Tetrapods are four-limbed vertebrates that evolved from lobe-finned fish during the Devonian (395 million years ago), invading the land and ultimately leading to today's the amphibians, reptiles, birds, and mammals. Read more →
Amniotes are tetrapods (four-limbed vertebrates) whose eggs contain amnions, an adaption that keeps them from drying out on land; they first appeared during the Carboniferous. There are two main groups, synapsids and sauropsids (anapsids, diapsids, and euryapsids), which differ in their evolutionary history and their skull morphologies (specifically, the types of fenestrae or "holes" in the skull). For a much more detailed look at the evolution and taxonomy of aminotes, check out Palaeofiles from the University of Bristol.
This list briefly describes the creatures appeared (and not necessarily when they disappeared, if they did). Keep in mind that all of the creatures listed are marine, and most are soft-bodied invertebrates. Of course, this list doesn't even come close to covering all the Paleozoic creatures, just the ones I found worth mentioning -- if you think I missed one, let me know in the comments! Click on the images to enlarge; hover to see photo credit in alt-text (many are from Nobu Tamura). Read more →