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Dinosaurs
With a number of famous films on Dinosaurs, the word is familiar to most people.
The word, Dinosaur, owes its origin to a Greek word and it means "Terrible
Lizard". These prehistoric land reptiles lived in the 'Age of Reptiles'.
They were the masters of the earth for hundreds of millions of years, till they
became extinct around 65 million years ago. Though the reasons for the mass extinctions
are yet being debated, the most probable cause is a cataclysmic collision of a
giant meteorite with the earth. The resulting damage and changes to the atmosphere
and food sources was too great for the Dinosaurs to survive.
The era in which the Dinosaurs lived was called the Mesozoic Era, which is
sub-divided into three smaller periods called the 'Triassic' period - 254 to
204 million years ago; 'Jurassic' period - around 204 to 140 million years ago
and the 'Cretaceous' period - which was 140 to 65 million years ago. A large
variety of Dinosaurs lived during the entire Mesozoic Era. Dinosaurs of the
'Triassic' period were mainly plant eaters but towards the 'Cretaceous' period
most were meat eating predators.
Though Dinosaurs were reptiles, there is evidence to suggest that they were
partly warm blooded and they did not entirely depend on the warmth of the sun
for regulating their temperature. Due to this, they did not have to alternate
between the Sun and shade, as often as modern day reptiles.
Dinosaurs are different in physical characteristics when compared to other
reptiles. Some of them walked on two legs and moved about in a partially upright
position. Others used all four legs for locomotion. Some were slow and heavy
while others though heave were fleet footed. This ensured that they were able
to chase down their prey using speed. Dinosaurs used a variety of methods to
protect themselves. Some had armor plated structures; while some grew horns,
spikes, crests, frills etc. Some of the Dinosaurs had thick, bumpy skin. A few
Dinosaur fossils have been found with rudimentary feathers and wings. They were
the ancestors of modern birds.
There is a major difference in skeletal structure between Dinosaurs and modern
reptiles. The legs of a Dinosaur were directly beneath the hip and this enabled
them to walk upright. A modern reptile such as a crocodile had the top section
of their limbs joined at the hip horizontally, while the section below the knee
went straight down towards the ground. This gave the crocodiles a sort of low
gait as if they were dragging themselves on their bellies. The jaw muscles of
a Dinosaur were well developed. Their hip, knees and ankles were also well developed
for movement and some of them, in spite of their size, could move very fast.
When we compare the movement capabilities, modern day reptiles seem to have
regressed, compared to their prehistoric cousins.
Dinosaur names were derived from Latin or Greek and usually were
descriptive of the Dinosaur's appearance or place where they were found. Of
all the Dinosaurs, the Tyrannosaurus Rex is the most popularly known. It was
a fast giant, which walked upright on sturdy hind limbs and was a voracious
killer. On the other hand, the herbivorous Apatosaurus, more popularly known
by its misnomer 'Brontosaurus', was a giant quadruped with a slow, lumbering
gait. The prehistoric land reptiles ruled the earth for hundreds of millions
of years and were well adapted to the land they lived on.
Dinosaur List