The Gondwanan supercontinent to the south, Siberia to the north, and the early creation of the small Euramerican supercontinent in the center dominated the paleogeography.
When it comes to vertebrates, the diversity of the jawed fish (gnathostomes) grew in fresh and saltwater, while that of the jawless armored fish (ostracoderms) fell.
In the early Devonian Period, armored placoderms were common; they went extinct in the late Devonian, possibly due to competition with other fish species for food.