As many ten year olds could tell you, Triceratops is not a mammal and has only a rough resemblance to a rhinoceros. Who says there are dog-like dinosaurs? The “famous” creatures you refer to are not dinosaurs, but “mammal-like reptiles” (Dimetrodon being one example) that lived in the Permian and Triassic periods, some of which evidently evolved into mammals. See: http://www.talkorigins.org/indexcc/CC/CC215.html