Allosaurus is a species of theropod dinosaur from the Jurassic. It appeared in four Sunday strips and a story arc.
6/27 through 7/7 1990 story arc
Allosaurus also appeared in this 1990 story arc. In it, Calvin and Hobbes had traveled back in time 140 million years on a photo safari. They came across Diplodocus, Stegosarus, and an Allosaurs – all of which had actually died out by 140 Ma BC. The Allosaurus was hostile to the time travelers, who only narrowly managed to escape.
Calvin the Allosaur
Allosaurus made a number of appearances as a minor recurring alter ego of Calvin's.
Calvin, the Awful Allosaur
Calvin the Allosaur (identified as "Calvin, The Awful Allosaur")