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Are Fish Reptiles? Yes or No!

Do you often wonder, are fish reptiles? Well, owing to the striking similarities between fish and reptiles, it’s obvious to come up with this thought.

Though all fish and most reptiles prefer to stay in the water and are cold-blooded by nature, their behavior has certain striking differences.

Are fish reptiles? The quick answer is “No”. Fish are vertebrates having a more boney and scaly structure. They possess a two-chambered heart and gills, which help them thrive and live underwater. On the contrary, reptiles are also vertebrates, but they possess lungs and a three-chambered heart.

Are Fish Reptiles? The Detailed Explanation!

Well, no, fish are not reptiles; instead, they are a different class of vertebrates. However, they do have certain similarities with reptiles.

But what makes them have such similarities?

Fish are the foremost and common ancestors of all amphibians, reptiles, and mammals.

The origin of fish dates back to 500 million years ago.

On the contrary, reptiles made their first appearance in the world almost 200 million years after fish.

Amphibians emerged somewhere in between.


Which trait makes fish and reptiles similar enough? It’s cold-bloodedness. Most reptiles and fish are cold-blooded, which means these creatures cannot regulate their internal body heat with the changing temperature of their environment.

Fish’s body temperature tends to get adjusted as per their surrounding environment. Hence, instead of being called only cold-blooded, they are known to be poikilothermic.

But almost all reptiles are cold-blooded, not poikilothermic. Also, they are incapable of breathing underwater, unlike fish. It becomes too hard for reptiles to move during the wintertime.

Besides, both of them mostly have a scaly skin type. Also, their reproduction takes place through the production of eggs.

However, there are always exceptions in both cases.

Main Differences

The differences between these two types of animals are more significant. Here is a list of the main differences between fish and reptiles:

Way of Breathing

A fish distinguishes itself from reptiles with its possession of gills. Fish use their gills for breathing underwater. The water passes through their gill, which helps them to extract oxygen for their living.

Reptiles, on the other hand, do not have gills. Instead, they have lungs like us. Their ribs can expand and contract.

It allows their lungs to have more capacity than amphibians. Reptiles can be found in ponds or other water bodies sometimes. But they are not capable of breathing under the water.

Group of Origin

Fish and reptiles do not share the same group of origin. Fish are members of the Gnathostomata class.

They belong to the subphylum group of Vertebrata and a superclass of Chordata. These vertebrates have a structured jaw, and they live in water.

Reptiles, on the other hand, belong to the Reptilian class. The class includes many species like snakes, turtles, lizards, etc.

They possess an epidermal gland.

Heart Structure

Fish do possess hearts. But their hearts are in many ways different from the hearts of reptiles. Fish have a two-chambered heart.

Reptiles have a three-chambered heart. It contains auricles and partially divided ventricles.

However, it can differ from one species to another one.


When it comes to limbs, fish do not have many prominent ones. They have a more shallow and flattened structure, which helps them navigate through the water.

Reptiles have improved limbs. Their limbs are also known as pentadactyl limbs, which help them to crawl and burrow the ground.

Skin structure

Reptiles have scaly skin. They usually differ from each other. Their skin is also very dry, watertight, and rough.

Fish have a more scaly and bony structure on their skin. Also, some fish species lack scales.

Frequently Asked Questions

Is a goldfish a vertebrate?

Yes, the goldfish is a vertebrate. It is a domesticated cyprinid.

Goldfish tend to have close relations with the Crucian carp. Hence, they share a modern genome duplication that took place at least 8-14 million years ago. It stands to be one of the latest whole-genome duplications in vertebrates.

Is an eel a reptile?

It often comes to our minds that an eel must be a reptile, as its shape is more like a snake. But is it so? No, the eel is a fish.

They are more like a teleost. They do have bones and ray fins. But the embryo of an eel does not have any amniotic sac.

What makes it not a reptile is its absence of lungs. They respire aerated water through their gills, which stay covered within their bone-based scales. Hence, there is no doubt that the eel is not a reptile.

Is a starfish a reptile?

Though starfish have the term “fish” in their name, they are not fish. Then, what species are they? Reptiles? No! They are not at all reptiles, nor are they amphibians.

Starfish are echinoderm. “Echino” means “prickly” and “spiny.” On the other hand, “derm” means skin. Hence, starfish are a part of the phylum Echinodermata, which makes them have more spiny skin.

Is a jellyfish a reptile?

Jellyfish are neither fish nor reptiles. Jellyfish are jelly-like creature that thrives in the ocean. They are also not vertebrates either. Jellyfish do not have any backbone; hence, they are invertebrates.

Is a turtle a reptile or a fish?

A turtle does not look like other prominent, well-known reptiles like snakes, crocodiles, or lizards. But turtles are reptiles having an added shell over their body.

Similar to any other reptile, turtles also have rough skin and cold blood.

Since they have lungs to breathe, they are incapable of breathing underwater for a long time.


So, now have you got the answer to your question, are fish reptiles? Undoubtedly, they are not.

Even though fish are close ancestors of reptiles and share some similarities, they cannot be tagged as reptiles.

Fish belong to a different vertebrate group, which makes their anatomy and physiology quite dissimilar to reptiles.