Tetraodontiformes

Some fish have very strange shapes.

They can be round like a ball. Others are shaped like a box.

These fish live in oceans all over the world. Some even live in fresh water. Many have hard plates or spines to stay safe.

Some fish can even puff up with water. This helps them look much bigger. They use their fins to move through the sea. These fish are truly amazing to see!

Some fish have very strange shapes.

They do not look like most fish. Some are round like a ball. Others are shaped like a box.

These fish are called Tetraodontiformes. This name means "four teeth" in Greek. This is because their jaw bones fuse into a beak. These bones look like teeth.

Most of these fish live in the ocean. Some live in fresh water. They are found all over the world. They use different ways to stay safe. Some have hard plates or sharp spines.

Pufferfishes can puff up to look big. They do this by sucking water into their stomachs. Many pufferfishes also use a poison called tetrodotoxin. This toxin is kept in their organs.

The ocean sunfish is the largest of them all. It can grow up to 3 meters long. It can also weigh over 2 tonnes!

Most of these fish are slow swimmers. Their bodies are very stiff. They use their fins to move and steer. They eat things like shellfish and jellyfish.

Some fish look very different from the ones you see in a typical aquarium.

These fish belong to a group called Tetraodontiformes. This name comes from Ancient Greek words meaning "four teeth" and Latin meaning "form." Most of these 430 species live in the salty ocean. However, a few can be found in fresh water too. They live in waters all around the world. They are famous for having strange body shapes that are not streamlined like most fish.

These fish use many clever ways to stay safe from predators. Instead of swimming fast, they rely on being tough. Many have scales that have turned into hard plates or sharp spines.

Some, like the pufferfish, can swallow water into a part of their stomach to puff up. This makes them much larger and harder to eat. Others have thick, leathery skin to protect them.

Some species even use a powerful poison called tetrodotoxin. This toxin is kept inside their organs to keep them safe.

Scientists have been studying these fish for a long time. In 1817, the group was first called the Plectognathi. Later, in 1940, a scientist named Lev Berg used the name Tetraodontiformes. This name follows special rules for naming animal groups. It is based on a specific type of fish called Tetraodon lineatus. This fish was first named by Linnaeus in 1758. Today, experts use these names to help organize all the different types of fish.

There are many different sizes and families in this group. The smallest is a filefish called Rudarius excelsus. The largest is the ocean sunfish, which is a huge bony fish.

It can grow up to 3 meters long and weigh over 2 tonnes. Most of these fish have very stiff bodies. They cannot bend their bodies to swim like other fish do. Instead, they use their fins to move and steer through the water. This makes their movement very precise even if they are slow.

Their mouths are also very special for eating. Most of these fish like to eat hard-shelled creatures like shellfish.

To do this, their jaw bones have fused together into a shape like a beak. These beak bones are divided by lines that look like teeth. Scientists can count these "teeth" to tell different families apart. For example, some have two teeth-like bones and others have four. This helps us understand how these unique fish are related to one another.

The Tetraodontiformes are a diverse order of ray-finned fishes. This group includes well-known animals like pufferfishes and boxfishes. They are famous for having body shapes that look nothing like typical, streamlined fish.

While most species live in the salty ocean, some live in freshwater. There are about 430 known species spread across 10 different families. They are found in waters all around the world. This group is a highly specialized lineage of fish.

Most Tetraodontiformes use a strategy of defense instead of speed. Many species have scales that have evolved into hard plates or sharp spines.

Others, like filefishes and the ocean sunfish, have tough, leathery skin. Pufferfishes have a very unique way to protect themselves. They can inflate their bodies to increase their diameter. They do this by sucking water into a diverticulum, which is a pouch in their stomach.

Some species, including many in the Tetraodontidae family, also use a neurotoxin called tetrodotoxin. This powerful chemical is concentrated in their internal organs to stop predators.

These fishes have highly modified skeletons that differ from most other fish. They lack several bones, such as the nasal, parietal, and infraorbital bones. They also usually lack lower rib bones. Their jaws are modified and fused into a structure that acts like a beak.

This beak is divided by visible lines called sutures that look like teeth. Scientists use these "teeth" to distinguish between different families. For example, the Tetraodontidae are "four-toothed" and the Diodontidae are "two-toothed." Because they eat hard-shelled prey like crustaceans, they use powerful muscles to operate these jaws. Many also have pharyngeal teeth to help process their food.

Body shape and movement vary greatly within this order. Some fish, like boxfishes, are nearly square or triangular. Others are globose, which means they are round like a ball. Filefishes and triggerfishes are laterally compressed, meaning they are flattened from side to side.

Most members are ostraciiform swimmers. This means their bodies are rigid and cannot bend sideways. Because they cannot undulate their bodies, they are relatively slow movers. They rely on their pectoral, dorsal, anal, and caudal fins for propulsion. This allows them to be very precise when maneuvering.

The size range in this order is truly massive. The smallest member is a filefish called Rudarius excelsus, which is only a few centimeters long. In contrast, the ocean sunfish is the largest bony fish in the world.

An ocean sunfish can reach lengths of up to 3 meters. They can also weigh more than 2 tonnes. The ocean sunfish is very different from its relatives. It lacks a swim bladder and spines. It also lacks a caudal peduncle, which is the part of the body before the tail. Instead, its tail is a stiff, rudder-like structure used for steering.

Taxonomy, or the science of naming and grouping, has changed for this order over time. In 1817, the group was proposed as the Plectognathi. Later, in 1940, Lev Berg introduced the name Tetraodontiformes. This name is based on the type species, Tetraodon lineatus, which was named by Linnaeus in 1758. The name comes from Ancient Greek words for "four" and "tooth" and the Latin word for "form."

Recent studies have changed how scientists classify them. While once considered a suborder of Perciformes, they may actually be a sister taxon to the anglerfish order, Lophiiformes.

Fossil evidence helps us understand the history of these fish. The oldest recognized ancestors are the extinct Plectocretacicoidei from the Late Cretaceous period. These were found in the former Tethyan region, including modern-day Italy and Slovenia.

However, some scientists question if these fossils truly belong to this order. They note that these ancient fossils have traits not seen in modern Tetraodontiformes. If these are excluded, the earliest definitive fossils appear in the Eocene epoch. This history shows how much these fish have changed and specialized over millions of years.