Why round animals are rare on land ???

  I know millipedes curl themselves when they are threatened.

Armadillos and pangolins also go round only to protect themselves.  Then they will unroll to move  !!!

On land, animals need strong legs and long bodies to survive.

There are 3 reasons why round animals are rare on land  -----

1.  Round means rolling. But we can not control where we roll !!!

       Land animals require to run, climb, walk and dig.

       That's why land animals evolved legs instead of round bodies   !!!

2. Round shape has smallest surface area.

    It is best to keep heat inside.

     But land animals need to dump heat as they run.

    That's why land animals evolved legs instead of round bodies  !!!

3.  Round animals don't have limbs.

       They can not  reach or grab.

      Land animals need to move faster to escape from predators.

       That's why land animals evolved legs instead of round bodies  !!!