Paleozoic Era: Devonian Period

419–359 Ma

The Devonian: exploration onto land

Of the most important developments in the Devonian, none stand out as plainly as the earliest tetrapodomorphs diverging from lobe-finned sarcopterygian fish and making their way onto riverbanks. In the backdrop here, we can see the primitive Tiktaalik, not yet a tetrapod (four-legged animal) but more equipped for terrestrialization than other fishes of the time, emerging on the shoreline. Swimming nearby is a group of Scaumenacia, a genus of lungfish (a group within the sarcopterygians) with the ability to breathe air. Because we know that vascular plants and several arthropod clades had made their way onto lab in the short-lived Silurian Period, these novel tetrapod-like organisms had plenty of resources to exploit when they, too, made their journeys. Within the Devonian, several of the land plants had evolved leaves and root systems, and true seed-bearing plants appeared by the end of the periodall of which show the continuation of the Silurian-Devonian Terrestrial Revolution. and the co-evolution of plants and arthropods. In general, terrestrial environments were becoming greener through the Devonian Period, and newly evolved root systems were contributing to soil production and changes in patterns of erosoin and sediment supply. The trees in the background with fern-like leaves are amongst the earliest known, belonging to the progymnosperm genus Archaeopteris, not to be confused with the famous later feathered avian dinosaur, Archaeopteryx, though the spelling and pronunciation are quite similar! In the marine realm, great coral reefs of were comprised of colonial tabulate and rugose, or horn, corals, the latter of which reached their peak diversity during this period. Although exceptionally preserved coleoids from the Carboniferous Bear Gulch Lagerstätte in Montana are amongst the oldest agreed-upon shell-less cephalopods in the fossil record, there are some disputed fossils known from one of the most famous Devonian-aged lagerstätten, the Hunsrück Slate of Germany. Several unique fishes are observed here as well, including the shark-like Stethocanthus, known for its bold anvil-shaped dorsal fin, and one of everyone's favorite of the ancient apex predators (though probably not taking the crown), Dunkleosteus, with its heavily armored dermal bone skull and trunk. The bite force that Dunkleosteus could apply is considered to have been the highest of any living or extinct fish—and among the strongest in the animal kingdom. The end of the period was marked by a series of at least three extinction pulses that together are considered one of the big five extinction events, known collectively as the Late Devonian extinction