Crocodilians, along with birds, are the only survivors of the once-prevalent Archosauria. During the Mesozoic (245-65 million years ago), this group, including dinosaurs and other reptiles, dominated life on all continents and in the oceans. Most or all of crocodilians' adaptations had already evolved by the late Triassic (about 200 million years ago). Crocodilians are the most advanced surviving reptiles; many of their features are more similar to mammals or birds than to other reptiles. There are only a few members, and all modern crocodilians have adapted to a semi-aquatic life, although as recently as 3000 years ago there may have been a terrestrial crocodilian species on New Caledonia. Some crocodiles may venture into larger bodies of fresh or salt water, but all must lay their eggs on dry land. Most crocodilians live in the tropics. No crocodilians venture out of lowlands; it is speculated that none ever lived above 1000 meters (3260 feet) above sea level.