amphibians
Amphibians were the first animals to have true lungs and limbs for life on land. However, they still had to return to water to reproduce. Thats because their eggs lacked a waterproof covering and would dry out on land. The first fully terrestrial vertebrates were amniotes. Amniotes are animals that produce eggs with internal membranes. The membranes let gases but not water pass through. Therefore, in an amniotic egg, an embryo can breathe without drying out. Amniotic eggs were the first eggs that could be laid on land.