It was the first film to feature the make-up work of special effects artist Stan Winston, for which he shared the 1973 Emmy Award for Outstanding Achievement in Makeup.
They are shown a skeleton of a large creature with wings and horns at a place called Uncle Willie's Desert Museum.
That night, two gargoyles, appearing much smaller than the skeleton and without horns or wings, invade the motel room to retrieve the skull.
Diana returns to the police station and pleads for the bikers' innocence but the deputy says only a judge can release them after charges have been filed.
The gargoyles rip the passenger door off and kidnap Diana, then overturn the car rendering Dr. Boley unconscious.
He tells Diana that they have only been alive for a few weeks after a 500-year incubation, and that humans have repeatedly killed them off in the past, but he vows that they will survive this time.
The gargoyle leader has a queen, who also has wings and speaks, and she informs him that "men, horses, and dogs" are approaching the cave, and that many more eggs will hatch the next day.