This giant beast is Elasmotherium, sometimes called the Siberian unicorn.

That hump over its shoulders isn't just for show - it's packed with muscles that allow it to lift and maneuver its massive head and horn, rather like a bison does.

The unicorn comparison goes farther than just the horn. Compared to other rhinoceroses, their legs are longer and more suited to running. I've yet to see one do magic,though...

Some paleontologists have suggested that Elasmotherium's head and hump were not muscular enough to carry a giant horn, arguing in favor of more of a lighter... unicorn-stump. However, those that we've created in the park have proved strong enough to carry any sized horn. The size really depends on which mutations were present in the prehistoric "donors" DNA.