The Genial Dinosaur — John Russell Fearn

Clifford Brooks and his wife Joan believe that 'Herbert,' the frisky dinosaur who'd saved their lives in A THING OF THE PAST, has been lost forever in the Earth's underworld. But to their amazement, he returns to the surface of the Earth--and immediately raises once again all of the complicated problems attendant upon trying to house a fearsome, 80-ton prehistoric beast in the midst of modern society. He's eventually condemned to death as a menace to the community, but somehow he--or his owners--always managed to circumvent the final sentence. Which is just as well, since it appears that Herbert's appearance is almost providential. When aliens from another star arrive to Earth bent on denuding the planet of one of its natural resources, only Herbert can save the day! Another delightful SF adventure from the pulp paperback era.