Time of the Titans
some of the dinosaurs that lived 152 million years ago.
dinosaurs were pretty small. Eoraptor was about 1 m long,
its contemporary Herrerasaurus grew no more than 4 m long
and Coelophysis was about 3 m long. And in all cases the
length was mostly tail.
However the plant-eating prosauropod, Plateosaurus, that
appeared at the end of the Triassic period, was a harbinger of
things to come. At up to 9 m long it was the first really big
Prosauropods could walk either on all fours or just on their hind
legs, leaving their hands free, perhaps to grasp branches and
bring them within reach of their mouths. They disappeared at the
end of the Early Jurassic period and their role was taken by the
sauropods which thrived during from the Middle Jurassic to the
Early Cretaceous period.
had huge elephantine bodies coupled with very long necks and
tails. They walked only on all fours. Some such as Diplodocus
could probably have reared up on their hind legs using their
tails as props. |
skeletons show a number of features that support this: it has high
vertebral spines over its hip region showing it had strong muscles
and ligaments there and it has skid-like bones underneath its tail
which would have protected the delicate nerves and blood vessels
there when its tail was resting on the ground.
The Morrison Formation
The dinosaurs featured in this episode were all found in the Morrison
Formation, except Anurognathus. The Morrison Formation was
deposited approximately 155-145 million years ago and covers a large
area of the western US, from Montana to Arizona and Utah to Colorado.
In different areas and through time Morrison environments were diverse
ranging from arid deserts in the southwest through rivers and flood
plains to swamps in the north. Fossil plants indicate a rather wetter
environment than the rock record and this may mean that the climate
Keep on Growing!
In the Early Jurassic the maximum size of both herbiviores and carnivores
increased, and this trend continued throughout the Jurassic culminating
in the staggeringly large sauropods such as Apatosaurus and
Brachiosaurus. Carnivores had also increased in size, although
not by as much and the 12m long Allosaurus was dwarfed by
its sauropod prey. They would have had to pick on the young or weak
or maybe they hunted in packs.
Evidence based on growth rings and bone texture indicates that sauropods
reached their adult size in 10-20 years. Also if, as has been suggested,
sauropods took 70 years to reach maturity, it would be unlikley
that many would survive to reproduce. The data indicating that they
grew quickly also fits that from the bones of theropods and ornithopods,
who were thought to reach maturity quickly.
are two main types of dinosaurs, named from the configuration of their
pelvic bones: bird-hipped and lizard-hipped. Sauropods and theropods
are lizard-hipped dinosaurs; Stegosaurus is a bird-hipped dinosaur,
an early member of a group which became much more common and diverse
in the Cretaceous period.
Stegosaurus was an early armoured dinosaur and its defences
were formidable. Later armoured dinosaurs were veritable living
tanks, some even had armoured eyelids!
The lion of
A giant, weighing
more than 20
Up to 30 metres
long, it has a
It feasts on
bugs on the
A carnivore with
2 long clawed fingers.
plates run down
© 1999 ABC, BBC
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to see how the Earth has changed in the last 152 million years.
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