It is obvious that different models were used for certain wide shots of the beast, as it lacks the skin texture of the larger model and its claws aren't colored.
The footage of the stampeding cattle is obviously sped up.
In closeups of the beast's feet walking, their shadows reveal the top edges of the fake feet. Also, the beast's tail is absent in these shots.
When the horse, scared by the dinosaur, throws Enrique off, smoke from the gunshot that scared the horse is visible on the right side of the frame.
When Jimmy yells at Sarita to run for the cliffs, he fires at the beast. Smoke comes from the barrel, but the gun makes no sound.
Near the end when Panchito is looking around the swamp for his father as the beast stalks him, in one shot a huge filming camera is very blatantly visible among the bushes in the screen's left bottom corner as the kid walks by.
What happened to Enrique? After Jimmy saved his life and Enrique decided Jimmy was alright, Jimmy left him at the opening of the cave and we never saw him again. Usually, at the end of a movie like this, someone like Enrique would be seen again at the end when they have achieved their victory.