Laid down during the , ~415 to ~360 million years ago.

The oldest fossil tetrapods are of animals that can be described, essentially, as , though more precisely they were more closely fish-like creatures that had developed some ability to both support their weight on land and to do so on what legitimately can be described as .

The Devonian period, a.k.a., the "", is found in the middle of the Paleozoic era, which in turn is found near the beginning of the Phanerozoic eon.

It actually isn't a contradiction that the first non-fish vertebrates would arise during the age of fish since, in fact, these first tetrapods were very much part of the of (the , i.e., as occurred during Devonian period.