The ancestors of dinosaurs were a group of reptiles called "Crurotarsi". These reptiles lived in the early Triassic period, about 230 million years ago. At that time, they were not like the crocodiles we know now, but more like other types of reptiles. Most of these reptiles were quadrupeds, like modern crocodiles or lizards. These animals generally have strong bodies and tails, sharp teeth and claws.
During this long evolutionary process, due to environmental changes, natural selection and gene mutations, the crocodiles gradually changed and differentiated into different branches. Among them, dinosaurs are a branch, and they gradually evolved into giant animals that walked on two legs.
In short, dinosaurs evolved from another existing branch of reptiles, and their evolutionary history is very complicated. The specific details still need to be revealed through research in fossil records and genetics.
