247 MILLION YEARS AGO

Following the horrendously massive extinction at the end of the Permian period, methane levels in the atmosphere fluctuated widely from the expected normal levels of around 2,200 parts per million. The fluctuations occurred sometime between 278 million and 250 million years ago, consisting of 5 major peaks with the first one being the biggest reaching around 4,400 parts per million.

During these exceptionally high methane peaks and subsequent global warming conditions, the interior of the great supercontinent appeared more desert-like because conditions on land were hot and dry. Only the coastal regions remained sufficiently humid to support ground-covering ferns, tall tree-like ferns such as Dicroidium, conifers and cycads, and an increasingly more diversified and flourishing insect population.

Then the methane peaks eventually subsided for conditions to cool down and rainfall increased. Over the next million years, the plants edged their way once again towards the interior of the supercontinent until much of the land became a huge tropical forest, thereby stabilising the fluctuations in climate from the methane, and helping to store enough carbon dioxide in the atmosphere inside the trunks of the trees.

245 MILLION YEARS AGO

In the same way the plants expanded across the continents, there was a similar expansion in animal numbers over the next few million years. Nothing unusual here, except what differed in this sudden burst (in geological terms) in life compared to the Cambrian period was the greater numbers of animals of a particular theme rather than an all out innovative stage of evolution.

As Roger Lewin, author of Complexity: Life at the Edge of Chaos, wrote:

"...there have been tremendous bursts of innovation...in the history of life, mostly in the wake of mass extinctions. For instance, following the Permian extinction some 250 million years ago, in which an estimated 96 percent of existing species perished, the rate of innovation almost matched that of the Cambrian. But the innovation was principally variations upon existing themes; no major new themes were added. In the Cambrian, by contrast, innovation was largely at the level of producing new themes, with variations upon them being relatively minor." (1)

235 MILLION YEARS AGO

With many new predators competing for the abundant supply of food on land, a number of reptiles and a few mammal-like animals decided to return to the sea. Those other animals brave enough to stay put evolved to have features designed to increase their survival rate. (2)

Among the land-based creatures that successfully evolved at this time included the first true hairy-like mammals and the first dinosaurs (the name comes from the two Greek words deinos, "terrible", and saurous, "lizard"). However, it would be the dinosaurs who would dominate life on the great supercontinent (known as Pangaea) for the next 170 million years.

Evidence to support the existence of this great supercontinent can be seen from the fossil evidence. The fossils show animals of the Triassic Period were widespread and remarkably alike throughout all the continents of the world. But later, after the supercontinent broke up during the Jurassic Period at around 210 million years ago (and with further isolation of animal communities as the seas rose in the early Creataceous period), the animals diversified into more unique forms based on locality.

232 MILLION YEARS AGO

For more than a million years, rains fell regularly across the single continent. A lushes forest supporting an abundance of life can be seen over the entire landmass. But climate was abut to change for the worse at around this time.

Before the Carnian Pluvial Episode began 232 million years ago, Pangea was already a land of extremes. Its enormous size meant that moisture from the oceans rarely reached the interior, leaving vast stretches of desert and semi‑arid plains under a hot, high‑CO₂ atmosphere. Coastal regions were more forgiving: strong seasonal monsoons brought periodic rains, feeding conifer forests, river systems, and fern‑rich wetlands. Inland, however, the climate was harsh. Dune fields stretched for hundreds of kilometres, vegetation was sparse, and life clustered around scattered river valleys and oases. This was the world early dinosaurs, amphibians, and reptile lineages inhabited—stable enough to support life, but dominated by dryness.

Everything changed when massive volcanic eruptions from the Wrangellia Large Igneous Province began releasing enormous quantities of greenhouse gases into the atmosphere. Global temperatures rose sharply, and the hydrological cycle intensified. Instead of the predictable monsoons of earlier Triassic times, Pangea was suddenly drenched by millions of years of episodic, torrential rainfall. These wet intervals came in pulses lasting hundreds of thousands of years, transforming landscapes that had been dry for ages. Deserts contracted, lakes expanded, and floodplains spread across regions that had rarely seen standing water. Sediments from this time shift abruptly from red desert sandstones to dark, water‑rich mudstones—geological proof of a world overwhelmed by rain.

But the wet phase did not last. As volcanic activity continued, CO₂ levels climbed even higher, pushing global temperatures upward and destabilizing atmospheric circulation. The rains weakened, then failed, and Pangea swung back toward intense aridity. This drying period was severe enough to collapse many of the ecosystems that had flourished during the wet interval. Forests died back, freshwater habitats shrank, and soil erosion stripped landscapes bare. Amphibians, reptiles, and plant groups adapted to stable moisture suffered heavily. Roughly 10–20% of species disappeared, marking a significant—though not catastrophic—extinction event. The drought lasted long enough to reshape entire biomes, leaving behind a world that looked very different from the one that had existed before the climatic upheaval.

Yet the aftermath was not bleak. As volcanic activity waned and atmospheric conditions stabilized, rainfall patterns gradually returned to a more balanced state. Forests re‑established themselves, river systems recovered, and food webs rebuilt with new species at their core. Dinosaurs, once minor players, began to diversify rapidly in the newly opened ecological niches. Modern conifer forests spread widely, and early mammals found space to thrive. The world after the Carnian Pluvial Episode was more humid, more vegetated, and far more dynamic than the one before it—a transformed landscape that set the stage for the rise of the dinosaurs and the ecosystems of the Jurassic.

Mammals did indeed emerge around the same broad interval as the climatic upheavals of the Carnian Pluvial Episode, though their origins slightly predate the droughts themselves. The first true mammals—tiny, nocturnal, insect‑eating creatures descended from cynodont synapsids—appeared roughly 233–231 million years ago, right as the climate was oscillating between extreme rainfall and severe drying. They were not abundant yet, but their arrival coincided with a period when many older Triassic animal groups were declining. During the Carnian crisis, an estimated 10–20% of species disappeared, especially large amphibians, specialized herbivores, and reptile lineages that depended on stable freshwater or predictable vegetation. Animals that could survive with less water, tolerate heat, or exploit patchy food sources had a clear advantage. Small body size, burrowing habits, and flexible diets helped many survivors endure the drought.

Early mammals fit this pattern well. They were generalists: able to eat insects, small invertebrates, and possibly seeds or plant matter when needed. Their high metabolic rates and fur allowed them to remain active at night, avoiding daytime heat and conserving moisture. Other survivors—early dinosaurs, small reptiles, and adaptable herbivores—also tended to be species capable of living on limited water and shifting diets. In this sense, the Carnian Pluvial Episode acted as an evolutionary filter. It removed many specialized Triassic animals and favored those with broad ecological tolerances, including the earliest mammals, which quietly persisted and diversified in the ecological gaps left behind.

230 to 201 MILLION YEARS AGO

The Sun is known to take approximately 225 million years to travel one revolution around the Milky Way. Thus nearly one revolution around the galaxy ago, the Earth was just starting to be dominated by the dinosaurs.

The early dinosaurs were small creatures by our standards, but they later evolved into some of the largest land animals that ever lived. Part of the reason for these changes included a new hip structure in the predators allowing these animals to bring their legs closer together and lift the entire body with greater ease compared to those older animals whose legs came out the side and scuttled around. As a result, these predators could move more quickly. Indeed, some predators became so confident in their new hip structure that a few evolved the ability to run almost entirely on two legs with the remaining limbs becoming nothing more than mere stumps. For the plant-eating animals, they had no choice but to evolve to better survive the onslaught from these predators. This included the development of tough armour plating along the spine, neck and head region, turning large tails into lethal weapons, and simply to gain greater size to overwhelm the predators. Other plant-eaters may choose to stay small and agile and would use the vegetation to hide or camouflage itself as the best form of defence. During these evolutionary changes over the next 50 million years, huge plant-eating dinosaurs like the Apatosaurus (formerly called Brontosaurus), Briachiosaurus and Sauropods, and large terrifying meat-eaters such as the Tyrannosaurus Rex roamed the Earth.

This was a time when size did matter. Not only was there a plentiful supply of food on the great supercontinent to support very large dinosaurs on land — a kind of giant "smosgasbord" of fresh meat and vegetation just sitting out there ready for the taking — not to mention the extra phosphorus in the soil from the rich volcanic soils to support thick and large bone structures in plant-based dinosaurs and later the predators, and the fact that the atmosphere had an oxygen level of between 30 and 35 per cent to support bigger muscles and a heavy mass for animals, but also there was a survival bonus: the larger the animal can become, the more easier it is for the animal to survive the attack of most predators. Brings back memories of the reason why single-cells came together in the first place to form multicellular lifeforms. To improve chances of survival from a predator attack: losing a few cells from a bite won't matter too much. Painful, yes. But still likely to survive. And so it is the case for some plant-eating dinosaurs of this period. Being large is beautiful and bold at this time.

Despite size being an important factor in the survival of many dinosaurs, they had one major weakness: the reptiles did not develop a quick and effective internal body temperature-regulator. Not a major issue for the dinosaurs as there would be an extremely persistent period of very warm, moist tropical-like climate existent throughout much of the world for at least the next 50 million years. Even at nightime, the temperatures were balmy and pleasant.

Mammals, on the other hand, did develop a primitive internal body temperature-regulator suggesting that they were adapting to the lower temperatures existent at the extreme northern and southern latitudes on Earth, on mountain-tops, deep inside certain caves, and/or during the night where the great dinosaurs were probably more sluggish or kept themselves around lakes and shallow inland seas (which would have absorbed a lot of heat during the day), thereby allowing the mammals to remain hidden from view. Those mammals that did become nocturnal, remained small but their eyes and ears became more enlarged and sensitive to the darker environment.

Land-based mammals of this era were almost certainly small creatures living secretly and did not evolve into larger more complex creatures until the great dinosaurs disappeared.

NOTE 1: A large mammal would be too much of a target for the highly developed and powerful muscle structure of the two-legged carnivorous dinosaurs which gave these terrible lizards excellent speed (in a roughly straight line for the larger predators) to capture practically all large, cumbersome prey. Mammals of this era had to remain small and agile. (3)

NOTE 2: Mammals are not the only creatures to develop fur on their skins. Some smaller dinosaurs living in the temperate and polar regions also developed filaments of hair. These filaments became more abundant and colourful as a means of attracting a female partner. Eventually a point came when enough of these filaments allowed some lightweight dinosaurs to jump up in the air and glide, and later to use the heavily feathered front limbs to create enough force to push the animals through the air and achieve lift. We call these animals birds. Apart from the crocodiles and some other small reptiles, birds are the only dinosaur species to survive to this day.

NOTE 3: A day on Earth today might be 23.56 hours. However, in the Jurassic period, a typical day was equivalent to 23 hours.

201.3 MILLION YEARS AGO

The end of the Triassic Period was marked by one of Earth’s major mass extinction events. This global crisis coincided with the initial rifting of the supercontinent Pangaea, a process that triggered immense volcanic activity across what is now known as the Central Atlantic Magmatic Province (CAMP). These eruptions released vast quantities of carbon dioxide and other gases into the atmosphere, driving intense global warming, ocean acidification, and ecological instability. As a result, roughly 76% of all marine and terrestrial species disappeared, including many marine invertebrates, conodonts, ammonoids, and several reptile groups on land.

The environmental upheaval was severe but not instantaneous. Although the volcanic activity spanned hundreds of thousands of years, ecosystems began to stabilize relatively quickly afterward in geological terms. Over the next 1 to 2 million years, surviving plants and animals expanded into newly available ecological niches. On land, early dinosaurs, crocodylomorphs, pterosaurs, and mammals—groups that were comparatively less affected—rose to greater prominence as competing species vanished. Floral communities also underwent major restructuring, with many plant groups declining while others adapted to the altered climate.

With the Triassic‑Jurassic extinction complete, Earth entered the Jurassic Period, a time when dinosaurs would rapidly diversify and become the dominant terrestrial vertebrates for the next 135 million years.