Prehistoric Mammals Much Bigger Than They Are Today
After the age of dinosaurs had ended about 65 million years ago mammals became the largest animals to roam the earth. Rhinos and elephants however were much larger than they are today.
Huge mammals weighed almost 17 tons. The biggest mammal of our age , the African elephant, by comparison , weighs only about 6.5 tons.
When dinosaurs roamed the earth mammals were small creatures that stayed the same in size for over 150 million years. The journal Science claims that after dinosaurs had become extinct , mammals became larger and larger but then stopped growing.
In the 1990s, a French team discovered prehistoric fossils in Baluchistan, the area between Iran, Afghanistan and Pakistan. The fossils belonged to an extinct hornless rhinoceros , the Baluchitherium , which lived about 40 million years ago. It was 5 meters tall and had the size of three elephants.
Scientists are not sure how mammals got that big. During the age of dinosaurs they often had to fight for food and served as food for the giant reptiles themselves. When the dinosaurs disappeared nobody was there to eat the leaves of trees and plants. For the first time mammals had plenty of food to eat.
Why mammals stopped growing is still a mystery. One theory claims that continents became smaller and there wasn’t enough land available . According to other experts, a colder climate led to the death of dinosaurs. Mammals grow best in cold weather because bigger animals can conserve the heat better.
Related Topics
- Age of Dinosaurs
- World of Mammals
- Prehistoric Animals
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- New Mamal Species Discovered in South American Andes
Words
- according to = as said by …
- age = era, time
- available = to be used; to be had
- claim = to say that something is true
- comparison = contrast
- conserve = keep, save
- creature = a living thing
- disappear = vanish, go away
- discover = to find something for the first time
- extinct = to die out
- fossil = an animal or plant that lived thousands or millions of years ago; the shape of such an animals and plant has been preserved in rock
- giant = very big
- however = but
- huge = very , very big
- journal = magazine
- lead – led = cause
- mammal = type of animal that drinks milk from its mother’s body when it is young
- plenty = a lot, enough
- prehistoric = a time in history when nothing was written down
- reptile = type of animal like a snake or lizard , whose body temperature changes; it lays eggs to have babies
- rhino = short for “rhinoceros”
- rhinoceros = a large heavy animal with a thick skin and one or two horns on its nose
- roam = walk around
- scientist = a person who is trained in science and works in a laboratory
- serve as =here: were
- size = how big something is
- sure = certain
- weigh = how heavy something is