Triassic Period


250 Million Years Ago  
Triassic Period

The period when the first dinosaurs appeared was called the “Triassic Period.” At that time, the Earth was much different than it is today.

During the Triassic Period, the climate was very hot and dry.  Mammal-like Reptiles dominated the land and some of them grew to lengths of almost 20 feet. Twenty foot monsters ruled the land. This was the time when dinosaurs evolved, according to the theory of evolution.

The first dinosaur, sometimes called the “dawn dinosaur,” was Eoraptor. It was about the size of a dog. An almost complete skeleton was found in Argentina in 1993. Scientists were delighted. The discovery of an almost complete skeleton of a dinosaur is a very rare find.


Eoraptor was a very fierce hunter, and a meat eater. It was fast and smart. It’s teeth were serrated (sharp and jagged). It was 1 foot (12 inches) high and 3 feet (approx. 1 meter) long. It weighed only 20 lbs. (9 kilos) It stood on its hind legs and had small, grasping hands. It looked a little like a miniature t-rex. Scientists believe it could walk on four legs, but speculate (think) it did so only if necessary. The skull was small, but strong. Its bones were hollow. Eoraptor had five fingers on its front limbs, which it used with skill.

Another early dinosaur called, “Herrerasaurus” (pronounced huh-Rare-uh-Sore-us), roamed Earth at the same time as Eoraptor. It is one of three dinosaurs that were found in South America. Come back next week to learn more about Herrerasaurus.




 Reptiles as the most dominant creatures on the planet. While not all of the Mammal-like reptiles vanished, they became vulnerable to the emerging dinosaurs. Many scientists believe that as the dinosaurs got bigger, faster and more ferocious, they killed most of the Mammal-like reptiles, and those that survived were the smallest of these creatures. Eventually, the only ones left were the very smallest and these evolved into early mouse-sized mammals.

 Dinosaurs begin to grow and diversify. The plant-eating dinosaurs, which appeared during the mid-to-late Triassic more than 200 million years ago, were the first Ornithischians, or bird-hipped dinosaurs, and were no bigger than turkeys. Huge ferns and other primitive non-flowering trees dominated the land. Grass never grew during the Triassic and the dinosaurs got bigger and bigger as a result of having little competition from any other forms of life on the land. One of the most significant developments to occur during the latter part of the Triassic was that some creatures took to the air. Two families of animals began to develop at this time - flying reptiles, or Pterosaurs, and the first members of the family that became birds.