1. Trilobites: These are extinct arthropods that were incredibly abundant during the Paleozoic. Their hard exoskeletons fossilized easily, making them one of the most common fossils from this era.
2. Brachiopods: These are marine animals with hinged shells. They were incredibly diverse during the Paleozoic, with many different shapes and sizes. Their fossils are common in Paleozoic rocks.
3. Crinoids: These are echinoderms, related to starfish and sea urchins. They had a stalk and a crown of feeding arms. Crinoid fossils, particularly the stem segments called "columnals," are frequently found in Paleozoic rocks.
The Paleozoic era was a time of great evolutionary change in the oceans, and these are just a few examples of the diverse life that existed then.