
include the coelocanths and lungfish.Figure 11.12: Coelocanths, which represent a link between fish and amphibians, were though to
have gone extinct at the end of the cretaceous period.328 11.3. Life’s History