During the Early Jurassic, animals and plants living both on land and in the seas recovered from one of the largest mass extinctions in Earth history. Life was especially diverse in the oceans—thriving reef ecosystems, shallow-water invertebrate communities, and large swimming predators, including reptiles and squidlike animals. On land, dinosaurs and flying pterosaursdominated the ecosystems, and birds made their first appearance. Early mammals also were present, though they were still fairly insignificant. Insect populations were diverse, and plants were dominated by the gymnosperms, or “naked-seed” plants.