Story, first published: Stellar #3 (1977)
An artist is sent through a rift of time to the age of the dinosaurs. He and other social misfits have been shanghaied to alternate worlds by the bosses of the prime world's "managed society." The alternate worlds are being exploited by big business interests from the prime world. A race of intelligent dinosaurs assures the artist that they will get rid of the invaders and protect the other alternate worlds from a similar fate.
Ewald, Robert J.: When the Fires Burn High and the Wind is from the North, p.118