I can remember vividly the first time I opened a package of toys labeled as "dinosaurs", and pulled out a figure that I knew was NOT a dinosaur. It was a Dimetrodon. My disappointment only grew larger as I got older, and found manufacturers mislabeling other creatures as dinosaurs. Pterosaurs, plesiosaurs, and other prehistoric reptiles often get tossed into a bin labeled "dinosaur." But the Dimetrodon upset me the most. See, Dimetrodon wasn't even CLOSE to being a dinosaur. First of all, the last Dimetrodon died 40 MILLION YEARS before the FIRST true dinosaurs existed. Secondly, dinosaurs, birds and modern lizards all share a common reptilian ancestor who was a Saurapsid. Dimetrodon was a Synapsid - the only living Synapsids are Mammals. Yes, Dimetrodon was a proto-Mammal. Maybe now you can see why its inclusion in a bucket labeled "Dinosaurs" upset me so much. The last shared ancestor that Dimetrodon and the first dinosaur lived about 70 million years before the dinosaurs. Sadly, you would not have difficulty finding a package of toy "dinosaurs" at a store near you that has a definite non-dinosaur contained inside. I wonder if paleobiologists ever write cease and desist letters?