when did amphibians begin to colonize land as the first terrestrial vertebrates
Vertebrate land invasion The aquatic to terrestrial transition of vertebrate organisms occurred in the late Devonian era and was an important step in the evolutionary history of modern land vertebrates. The transition allowed animals to escape competitive pressure from the water and explore niche opportunities on land. Fossils from this period have allowed scientists to identify some of the species that existed during this transition, such as Tiktaalik[1] and Acanthostega.[2] Many of these species were also the first to develop adaptations suited to terrestrial over aquatic life, such as neck mobility and hindlimb locomotion.
Mesozoic The era began in the wake of the Permian–Triassic extinction event, the largest well-documented mass extinction in Earth's history, and ended with the Cretaceous–Paleogene extinction event, another mass extinction which is known for having killed off non-avian dinosaurs, as well as other plant and animal species. The Mesozoic was a time of significant tectonic, climate and evolutionary activity. The era witnessed the gradual rifting of the supercontinent Pangaea into separate landmasses that would eventually move into their current positions. The climate of the Mesozoic was varied, alternating between warming and cooling periods. Overall, however, the Earth was hotter than it is today. Dinosaurs appeared in the Late Triassic and became the dominant terrestrial vertebrates early in the Jurassic, occupying this position for about 135 million years until their demise at the end of the Cretaceous. Birds first appeared in the Jurassic, having evolved from a branch of theropod dinosaurs. The first mammals also appeared during the Mesozoic, but would remain small—less than 15 kg (33 lb)—until the Cenozoic.