Great Things have Small Beginnings
The Paleozoic Era had ended. For approximately a million years, fragments of life wavered on; recuperating from what was the greatest mass extinction ever in history. A dawn of a new era was approaching. The C-shaped supercontinent Pangea was still in formation, but the climate was very much dry, having the hottest summers polarising with the coldest winters in the continental interior. However, the Triassic period was a time of much diversifying of species in both water and land.
The Great Dying had left a massive scar on life, especially on the marine population where 95% was wiped out, alongside 70% of land animals. So what happened? What brought about those titanic beasts we know today?
The End of the Paleozoic Era birthed the “The Age of Reptiles”, known as the Mesozoic Era. Only two groups of land creatures survived the genocide they suffered, known as the Therapsids [descendants of the Synapsids], the mammal-like reptiles, and the more reptilian Archosaurs [descendants of Sauropsids]. At first, the dominant species that walked the Earth was a particular genus called the Lystrosaurus, the largest land creature at existence in the early Triassic.
They were the only large land animals to survive the extinction event and became the most populated land animal to live on the Earth for a short time. Smaller than the Dimetrodon, they lived vegetarian life-styles having beaks to cut off leaves rather than teeth and specially having small tusks as key features of their body. However, these sedate creatures gradually died out while the Archosaurs concurrently thrived and became the new dominant land vertebrae animals.
While there are multiple theories for this change, the most probable one would be the fact that Archosaurs were much better conservers of water than the Therapsids especially in such dry, arid and hot conditions. Like modern reptiles such as crocodiles, there’d be good reason to believe that like their descendants Archosaurs excreted Uric acid as paste rather than Urea as mammals do, rationing water much more efficiently.
The main Archosaurs that roamed the Earth in the Triassic were the Crurotarsi and the Onithodira. The Crurotarsi were crocodile-like, having either sprawled legs or fully erect limbs. One of its genus, the Rauisuchians, were the apex terrestrial predators. They were the later species of Crurotarsi that had fully erect limbs, and unlike crocodiles had an “upright stance”. The largest ever discovered species of Rauisuchians was measured more than 6 metres in length, on par with the larger Saltwater Crocodiles’ sizes.
Mind you the Saltwater Crocodile is the largest living reptile species as of now, except the Rauisuchians stood taller than all of them. It’s frankly terrifying and makes it quite clear why it was the leading predator of the Triassic!
However the other species was the Onithodira, the true ancestors of the dinosaurs. What differentiated the Crurotarsi from the dinosaurs were the way their femur and pelvis were organised, which the Onithodira did share with the dinosaurs. Unlike other Archosaurs, they were lightly built, with long S-curved necks and most were bipedal, travelling on two legs like the modern day birds. They were at this stage typically small in size and stature, but were predicted to be faster than the Rauisuchians due to their flexible hips and lightweight bones.
Such an example would be Coelophysis, which through excavations in Mexico, revealed their instincts to hunt in packs. Their long necks, sharp teeth and claws, bony tails [for stability] along with their lightweight body for speed provided them the perfect tools to be fast and deadly predators, accentuated by their large numbers. However, they perhaps were also cannibalistic as some researchers discovered smaller bones of the species in the fossils of Coelophysis. One defining trait of these Onithodires was that they had ‘advanced mesotarsal’ ankles, which provided them more balance when running but only allowed them to travel in one plane of direction, like a hinge of a door.
Later in the Triassic, the Onithodires species expanded into the Pterosaurs, the infamous flying reptiles that roamed the skies of Mesozoic Earth. The first Pterosaurs were tiny in size, e.g. the Sharovipteryx, which were the size of the common Crow. It was bipedal, wherein its tiny clawed front limbs were used to grasp their prey as they’d glide from tree to tree.
Marine life since the Permian Era was however simple. There were uniform fossil fish, meaning very few species of sea creatures, survived. This however soon changed as reptiles called Ichthyosaur, which were lizard-like, integrated themselves into the water. Originally writhing and moving their bodies side to side to travel in water, they evolved into dolphin-like creatures and were great in size.
Rather than moving their entire bodies side to side, they used their tails as sources of propulsion in water and hunted in the seas as air-breathers. By the mid Triassic, they were the dominating species in water and grew up to sizes of 15 metres+. This particular genus was the Shonisaurus which weighed approximately 30 tons, the weight of 30 Great White Sharks!
However all these new creatures that evolved from the end of the Permian Era and through the Triassic was just the beginning. These already incredible creatures were just the ‘prototypes’ and the Neanderthals to our human race of the even more monstrously enormous beasts that roamed later on Earth.