How do scientists know that utahraptor ever lived?

The Utahraptor, also known as “Utah’s predator” or “Utah’s thief”, is a kind of theropod dinosaur that lived on Earth during the Cretaceous period (over 125 million years ago).  Theropod dinosaurs, like Utahraptors and Velociraptors, are characterized by having hollow bones and three-toes limbs.  

The first specimen of Utahraptor was found by paleontologist Jim Jensen in east-central Utah in 1975, but scientists didn’t pay much attention to it at the time. It wasn’t until 1991, during an excavation in the north of Utah, that other scientist, Carl Limoni, found more fossils of the same kind of dinosaur discovered in 1975.  

Using these new sets of fossils, paleontologists James Kirkland, Robert Gaston and Donald Burge named this new specimen Utahraptor in 1993. Not very much of it was found though. These scientists just found a toe claw, hand claws, parts of the skull, a tibia and a few vertebrates, but these fossils were enough to confirm Utahraptor's existence.  

b. both have yearned to escape the environment they experienced as a child.