Researchers have discovered a new species of giant dinosaur that has been called Meraxes gigas: just like the Tyrannosaurus rex, M. gigas has very short forelimbs, and it seems that both of these massive dino theropods evolved the trait separately.
An artist's impression of Meraxes gigas. shows never seen before, complete regions of the skeleton, like the arms and legs that helped us to understand some evolutionary trends and the anatomy of carcharodontosaurids,"Based on an analysis of fossil bones recovered in the northern Patagonia region of Argentina, the researchers determined that the dinosaur they'd discovered was 45 years old when it died, about 11 meters long, and weighed more than four tons.
The question is: what were its short arms used for? From the skeletal remains, it's clear that the forelimbs had strong muscles, so it's apparently not through a lack of function that the arms shrunk down to a smaller size.