Answer: When it's two movies edited together.
I saw this on the video shelf and thought, "Oh, good. Another low-budget dinosaur movie. Haven't seen one of those since Carnosaur 3." So I rented it and sat down to watch it. The first scene opens with three teenagers riding around the desert in a jeep. "Well," I thought, "This is sort of like that scene in Carnosaur." Then I realized, it WAS that scene from Carnosaur. At first, I thought they gave me the wrong tape, but this was a scene from the middle of Carnosaur, not the beginning. Actually, it was my favorite scene from Carnosaur. Now I was seriously disappointed. Instead of watching a new dinosaur movie, I had been tricked into watching clips from two old dinosaur movies edited together. The other reviewers of this movie miss one point in their otherwise on-target reviews. The movie doesn't just use stock footage in place of special effects; it exists for the sole purpose of using stock footage in place of special effects. The script was only added to string together scenes from the first two carnosaur movies. Every line of dialogue exists only to explain why these completely unrelated events are popping up like plastic gophers in a Chuck-e-Cheese game. If you want dinosaurs, rent the Carnosaur movies again.