Triassic

A long time ago, the world was very hot.

Most land was in one big piece. It was a giant land called Pangaea.

Much of this land was a dry desert. Many new animals lived during this time. Giant water animals lived in the sea.

The very first dinosaurs also appeared. Later, the world changed again. Many animals died out at the end. This made room for dinosaurs to rule.

The Triassic was a time long ago. It lasted for 50.5 million years.

During this time, most land was one giant piece. We call this supercontinent Pangaea. The world was mostly hot and dry. Huge deserts covered much of the land.

Many new animals lived then. Reptiles were the main animals on land. Some were called archosaurs. This group included the first dinosaurs. Dinosaurs appeared in the Late Triassic. They did not rule the world yet. Other archosaurs could fly. We call these flying animals pterosaurs.

In the water, new fish appeared. Giant amphibians also lived in the sea. Some were large predators. Even the first tiny mammals appeared. These small animals would survive for a long time.

At the end, the world changed. A major extinction event happened. Many groups of animals died out. This helped dinosaurs become the leaders of the next era.

As the time ended, Pangaea began to break apart. It split into two big pieces. One was in the north. The other was in the south.

The Triassic was a very important time in Earth's history. It was the first part of the Mesozoic Era. This period lasted for 50.5 million years. It began about 251.902 million years ago. It ended when the Jurassic Period started 201.4 million years ago. This era started right after a huge extinction event. That event changed almost everything on our planet.

During this time, the world looked very different. Most of the land was joined together. This giant piece of land was called Pangaea. It sat right near the equator. Much of the middle of Pangaea was hot and dry. Huge deserts covered a lot of this land. As the period went on, Pangaea began to break apart. It split into two pieces called Laurasia and Gondwana.

Many new kinds of life began to grow. Reptiles were the most important animals on land. A group called archosaurs was very common. Some archosaurs were ancestors of crocodiles. Others were the very first pterosaurs that could fly. The first dinosaurs also appeared during the Late Triassic. They were not the bosses of the world yet. They would wait until the next period to rule.

Other animals were also finding their way. The first tiny mammals appeared during this time. These were small creatures called mammaliamorphs. In the water, new kinds of fish were spreading. Some fish lived in fresh water and some lived in the sea. Giant amphibians called temnospondyls were also large predators in the water. These animals lived through many big changes.

We know about this time because of rocks. A scientist named Friedrich August von Alberti named it. He did this in 1834. He looked at three different layers of rock in Germany. These layers were sandstone, limestone, and clay. The name Triassic comes from a Greek word meaning a group of three. This helps us remember the three rock layers.

Scientists divide the Triassic into three parts. They call these the Early, Middle, and Late Triassic. Each part has its own special fossils. The end of the period was very hard for many living things. Another major extinction event happened at the very end. This event wiped out many groups of animals. It cleared the way for dinosaurs to take over.

The Triassic is a major geologic period that shaped the modern world. It is the first and shortest period of the Mesozoic Era. This period lasted for 50.5 million years. It began 251.902 million years ago at the end of the Permian Period. It concluded 201.4 million years ago when the Jurassic Period started. The Triassic is also the seventh period of the Phanerozoic Eon. This era began immediately following the Permian–Triassic extinction event. That event had significantly reduced the biosphere of Earth.

Geologists divide the Triassic into three distinct epochs. These are the Early Triassic, the Middle Triassic, and the Late Triassic. Scientists often refer to the corresponding rock layers as the Lower, Middle, and Upper Triassic. The name itself has a specific historical origin. In 1834, Friedrich August von Alberti named the period. He chose the name after observing three distinct rock layers in southern Germany. These layers are the Buntsandstein, which is colorful sandstone. They also include the Muschelkalk, a shell-bearing limestone. Finally, there is the Keuper, which is composed of colored clay. The term comes from a Greek word meaning a triad or a group of three.

During this time, the Earth's geography was dominated by a supercontinent called Pangaea. This massive landmass stretched from the north to the south polar regions. It was centered near the equator. The Paleo- and Neo-Tethys oceans were located within the arc of Pangaea. Beyond the supercontinent lay the vast Panthalassa Ocean.

During the Late Triassic and Early Jurassic, Pangaea began to rift apart. It split into two large landmasses. These were Laurasia in the north and Gondwana in the south. This movement changed the global climate significantly. While the interior of Pangaea was mostly hot and dry with many deserts, the climate became more humid as the landmasses drifted apart.

The Triassic biosphere was defined by three categories of organisms. These included animals that survived the previous extinction, animals that flourished briefly, and new animals that evolved to dominate the Mesozoic Era. Reptiles were the primary terrestrial vertebrates. A specialized group called archosaurs was very successful. Some archosaurs were pseudosuchians, which were relatives of modern crocodilians. Other archosaurs became the pterosaurs, which were the first vertebrates to achieve flight. The first dinosaurs appeared during the Late Triassic. However, they did not become the dominant animals until the Jurassic Period.

Other groups also underwent major changes during these millions of years. Therapsids had been the dominant vertebrates in the Permian. In the Triassic, dicynodonts and cynodonts saw a brief surge in diversification. However, most therapsids declined and faced extinction by the end of the period. Interestingly, the first stem-group mammals, known as mammaliamorphs, appeared during this time. These were a specialized subgroup of cynodonts. They survived the eventual extinction and later radiated during the Jurassic.

Life in the water was also highly diverse. The earliest known neopterygian fish appeared near the start of the Triassic. This group includes early holosteans and teleosts. These fish quickly became dominant in both freshwater and marine habitats.

In the water, amphibians were represented by temnospondyls. These were giant aquatic predators that survived the end-Permian extinction. They saw a burst of diversification before going extinct at the end of the Triassic. Meanwhile, early crown-group lissamphibians, such as stem-group frogs and salamanders, became more common.

The end of the Triassic was marked by a major mass extinction event. This is known as the Triassic–Jurassic extinction event. This event wiped out many groups of animals, including most pseudosuchians. This loss of competition allowed dinosaurs to assume dominance in the following Jurassic Period. The geological changes were also driven by intense volcanic activity. The Siberian Traps eruptions persisted into the Early Triassic. Later, the Central Atlantic Magmatic Province was active during the Late Triassic. These events helped set the stage for the shifting oceans and continents of the future.