Triassic facts for kids

Kids Encyclopedia Facts

Quick facts for kids Triassic
251.902 ± 0.024 – 201.4 ± 0.2 Ma PreЄ Є O S D C P T J K Pg N
A map of Earth as it appeared during the Norian age of the Late Triassic
Chronology
Triassic graphical timeline -255 — – -250 — – -245 — – -240 — – -235 — – -230 — – -225 — – -220 — – -215 — – -210 — – -205 — – -200 — Pz Mesozoic Permian]] Triassic]] Jurassic]] ET]] Middle]] Late]] Induan]] Olenekian]] Anisian]] Ladinian]] Carnian]] Norian]] Rhaetian]] ← Triassic–Jurassic extinction event ← Scleractinian corals & calcified sponges ← Carnian pluvial episode ← Manicouagan impact ← Coals return ← Full recovery of woody trees ← Smithian–Spathian boundary event ← Permian-Triassic extinction event Subdivision of the Triassic according to the ICS, as of 2024. Vertical axis scale: Millions of years ago
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Period
Stratigraphic unit	System
Time span formality	Formal
Lower boundary definition	First appearance of the conodont Hindeodus parvus
Lower boundary GSSP	Meishan, Zhejiang, China 31°04′47″N 119°42′21″E / 31.0798°N 119.7058°E / 31.0798; 119.7058
Lower GSSP ratified	2001
Upper boundary definition	First appearance of the ammonite Psiloceras spelae tirolicum
Upper boundary GSSP	Kuhjoch section, Karwendel mountains, Northern Calcareous Alps, Austria 47°29′02″N 11°31′50″E / 47.4839°N 11.5306°E / 47.4839; 11.5306
Upper GSSP ratified	2010

The Triassic Period was a very important time in Earth's history. It lasted about 50.5 million years. This period began around 251.9 million years ago and ended about 201.4 million years ago. It was the first and shortest period of the Mesozoic Era, often called the "Age of Reptiles."

The Triassic started and ended with huge extinction events. These events dramatically changed life on Earth. During this time, many new animals appeared. Some of these animals would later rule the planet. Reptiles, especially archosaurs, were the main land animals. Dinosaurs first appeared in the Late Triassic. However, they became truly dominant in the next period, the Jurassic.

What's in a Name? The Triassic Story

The name "Triassic" was given in 1834 by a scientist named Friedrich August von Alberti. He noticed three distinct layers of rock in southern Germany. The name comes from the Greek word triás, meaning 'triad' or 'group of three'.

These three rock layers are:

The lower layer: called Buntsandstein, which means "colorful sandstone."
The middle layer: called Muschelkalk, meaning "shell-bearing limestone."
The upper layer: called Keuper, meaning "colored clay."

Early Triassic sandstone (Buntsandstein) near Stadtroda, Germany
Middle Triassic Muschelkalk (shell-bearing limestone) near Dörzbach, Germany
Late Triassic Steigerwald Formation and overlying Hassberge Formation in Schönbuch, Germany

Triassic Time: Early, Middle, and Late

Scientists divide the Triassic Period into three main parts. These are the Early Triassic, the Middle Triassic, and the Late Triassic. Each part had its own unique climate and types of life.

Earth's Changing Face: Paleogeography

During the Triassic, all the major continents were joined together. They formed one giant supercontinent called Pangaea. This huge landmass stretched from the North Pole to the South Pole.

Pangaea was surrounded by a vast ocean called Panthalassa. The climate across Pangaea was mostly hot and dry. Large deserts covered much of its interior. However, as the Triassic ended, Pangaea slowly began to break apart. This led to a more humid climate in some areas. The breakup created two new landmasses: Laurasia in the north and Gondwana in the south.

Triassic Climate: Hot and Dry

The Triassic climate was generally very hot and dry. There was no ice at either pole. Instead, the polar regions were moist and mild. This allowed forests and animals to thrive there.

Pangaea's enormous size meant that the ocean had little effect on its inner climate. Summers were very hot, and winters were cool. This big difference between the land and ocean caused strong monsoons. These were like giant seasonal storms.

The Early Triassic was one of the hottest times in Earth's history. This was due to massive amounts of greenhouse gases released by huge volcanic eruptions. While generally dry, the Triassic also had periods of increased rainfall. One famous rainy period was the Carnian Pluvial Event. This event brought widespread humidity across the globe.

Triassic Plants: Life on Land

Triassic plants as imagined by artists in the late 1800s.

After the Permian-Triassic extinction, the plant world slowly recovered. In the Early Triassic, plants called lycophytes became very common. Some, like Pleuromeia, grew tall, up to 2 meters (6.5 feet).

Later in the Triassic, new plant groups became important. These included the Bennettitales, an extinct group of seed plants. In the southern lands of Gondwana, the tree Dicroidium was very common. Ginkgoales, which today only has one living species, also diversified. Conifers, like pine trees, were abundant.

The Mystery of the Coal Gap

Interestingly, there are almost no coal deposits from the very beginning of the Triassic. This is known as the "Early Triassic coal gap." It's thought to be part of the Permian-Triassic extinction event. Scientists believe that the harsh conditions after the extinction, like acid rain or extreme heat, made it hard for plants to form peat swamps, which eventually become coal.

Triassic Animals: A World of Reptiles

Middle Triassic rock layers in southwestern Utah.

The Triassic Period saw an amazing recovery and diversification of animal life.

Marine Invertebrates

In the oceans, new types of corals appeared. They formed small reefs. Ammonites, shelled creatures related to squid, recovered and diversified. Bivalves, like clams, also became very common.

Insects

Aquatic insects rapidly diversified during the Middle Triassic. Many modern insect groups began to appear during this time.

Fish Life and Reproduction

Birgeria, a large predatory fish from the Triassic.

After the Permian-Triassic extinction, fish species were quite similar worldwide. Coelacanths, ancient fish still alive today, were very diverse. Ray-finned fish also diversified greatly. The first teleosts, which are the most diverse group of fish today, appeared. Large predatory fish, like Saurichthys and Birgeria, were successful. Lakes and rivers were home to lungfish, like Ceratodus.

Amphibians: Giants and Newcomers

A reconstruction of the giant Triassic amphibian Mastodonsaurus.

Some amphibians, called temnospondyls, survived the extinction. These were mostly aquatic or semi-aquatic. Some, like Mastodonsaurus, grew to be huge, up to 6 meters (20 feet) long!

The first modern amphibians, called Lissamphibians, also appeared. These included the ancestors of frogs, salamanders, and caecilians. However, they didn't become common until the Jurassic.

Reptiles: The Rise of Archosaurs

The Triassic was truly the age of reptiles. After the extinction, archosauromorph reptiles rapidly diversified.

Archosauromorphs: Diverse Forms

Some early archosauromorphs, called protorosaurs, had very long necks. Tanystropheus had a neck longer than its body! Others, like sharovipterygids, could even glide using their long hindlimbs.

Rhynchosaurs were barrel-bodied plant-eaters. They were very common in the Middle Triassic. Allokotosaurs were iguana-like reptiles. Trilophosaurus was a common example with special teeth.

A group called archosauriforms were active predators. They had serrated teeth and walked upright. Large erythrosuchids were top carnivores in the Early Triassic. Phytosaurs were common in the Late Triassic. These long-snouted, semi-aquatic predators looked a lot like modern crocodiles.

True Archosaurs: Dinosaurs and Croc Relatives

True archosaurs split into two main groups. One group, Avemetatarsalia, led to birds. The other, Pseudosuchia, led to crocodiles.

Avemetatarsalians were not very common at first. But they eventually gave rise to the first pterosaurs (flying reptiles) and dinosaurs in the Late Triassic. Early long-tailed pterosaurs quickly spread worldwide. Triassic dinosaurs included early long-necked plant-eaters (sauropodomorphs) and meat-eaters (theropods). Most Triassic dinosaurs were small predators, like Coelophysis.

Pseudosuchians were much more dominant. They included large plant-eaters like aetosaurs, which were heavily armored. Giant carnivores, sometimes called "rauisuchians," were the top predators. They were like the T-Rexes of the Triassic. These "rauisuchians" were ancestors to the smaller crocodylomorphs, which were the only pseudosuchians to survive into the Jurassic.

Tanystropheus, a long-necked tanystropheid
Proterosuchus, a crocodile-like early archosauriform from the Early Triassic
Staurikosaurus, one of the earliest dinosaurs, a member of the Triassic family Herrerasauridae
Postosuchus, a rauisuchid which was an apex predator in parts of Late Triassic North America
Plateosaurus was one of the largest of early sauropodomorphs, or "prosauropods", of the Late Triassic
Coelophysis was one of the most abundant theropod dinosaurs in the Late Triassic

Marine Reptiles: Masters of the Sea

Marine vertebrate apex predators of the Early Triassic and Anisian (Middle Triassic).

The Triassic oceans were home to many types of marine reptiles. These included the Sauropterygia, like pachypleurosaurs and nothosaurs. The first plesiosaurs also appeared. The lizard-like Thalattosauria and the very successful ichthyopterygians (fish-like reptiles) diversified quickly. Some ichthyopterygians grew to be very large.

Other Reptiles: Turtles and More

The earliest turtles, such as Proganochelys, appeared in the Late Triassic. Other interesting reptiles included the drepanosaurs. These were unusual, chameleon-like tree-dwelling reptiles with bird-like heads.

Synapsids: The Ancestors of Mammals

Three groups of therapsids, often called "mammal-like reptiles," survived into the Triassic. These were dicynodonts, therocephalians, and cynodonts. The carnivorous cynodont Cynognathus was a top predator in Gondwana.

However, during the Triassic, archosaurs largely replaced therapsids as the dominant land animals. This "Triassic Takeover" may have pushed the surviving therapsids and their early mammal relatives to live as small, mostly nocturnal creatures. This nocturnal life might have helped them develop fur and a higher metabolism. The first true mammals evolved from advanced cynodonts during the Late Triassic.

Lystrosaurus was a widespread dicynodont and the most common land vertebrate during the Early Triassic, after animal life had been greatly diminished
Cynognathus was a carnivorous mammal-like cynodont from the Early Triassic.

Fossil Treasures: Lagerstätten

Lagerstätten are special fossil sites where fossils are incredibly well-preserved. Two Early Triassic lagerstätten, the Guiyang biota and the Paris biota, show us how life recovered after the Permian-Triassic extinction.

The Monte San Giorgio lagerstätte, located in Italy and Switzerland, was a lagoon in the Middle Triassic. Its deep, oxygen-poor waters helped preserve fish and marine reptiles perfectly.

The End of an Era: Triassic–Jurassic Extinction

The mass extinction event is marked by 'End Tr'.

The Triassic Period ended with another major mass extinction. This event hit ocean life especially hard. Many marine reptiles disappeared, except for ichthyosaurs and plesiosaurs. Many types of invertebrates were also severely affected.

On land, many large archosaur reptiles and amphibians died out. Some early, primitive dinosaurs also became extinct. However, the more adaptable dinosaurs survived. This extinction event cleared the way for dinosaurs to become the dominant animals on Earth. This led to the true "Age of Dinosaurs" in the following Jurassic and Cretaceous periods.

The exact cause of this extinction is still debated. It happened around the time of massive volcanic eruptions. These eruptions formed the Central Atlantic Magmatic Province (CAMP). This was one of the largest volcanic events in Earth's history. These eruptions released huge amounts of gases, causing rapid climate change and ocean acidification. While a bolide (asteroid) impact was once considered, evidence suggests that any known impacts happened too early to be the direct cause.

Skull of a Triassic Period phytosaur found in the Petrified Forest National Park

Images for kids

View of the Tethys area during the Ladinian stage (230 Ma)
230 Ma continental reconstruction
Sydney, Australia lies on Triassic shales and sandstones. Almost all of the exposed rocks around Sydney belong to the Triassic Sydney sandstone.