A little more than a year ago, in the corner of a Salt Lake City tattoo parlor spattered with sci-fi ephemera and fantasy art, I watched as artist Jon McAffee inked an Allosaurus onto my arm.

Allosaurus was the most common large carnivore of the Late Jurassic in North America. It was a smaller predecessor of the Cretaceous Tyrannosaurus. Strong forelimbs with sharp claws, powerful hind ...