Explanation:
Animals lived in the water during the Mesozoic and on land in the Paleozoic. Animal complexity increased during the Paleozoic while the first flowering plants appeared in the Mesozoic era. ...
The Paleozoic era, not the Mesozoic era, had the first dinosaurs. The first mammals emerged in the Paleozoic era, not the Mesozoic era. The Mesozoic era, not the Paleozoic era, had the first animals with shells.
