Dinosaurs lived on our plane for millions of years before they died out But we prehistoric reptiles is that their appearance was very short arms and some had horns on their head. Others had long arms with claws like long knives. In the 1960s palaeontologists found a pair of giant dinosaur arms in Mongolian. The length of each arm was 2.4 metres with claws that were 26 centimeters long whose arm were they though and what happened to the body for over 40 years scientists have bee looking for the answers to these questions. They called the mystery dinosaur deinocheirus which means terrible hand over the years there have been different theories about what kind of dinosaur it was some scientists believe is was some scientists believe it was a type of dinosaur that looked like an astrich and used its long. Arms to catch its when it hunted. Some palaeontologists estimates that this was a massive animals possibly as big Tyrannosaurus rex other it was it a smaller dinosaur with very long arms. Although they have examined the area where they found the arms many times. They only foND a few other bones looking like until someone find new evidence other fossil or bones there will be many unanswered questions and the deinocheirus will remain a mystery