What Did the Planet Look Like When Dinosaurs Walked the Earth?

When dinosaurs walked the earth around 250 million years ago, the planet looked very different than it does today. If one of those giant lizards suddenly popped up today, it would find our view of the earth very different from the one they remembered.

Most dinosaurs trod the earth from around 245 until 66 million years ago, in the Mesozoic Era, which was millions of years before the first recognizable humans appeared.

Scientists have split the Mesozoic Era into three separate periods: the Triassic, Jurassic, and Cretaceous. During each of these periods, the continents as we know them today looked very different from our modern world. 

Nothing would be the same, not the land or the seas or most vegetation.

This article will look at where the landmasses were, where the great ancient oceans lay, and how they created the fantastic beasts that we find in today’s fossils. We are using maps created by the geologist Dr. Ron Blakey and available on his website deeptimemaps.com.

Triassic Period (252 to 201 million years ago)

This map shows what the world looked like in the Late Triassic Period. Here we can see that earth contained one colossal landmass, the mega-continent known as Pangea. 

Pangea has one enormous shoreline extending from what we know today as the North Pole all the way down to the South Pole. Creatures could have walked all the way down this mega landmass, moving over all the continents that today are separated by large oceans.

Across the middle of Pangea, near the equator, lay a range of mountains that would rival today’s Himalayas. These were the Appalachian Mountains at their highest and most dramatic. This enormous mountain range divided Pangea into northern and southern sections and affected their vegetation.

The northern section carried vast deserts and broad basins that radiated out from the base of the mountains. The south was heavily forested, but the land was subjected to wild swings in weather, with some years being super wet and others super dry. Monsoon rains pounded this long coastline in some years and were missing in others. The dinosaurs that lived in this volatile environment were highly adaptable.

Further north, in what we would today see as Europe and Asia, the weather was more equable, and larger dinosaurs wandered these more northern plains. 

Further to the south, we find Gondwanaland, which was richly forested and today yields rich harvests of Triassic fossils—indicating that the land carried abundant animals.

Along the western coast, which would later become South America, some of the earliest and most complete fossils are found.

Fossils found in Antarctica show that during the Triassic, this was a warm and hospitable place in which to live.

The Triassic ended similarly to how it started with a dramatic change to the landmass and climate. 

Scientists believe that massive volcanic activity occurred, giving birth to what we know as the Atlantic Ocean. The process spewed vast amounts of carbon and sulfur dioxide into the air causing unimaginable climatic changes. 

It is thought the sea levels rose, and the sea became acidic, which led to the mass extinction of creatures living in the oceans. Many Triassic archosaurs, except the dinosaurs, crocodiles, and pterosaurs, died out entirely on land.

The oldest proven dinosaur fossils found to date were found in the  Ischigualasto Provincial Park in northwestern Argentina. These fossils date to approximately 231 million years ago and include Herrerasaurus, Eoraptor, and Eodromaeus remains. 

This left space for the surviving dinosaurs to evolve while the tiny mammals continued scurrying around on the floor of the forests.

Jurassic Period (200 to 145 million years ago)

This is the time that dinosaurs ruled the earth on the land, sea, and air.

Now, we can see the effect of the significant volcanic eruptions that occurred. We can see that Pangea has split along the Appalachian Mountains, and North America has pulled away. The Appalachians are still there along the coastline, but they have been severely eroded and are much smaller. 

North America continues to move northwest, pushing through the Pacific Ocean. As it makes its way through, it creates a significant new mountain range known as the Sevier Orogeny (orogeny means building mountains).

We can see that Europe and Asia have also separated into a broad swathe of islands. Africa and South America are still one mass in the south, with Australia and Antarctica locked together just above the south pole.

This was the first time the continents became isolated, and large oceans formed between them. This led to changes in the creatures living on them, as they began developing in isolation from each other. Early in the Jurassic, there were land bridges as there are similarities in the fossil record for this period. Later in the Jurassic, there are significant differences in the fossil records.

The temperatures were more moderate, but the carbon dioxide kept the temperature higher than today, and rainfall increased and became more widespread due to the seas appearing between the landmasses.

The increased rainfall encouraged plant growth, and ferns and tall conifers grew over vast tracts of land. Much of this vegetation became the source of the fossil fuels we suck out of the ground today.

The explosion of vegetation paved the way for the growth of large herbivores, such as the Brachiosaurus and the Diplodocus. These were some of the largest creatures ever to walk the face of the earth, and by the end of the Jurassic, vast herds of these creatures dominated the world, along with the carnivores that preyed on them.

Cretaceous Period (145 to 66 million years ago)

The most striking thing is that now we see that most of the continents have been isolated, and the oceans as we understand them have primarily been created. India is still lying next to Madagascar, and North America exists as two pieces separated by a wide watery basin. 

The Sevier Orogeny has created an extensive mountain range along the western shoreline. The landmass to the west is called Laramidia, and the land to the east is called Appalachia.

Europe is still a series of islands in a warm, biologically rich seaway known as the Tethys Seaway that flows over today’s Middle East. This warm water flowed around the equator warming the entire planet.

Antarctica and Alaska have moved to their respective positions, but the fossil found in these places indicate that the poles were still warm places in which to live.

The world landmasses were now divided, and each region supported its own unique fauna.

Sea levels repeatedly changed during this time, and as the single-cell algae bloomed in the warm seas around Europe, their skeletons fell to the seafloor and built up thick layers of sediment, laying the foundations of the dense white chalk cliffs that we see today. Cretaceous comes from the Latin word “creta,” meaning chalk.

In addition to the dinosaurs that had survived, we now get more organisms starting to evolve. Flowering plants arrived to live beside cycads, ferns, and conifers. Insects, especially bees, began to emerge, snakes evolved, and mammals expanded to include tree climbers and more predators and the small ground-dwelling mammals.

End of the Mesozoic Era (66 million years ago)

This now looks close to our modern world. India still has to drift northwards to collide with Asia. Africa and Eurasia are still separated by the Tethys Seaway, eventually becoming the Mediterranean Sea.

Geologically North and South America have separated, but fossil records indicate some bridges had to have been in existence to allow small mammals to cross. They then separated again and did not become one until the Panama isthmus appeared a few million years ago, resulting in a significant exchange of creatures. 

This was the last Period of the extraordinary creatures we know collectively as dinosaurs.