Acanthodii facts for kids
Quick facts for kids AcanthodiiTemporal range: Early Silurian - Permian
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| Different extinct fishes of Early Devonian | |
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Acanthodii
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Climatiiformes |
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Acanthodii (say: Ah-kan-THOH-dee-eye) were a group of ancient fish. People sometimes call them spiny sharks because they had strong, sharp spines on their fins. These fish lived a very long time ago, from about 430 million years ago (in the Early Silurian period) until about 250 million years ago (in the Late Permian period).
Acanthodians are special for two main reasons. First, they were some of the earliest known vertebrates (animals with backbones) that had jaws. Second, their fins were supported by thick, unmoving spines, much like the dorsal fin of a modern shark.
Contents
What Were Spiny Sharks?
Acanthodii were a class of fish that are now extinct. This means they no longer exist on Earth. They had features that were a mix of both bony fish and cartilaginous fish.
Bony and Cartilaginous Features
- Bony fish (Osteichthyes) have skeletons made mostly of bone. Most fish you know today, like salmon or goldfish, are bony fish.
- Cartilaginous fish (Chondrichthyes) have skeletons made of cartilage. Cartilage is a tough, flexible material, like what's in your nose or ears. Sharks and rays are examples of cartilaginous fish.
Acanthodians had some traits from both these groups, making them unique.
Where Did They Live?
The very first acanthodians lived in the ocean. But as time passed, especially during the Devonian period, many species started living in freshwater. This means they could be found in rivers and lakes.
Key Features of Acanthodians
These ancient fish had some distinct characteristics that help scientists identify them.
Jawed Vertebrates
Acanthodians were among the first known jawed vertebrates. Before them, most vertebrates did not have jaws. Jaws were a huge step in evolution because they allowed animals to bite and chew food. This meant they could eat a wider variety of things.
Spiny Fins
One of the most noticeable features of acanthodians was their strong, fixed spines. These spines supported their fins. Unlike many modern fish whose fins can move a lot, the spines of acanthodians were stiff and did not move. This is why they are often called "spiny sharks."
When Did Spiny Sharks Live?
Acanthodians had a long history on Earth.
Early Beginnings
They first appeared about 430 million years ago. This was during the Early Silurian period. At this time, life was mostly in the oceans.
Peak and Decline
During the Devonian period, many different types of acanthodians lived. This was a time when fish were becoming very diverse. However, by the end of the Permian period, about 250 million years ago, all acanthodians had died out. This was part of a huge extinction event that affected many forms of life.
Images for kids
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Three acanthodians from the Early Devonian of Great Britain: Mesacanthus (an acanthodiform), Parexus (a "climatiiform"), and Ischnacanthus (an ischnacanthiform)
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Impression fossil of the diplacanthid Rhadinacanthus longispinus, at the Museum für Naturkunde, Berlin
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Nerepisacanthus, a Silurian acanthodian known from decent fossils
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Various acanthodians, from top left clockwise: Cheiracanthus, Acanthodes, Climatius, Ischnacanthus, Parexus, Gyracanthus. center: Diplacanthus.
See also
In Spanish: Acantodios para niños
