Saw Journey to the Center of the Earth on HBO on Demand last night. The Dimetrodons looked a little off. Wiki has this:"The giant Dimetrodons depicted at the center of the Earth action sequence were actually rhinoceros iguanas with large, glued-on make-up appliances added to their backs."
The Dimetrodons precede dinosaurs by about 40 million years. They are not reptiles. Wiki again: "Dimetrodon is assigned to the "stem-mammals" or "non-mammalian synapsids", a group traditionally called "mammal-like reptiles"."
