Epoch 1
At the dawn of this era, a small comet impacted the ocean off the south-east corner of Panzerna with enough momentum to plough through kilometres of ocean in less than a second, and crash into the shallow ocean crust beneath. Huge tsunamis decimated the mountainous southern coast of Panzerna, leaving their mark in the geologic record with great boulders mixed with marine fossils piled ontop of the steep slopes, but the mountainous terrain largely shielded Iotania and the rest of the world from the full force of the impact.
The comet was not enough to cause a mass extinction, but it was the catalyst for a great volcanic upwelling in the sea floor, with the original crater soon being replaced by towering volcanic islands - which also happened to be rich in metals and minerals. Tectonic upheaval spread out along fractures in the crust, reaching eastern Panzerna and raising new island chains from the seabed.
A volcanic winter dawned, but was short-lived; within a century, the huge volumes of carbon dioxide were warming the planet far beyond the pre-impact average, and with this came both melting glaciers and increased rainfall; in many places, the survivors of primitive plants soon found themselves basking in abundant heat and rain. Within a few million years, primitive tropical rain forests had emerged across central Iotania - now splitting into two continents, Imperia and Topica.
Ocean life suffered from the release of volcanic poisons - many species of fish, mollusc, and sea scorpions went extinct, and amphibious Tetrapods went completely extinct from the shores of Panzerna. Sea scorpions, already under threat from ferocious giant armoured fish, never recovered and remain on the brink of extinction. For many other branches of life, recovery was swift, however; surviving branches of trilobites, with some radical new adaptations, saw an especially rapid recovery - some became covered in toxic spikes, and some became specialised for living around deep-sea vents, feeding on the creatures that thrived among the ‘hot smokers’, even while others now venture onto land in the form of several amphibious species.
Amphibious creatures of all kinds were aided by a rise in sea levels, flooding large areas of the continents and creating warm, shallow, nutrient-rich seas. In central Topica, these seas are now especially fertile, bordered by swampy rain-forests and hosting a huge variety of life. Here the Tetrapods flourish, branching into all manner of bizarre amphibians, as well as venturing inland in the form of recognisably lizard-like creatures which can live their adult lives entirely out of water - often in tree canopies or rock faces, hunting insects - though all still remain tied to the water for reproduction, not being true ‘amniotes’ yet.
Where the shallows meet the sea, and nutrients flow from the new rivers that are scouring the continents, new forms of aquatic algae are evolving - aided in part by the disruption to previous populations of herbivorous fish and molluscs. By the end of this era, underwater forests of primitive, towering kelp-like plants have taken root in places along the Topica, Imperia and Nessaria. Although the largest armoured fish died off by this point, smaller varieties survive, and some have become adapted for prowling the kelp forests and warm shallows with an almost crocodilian lifestyle, being apex predators of their habitats.
Panzerna is notably devoid of all Tetrapods, Amphibians and their descendants - partly due to isolation, partly due to the ongoing volcanism. It is however a stronghold of new, hardy, amphibious trilobites, and certain giant insects - all of which are growing larger due to increased oxygen; the flourishing of new forests, while acting as a sink for much of the carbon that was being released, also created new sources of oxygen, leading to a noticeably oxygen-heavy atmosphere. Even life forms without complex circulatory systems were able to growing larger in size. Topica in particular is home to giant millipede-like creatures - the first large herbivores; and by the end of the era, giant predatory insects - appearing like dragonflies, but over half a metre in wingspan - prowl the skies unchallenged over the tropical swamps and forest, spreading across the globe.
Nessaria is home to some of the remnant giant fungus species, which have not yet been overtaken by plants - these have developed sticky growths to trap insects, and have become carnivorous, helping them to flourish in otherwise infertile soils. Nessaria, with rather unpredictable weather, is also home to the most drought-resistant plants yet to evolve, with branching roots able to reach water below the topsoil.
The end of this era sees a new rise in temperature, as relentless volcanism in Panzerna continues to pump out carbon dioxide. Despite increased average rainfall, large parts of Topica remain scorched, barren desert, and these deserts only grow as the continent slowly drifted northwards... By now it was too warm for glaciers to form at the poles - ice was only seen at the tops of the highest peaks in the world - but the long polar winters are still death to primitive plant life. The peak of polar summers does see a blooming of life in northern Topica, with migrations of giant flying insects on land and fish feeding on plankton blooms in the shores, but currently only a few small plants and moss species can survive the long dark night here. As Topica heads relentlessly north, it seems more of this continent will share this fate.
Nessaria and Imperia are heading for an imminent collision, while the Panzerna plate seems to be largely stationary.
[notes, questions answeres and stat updates to come - for now, I sleep!]
I can give you volcanic eruptions or a comet impact (or both) if you really want.
