Osteoglossiformes

Some fish have hard tongues. They are called bonytongues. These fish live in fresh water. You can find them in many lands. They live in Africa and Asia. They also live in Australia. Some live in South America.

These fish come in many sizes. One fish is very small. Another fish is very large. It can grow as big as a man.

Some of these fish use light sparks. They use these sparks to find food. This helps them sense things nearby. They are very special fish.

Some fish have very hard tongues. Their name comes from Greek words for bony tongues. These fish live in fresh water. You can find them in Africa and Asia. They also live in Australia and South America.

These fish come in many shapes. They also come in many sizes. The smallest is a fish called Pollimyrus castelnaui. It is only 1 cm long. The largest is the arapaima. It can grow to 3 meters long.

Some of these fish have a special way to find food. The African knifefish and elephantfishes are weakly electric fish. They use electric fields to sense things. This helps them find prey.

These fish have a different body than most other fish. In most fish, the gut goes to the right. In bonytongues, the gut goes to the left. This happens near the stomach and throat. They are a very old group of fish. They first lived on a land called Gondwana. This land broke apart a long time ago.

Some fish have very special bodies. Their name comes from Ancient Greek words for bony tongues. This name describes their hard, toothed tongues. These fish belong to a group called Osteoglossiformes. They are a primitive group of ray-finned fish. This means they are an older type of fish. Most of these fish live in fresh water. At least 245 living species live in fresh water today.

These fish have a unique way they work inside. In most fish, the gut goes to the right. The gut is the path food takes. In bonytongues, the path goes to the left. This happens near the stomach and the throat. This is a very different way to be built. Some fish even use electricity to find food. The African knifefish and elephantfishes are weakly electric. They use electric fields to sense their prey.

These fish have a very long history. They first evolved on a land called Gondwana. Gondwana was a huge land that broke apart. Because of this, they live in many places now. You can find them in Africa and South America. They also live in Australia and southern Asia. In 2008, scientists found new marine species too. These were found in the Danish Eocene Fur Formation. This shows the group is very diverse.

There are many different families in this group. The largest fish is the arapaima. It can reach 3 meters in length. The smallest fish is called Pollimyrus castelnaui. It is only 1 cm long. There are also butterfly fishes in the Pantodontidae family. The Mormyridae family includes the elephantfishes. The Gymnarchidae family has the African knifefish. These fish come in many different shapes and sizes.

Learning about these fish helps us see how life changes. They show us how animals can live in different ways. Some use hard tongues to eat. Others use electric fields to feel the world. Their bodies show us how old life can be. They remind us of the huge land of Gondwana. Even small fish can tell a big story. They are a wonderful part of our world.

Osteoglossiformes is a unique order of ray-finned fish. Their name comes from Ancient Greek words meaning "bony tongues." This name refers to their specialized, hard tongues. These fish are considered a primitive group. This means they represent an older lineage of fish. Most of the at least 245 living species live in freshwater. They are found across South America, Africa, Australia, and southern Asia.

These fish possess a very unusual internal anatomy. In almost all other fish, the digestive tract follows a specific path. For most species, the gastrointestinal tract passes to the right of the stomach. In Osteoglossiformes, this is different. The forward part of their gut passes to the left of the oesophagus and stomach. This anatomical difference is a key way to identify them. It shows how much they vary from other ray-finned fish.

Scientists divide this group into different families and suborders. The two main sub-orders are the Osteoglossoidei and the Notopteroidei. One family is the Pantodontidae, which includes freshwater butterfly fishes. Another is the Osteoglossidae, known as the bonytongues. The Arapaimidae family contains the large arapaimas. The Notopteridae family includes featherfin knifefishes or featherbacks. Within this group, there are subfamilies like the Asiatic featherbacks. There are also the African knifefishes, known as Xenomystinae.

Some members of this order have developed amazing ways to sense their world. The Mormyridae family contains elephantfishes. The Gymnarchidae family includes the African knifefish, or *Gymnarchus niloticus*. These are known as weakly electric fish. They do not use electricity to shock others. Instead, they create electric fields to sense their prey. This allows them to find food in different environments. It is a specialized way to navigate and hunt.

The history of these fish is tied to the movement of the Earth. They first evolved on the supercontinent called Gondwana. This massive landmass eventually broke apart into smaller continents. This explains why they are found in disconnected places like Africa and South America. For a long time, people thought they were only freshwater fish. However, research in 2008 changed this view. Scientists described new marine species from the Danish Eocene Fur Formation. This discovery showed that the group is even more diverse than once thought.

The size range within Osteoglossiformes is truly massive. The smallest member is *Pollimyrus castelnaui*. This tiny fish is only 1 cm long. On the other end of the scale is the arapaima, or *Arapaima gigas*. This giant fish can grow to be as long as 3 meters. This shows how much the group has changed over time. They can be tiny or enormous, depending on their specific family.

Studying these fish helps scientists understand the history of life. They provide clues about how ancient continents like Gondwana were shaped. Their unique digestive systems show how biology can take different paths. Even the mooneyes, or Hiodontidae, are often linked to this group. Some scientists believe they might belong to a separate order called Hiodontiformes. Whether in freshwater or ancient marine fossils, these fish tell a complex story of evolution.