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The first land vertebrates, the Tetrapoda, appeared about 397 million years ago, near the middle of the Devonian Period. Despite having limbs rather than fins, early tetrapods were not completely terrestrial because their eggs and larvae depended upon a moist aquatic habitat. The first tetrapods apparently soon diverged; one lineage became the amphibians (which retained the requirement for moisture-associated reproduction), whereas a second lineage yielded the Amniota during the Early Pennsylvanian Epoch (318 million to 312 million years ago). Fossils of these early amniotes are lacking. However, they must have appeared at this time because, for the Middle Pennsylvanian Epoch ...(100 of 17436 words)