Arthrodire facts for kids
Quick facts for kids Arthrodirus terrelliTemporal range: Devonian
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Arthrodira
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The Arthrodires (say: Ar-thro-DEERS) were a group of ancient, armored fish that are now extinct. They belonged to a class of fish called Placodermi, which means they had bony plates covering their bodies. These amazing fish lived during the Devonian period, which was a very long time ago, about 419 to 359 million years ago.
Arthrodires were very successful for about 50 million years. They lived in many different parts of the ocean. They filled many different roles, from tiny bottom-feeders to giant hunters.
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What Made Them Special?
The name "Arthrodire" comes from Greek words meaning "jointed neck." This is because they had a special movable joint. This joint was between the bony plates that covered their head and the plates that covered their body.
This joint was very useful for eating! When an Arthrodire opened its mouth, its lower jaw moved down. At the same time, its head shield moved up. This allowed them to open their mouths very wide to catch prey.
Instead of regular teeth, Arthrodires used the sharp edges of their bony plates to bite. Their eyes were also protected by a bony ring. This is a feature that some birds and ancient marine reptiles called ichthyosaurs also had.
Different Kinds of Arthrodires
Early Arthrodires, like a fish called Arctolepis, were heavily armored. They often had flat bodies.
One of the most famous and largest Arthrodires was Dunkleosteus. This fish was a true super-hunter! It lived at the very end of the Devonian period. Dunkleosteus could grow to be between 3 and 9 meters (10 to 30 feet) long. That's as long as a school bus!
But not all Arthrodires were giant. For example, the long-nosed Rolfosteus was only about 15 centimeters (6 inches) long. That's about the size of a small fish you might see today.
Life in the Devonian Seas
Some people used to think that Arthrodires were slow fish that just stayed at the bottom of the ocean. They thought these fish were not very good at competing with other, more advanced fish.
However, this is not true! During their time, Arthrodires were one of the most successful groups of vertebrates (animals with backbones). They were very diverse, meaning there were many different types of them. They lived in many different environments. They were everything from top predators to small animals that ate tiny bits of food from the seafloor.
Why Did They Disappear?
The Arthrodires were one of many groups of animals that disappeared during the mass extinctions at the end of the Devonian period. These were big events where many different types of plants and animals died out.
After the Arthrodires were gone, other fish, like sharks, began to grow and spread out. They took over the places in the ocean that the Arthrodires used to live in.
Images for kids
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Artist's reconstruction of the coccosteine arthrodire placoderm Coccosteus cuspidatus
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Lower jaw plate of Eastmanosteus pustulosus from the Middle Devonian of Wisconsin
See also
In Spanish: Artrodiros para niños
