woolly mammoths look like elephants
sabre tooth tigers look like tigers now
elks are moose
and there's probably more

if you arch the back and reposition the legs on the second skeleton it would look pretty much like the first skeleton.

the first is a rat

and the second is a dinosaur called Marasuchus lilloensis

it has four legs so i reckon it would have ran around on all four legs instead of two hind legs as pictured.