Lobe-finned fishes facts for kids
Quick facts for kids SarcopterygiiTemporal range: Latest Silurian – Recent
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| Coelacanth, Latimeria chalumnae | |
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Sarcopterygii
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The Sarcopterygii are a special group of fish called lobe-finned fish. You might know some of them, like the lungfish and coelacanths. They are a type of bony fish that first appeared a very long time ago, about 418 million years ago (mya) in the Silurian period. What makes them super important is that one branch of these fish eventually evolved into tetrapods, which are all the four-limbed animals that live on land, including us!
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What Makes Lobe-Finned Fish Special?
These fish have unique paired fins that are rounded and look a bit like early limbs. These special fins are a big clue that they might be the ancestors of land animals. All sarcopterygians also have teeth covered with real enamel, just like ours!
When we talk about a "clade" in biology, it means a group that includes an ancestor and all of its descendants. So, the Sarcopterygii group includes all the Tetrapods. This means all species of four-limbed vertebrates are part of this group. The fin-limbs of these fish are very similar to what scientists believe were the first forms of limbs in tetrapods. The ancestors of land animals can be found among the lobe-finned fish from the Devonian period. Scientists sometimes use the cool term 'fishapod' for these amazing transitional animals that show how life moved from water to land.
How Lobe-Finned Fish Evolved
Sarcopterygians and their relatives, the Actinopterygii (or 'ray-finned fish'), together form the superclass Osteichthyes, which are known as 'bony fish' because they have a skeleton made of bone, not cartilage. However, lobe-finned fish and ray-finned fish have many differences in their fins, how they breathe, and how their blood moves around.
The very first sarcopterygians, found about 418 million years ago, looked a lot like the Acanthodii, which were 'spiny fish' that are now extinct. In the early to middle Devonian period (about 416–385 mya), when large, armored fish called placoderms ruled the seas, some sarcopterygians started to move into freshwater places.
Around 416–397 mya, the sarcopterygians split into two main groups: the Coelacanths and the Rhipidistia. The coelacanths stayed in the oceans. They were very common between 385 and 299 mya. Today, we still have coelacanths living in the oceans, like the Latimeria species.
The Rhipidistians, whose ancestors probably lived in ocean areas near river mouths (called estuaries), left the ocean and moved into freshwater. They then split into two more big groups: the lungfish and the tetrapods. The lungfish were amazing! They developed the first simple lungs and limb-like fins. Around 397–385 mya, they learned how to live outside of water. They used their stubby fins to walk on land to find new water if their pond dried up, and they used their lungs to breathe air. Lungfish were most diverse during the Triassic period, but today there are only a few types left.
The first tetrapodomorphs, which included huge fish like the rhizodonts, had a similar body plan to lungfish, who were their closest relatives. But these fish didn't leave the water until later in the Devonian period (385–359 mya), when the first tetrapods (four-legged vertebrates) appeared. Tetrapods are the only tetrapodomorphs that survived after the Devonian.
Other types of sarcopterygians that were not tetrapods continued to live until near the end of the Paleozoic era. Many of them died out during the huge Permian–Triassic extinction event about 251 million years ago.
Types of Lobe-Finned Fish
Here's a simplified look at how scientists group these fish:
- Sarcopterygii (Lobe-finned fish)
- Coelacanthimorpha (Coelacanths)
- Rhipidistia
- Dipnoi (Lungfishes)
- Tetrapodomorpha (Ancestors of tetrapods)
- †Rhizodontiformes
- Osteolepiformes
- Panderichthyida
Related Animals
- Actinopterygii – These are the 'ray-finned fish', which are the most common type of fish today.
Images for kids
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In the later Devonian period, descendants of ocean-dwelling lobe-finned fish — like Eusthenopteron — were followed by:
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Coelacanths are the only living sarcopterygians that still live in the ocean.
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Guiyu oneiros was the earliest-known bony fish, living about 419 million years ago. It had features of both ray-finned and lobe-finned fish, but is considered closer to lobe-finned fish.
See also
In Spanish: Peces de aletas lobuladas para niños
