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.


Baluchiterium - Creator:Dmitry Bogdanov -


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  • 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