Jehol biota facts for kids
The Jehol biota was an amazing collection of living things. It included all the plants and animals that lived in northeastern China a very long time ago. This was between 133 and 120 million years ago. Imagine a whole ancient ecosystem from the Lower Cretaceous period!
We know about the Jehol biota because of the many fossils found there. These fossils are mostly from two special rock layers. They are called the Yixian Formation (about 125–121 million years ago) and the Jiufotang Formation. Scientists also think some fossils from this time are found in North Korea.
The Jehol area was full of wetlands and many lakes. It wasn't a place with big rivers or oceans. The weather was seasonal, meaning it changed between dry and wet periods. The climate was temperate, not too hot or too cold. Sometimes, volcanoes to the west would erupt. They would cover the land with ash, which changed the ecosystem for a while. The name Jehol was given to this area when Japan occupied parts of China from 1933 to 1946.
The Jehol biota is super important to scientists. This is because they have found so many different kinds of fossils there. Plus, there are huge numbers of fossils for each species. This helps us learn a lot about ancient life.
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Amazing Ancient Life: Diversity of the Jehol Biota
The Jehol biota is like a treasure chest of ancient life. It has many species that scientists thought had died out much earlier. For example, the dinosaur Sinosauropteryx and the pterosaur Dendrorhynchoides were found here. These were previously only known from the Upper Jurassic period.
Even a very old type of mammal-like reptile, called a tritylodont therapsid, was found. Scientists thought these creatures had disappeared in the Middle Jurassic. But they were still around in the Jehol biota!
This area also has the earliest and most basic members of groups that later spread worldwide. These include new types of ceratopsians (like Triceratops), therizinosaurs, tyrannosaurs, and oviraptors.
Plants and Animals of the Jehol Biota
The Jehol biota has given us fossils of all sorts of plants and animals. These include:
- The earliest flowering plants
- Different types of algae like charophytes
- Snails (gastropods) and clams (bivalves)
- Lots of tiny water creatures like conchostracans and ostracods
- Shrimps, insects, and spiders
- Fish, frogs, and salamanders
- Turtles, choristoderes (crocodile-like reptiles), and lizards (squamata)
- Pterosaurs (flying reptiles)
- Many kinds of dinosaurs, including dinobirds (dinosaurs closely related to birds)
- The largest mammals known from the Mesozoic Era
- A huge variety of birds, including the earliest advanced birds. Some were the smallest and largest birds known from the Mesozoic.
Ancient Forests and Water Plants
The forests around the lakes were mostly made up of conifer trees. These included types of podocarp pines, araucarias, and cypresses. There were also ginkgos, bennettitaleans (extinct cone-bearing plants), ephedra, horsetails, ferns, and mosses.
The leaves and needles of these trees show they could handle dry seasons. But some ferns and mosses usually grow in very wet places. It's possible they grew very close to the water to avoid dry conditions. A plant called Archaefructus is thought to be the earliest known flowering plant. Scientists believe it was a water plant.
How Fossils Were Preserved in Jehol
The fossils from the Jehol biota are incredibly well preserved. They have been found in special places called Lagerstätten. This German word means "storage place" and refers to sites with amazing fossil preservation. The two most famous Lagerstätten in Jehol are the Yixian and Jiufotang Formations.
Not only are there many fossils, but they are also very detailed. Often, the skeletons are still connected (articulated). You can even see soft tissues, color patterns, what was in their stomachs, and twigs with leaves and flowers still attached!
Paleontologists (scientists who study fossils) have learned two main things from this:
- First, the animals and plants from the land must have been washed into the lakes very gently. Or, they were already in the lakes when they died. Their bodies don't show damage that would happen from big floods.
- Second, volcanic ash is often found mixed with the lake sediments. It seems that ashfalls quickly buried the dead organisms. This created anoxic (oxygen-free) conditions around them. This stopped scavenging animals from eating the bodies. It also prevented bacteria from breaking them down. This helped the fossils stay so well preserved.
Scientists believe the Jehol biota might have reached as far as North Korea. Its earliest fossils might be in another Chinese Lagerstätte, the Huajiying Formation.
Yixian Formation: A Fossil Hotspot
The Yixian Formation is a rock layer in Liaoning, northeastern China. It is famous for its outstanding fossil preservation. This formation has layers of siliclastic (sand and silt) sediment mixed with basalt (volcanic rock).
The Japanese first identified this formation when they occupied Manchuria (the "Jehol" area). The rocks here were formed about 125–121 million years ago. This is where the famous Confuciusornis birds were found. Sinodelphys, the earliest known metatherian mammal (like a marsupial), was also discovered here.
Jiufotang Formation: Feathered Dinosaurs and Early Birds
The Jiufotang Formation is another important rock layer in Liaoning from the Lower Cretaceous period. It has given us amazing fossils of feathered dinosaurs, early birds, pterosaurs, and many other creatures.
For a long time, scientists debated the exact age of the Jiufotang Formation. Estimates ranged from the Upper Jurassic to the Lower Cretaceous. But dating methods using argon confirmed its age. It is about 120.3 million years old. Fossils of Microraptor and Jeholornis come from this formation.
Huajiying Formation: The Earliest Jehol Fossils?
The Huajiying Formation is also from the Lower Cretaceous, but its exact age is still being studied. It is likely the oldest of the Jehol biota Lagerstätte sites. It contains layers of sediment mixed with volcanic ash. Fossils of birds, dinosaurs, and fish have been found here.
Images for kids
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Confuciusornis from the Jehol biota
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Jeholornis. This is a small theropod, not a bird.
See also
In Spanish: Biota de Jehol para niños
