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9 Ways Reptiles Are Similar To Mammals

We all know that reptiles and mammals are very different. It is a well-known fact that reptiles and mammals are very dissimilar, and they have very contrasting characteristics. However, there are some who may be wondering if there are any significant similarities between reptiles and mammals?

There are several significant similarities between reptiles and mammals, including respiratory systems, circulatory systems, skeletons, sexual dimorphism, nervous systems, and the fact that they are both tetrapods. Reptiles and mammals have many differences, but there are many similarities as well.

While reptiles and mammals are clearly very different, and there are so many differences between them that it is very hard to imagine that they have any similarities at all, but the truth is that reptiles and mammals are similar in many ways. Let’s explore some of the significant similarities between reptiles and mammals.

Are There Really Similarities Between Reptiles And Mammals?

It is a well-known fact that reptiles and mammals are very different, and it is clear that they do not have that much in common, right?

The truth is, reptiles and mammals have a lot in common.

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We think of reptiles as scaley, strange creatures like snakes and lizards, while mammals are generally thought of as fury and sometimes cute animals such as dogs and bears.

While this is true, mammals are usually fury animals, and reptiles often have smooth scales; there is much more to these two types of creatures than just their appearance, as there is much more complexity to reptiles and mammals than meets the eye.

There are very broad similarities between reptiles and mammals, such as the fact that most of them have eyes, they all have systems of muscles that allow them to move about on land or in water, they all have mouths, and most have teeth and tongues, and they both often inhabit very similar habitats.

These are the very obvious similarities between these two types of animals, but there is much more to notice if you look closer.

Reptiles and mammals have more in common than you may realize. Both reptiles and mammals are Chordates due to their dorsal neural tube that develops into a spinal cord.

Reptiles are cold blooded (ectothermic), and mammals are warm blooded (homeothermic), but they both have closed circulatory systems with a heart.

Both reptiles and mammals digest food with a stomach, they both have skin, they both reproduce sexually, they both have excretory systems that include bladders and kidneys, and they are both amniotes meaning that they either lay eggs on land or retain fertilized eggs within the mother.

These are very broad similarities, but there are similarities nonetheless.

The similarities between reptiles and mammals go even deeper if you are willing to search them out.

Let us take a much deeper dive into the similarities between these two truly fascinating animal types!

Check out my article here to discover why reptiles are really called reptiles!

9 Ways Reptiles Are Similar To Mammals

There is much to reptiles and mammals than meets the eyes, and they have much more in common than the obvious similarities we have looked at already.

There are many ways that reptiles are similar to mammals, and some of them may not be what you expect.

Below are some of the significant ways that reptiles are similar to mammals:

1. Tetrapods

Both reptiles and mammals are Tetrapods.

Tetrapods are a class of animals that belong to the superclass Tetrapoda, which means they are four-limbed vertebrates.

All reptiles and all mammals are vertebrates, meaning that they have a spine, and they are all four-legged animals by definition.

Even snakes are classified as tetrapods, even though they do not have four external limbs or any limbs at all, they did have limbs at some point in their history, and they are similar enough to other reptiles to be grouped in the same class of tetrapods as all reptiles.

Tetrapods have much more in common than simply a spine and four limbs, but the broad definition of Tetrapods include how their skull and jaw is defined and used, how they feed and digest food materials, they breathe with lungs and expel carbon dioxide, they can all see and hear, and they all have circulatory systems with a heart.

While this classification does include many species and animal types, reptiles and mammals are the biggest members of the Tetrapod family, and they have all of the same characteristics in this regard.

2. Respiratory System

Mammals and reptiles share very similar respiratory systems

Reptiles and mammals have a very similar respiratory system.

They both make use of lungs to extract oxygen from the air around them, and the oxygen is transported via blood vessels from the lungs to the rest of the body in their blood.

The respiratory system of both reptiles and mammals includes a pharynx, which is part of the top throat that is found behind the mouth and nasal cavity.

The pharynx is the tubes that lead from the mouth and nasal cavity in both reptiles and mammals that allow for breathing and for swallowing food, both processes being performed in the same location but leading to different places in the body.

Reptiles and mammals share very similar respiratory systems, and the functions of these systems are exactly the same in both types of animals.

3. Bilateral Symmetry

Bilateral symmetry refers to the layout and shape of the body of an animal.

Animals that are bilaterally symmetrical have evenly laid out bodies, with body parts that are equally distributed in each area.

Bilaterally symmetrical animals have a top (dorsal) side, bottom (ventral) side, head (anterior) side, tail (posterior) side, and very distinct left and right sides divided by the Sagittal plane.

All of the limbs and extremities of the bilaterally symmetrical animals are evenly distributed, but not all of their internal organs and mechanisms are necessarily evenly distributed.

Reptiles and mammals have a spine that supports their endoskeletal system, and all of their limbs are equal on each side and in each quarter of their bodies.

They have a head and a tailor tail area, their bones are symmetrical, and their bodies are evenly proportioned, with each feature of the body on either side of the Sagittal plane being very similar to each other and similarly proportioned.

4. Digestion And Excretion

Reptiles and mammals share very similar digestion and extraction systems.

Both animal types take in food and liquids through their mouths, which is then digested by a complex digestion system that always includes intestines, stomachs with stomach secretions that aid in digestion, livers, kidneys, and bladders.

Retiles have a much slower digestive system than most mammals due to a significantly slower metabolism, but the digestive system of both animal types works in the same way.

The same is true for how both reptiles and mammals deal with and excrete waste.

Reptiles and mammals both extreme waste products from food and liquids the same way. Most reptiles have one organ that all waste material is excreted from, the cloaca, but this is merely where the waste product exits the body.

The same organs deliver the waste materials to the cloaca as do in mammals, and so both reptiles and mammals have surprisingly similar digestive systems and excretion methods compared to other animal types.

5. Central Nervous System

The central nervous system is another similarity between reptiles and mammals and is one of the most important commonalities between these two animal types.

Both reptiles and mammals have a brain, and a spinal cord that makes up the majority of their nervous system, with outlying nerves throughout the body that all send signals via the spinal cord to the brain to control the movements and functions of the body.

The brain of both reptiles and mammals is contained within the skull, and the spinal cord is contained within and protected by the vertebrae of the spine of both animal types.

This is an important feature that reptiles have in common with mammals, as this is the main means of how the brain controls the body and how the body grows, protects itself, and how the animal thinks and makes decisions.

It may seem like a trivial similarity, but it is amazing how the incredibly complex neurological systems of both reptiles and mammals, animal types that are distinctly different, are both so similar in their function, composition, and layout.

6. Circulatory System

Mammals and reptiles use the same circulatory systems in their bodies

The circulatory system is something that is also common between reptiles and mammals.

Mammals are homeothermic (warm blooded), and reptiles are ectothermic (cold blooded).

The homeothermic nature of mammals means that they are able to internally self-regulate their body temperature, which allows their body temperature to remain somewhat constant regardless of their external environment.

Reptiles are ectothermic, which means that their bodies are not able to regulate their own internal temperature effectively, meaning that their body temperature is determined by their external environment, and they need to use external sources to regulate their body temperature.

However, despite the fact that reptiles are cold blooded and mammals are warm blooded, they both have a similar circulatory system.

The circulatory systems of both reptiles and mammals are cardiovascular, which means that they both have a heart that pumps blood through the entire circulatory system.

Reptiles and mammals both have multi-chambered hearts, arteries, veins, and other important blood vessels that transport and distribute blood and nutrients throughout the body.

The circulatory systems of reptiles and mammals incredibly similar. There are some significant differences in the make-up reptile vs. mammal hearts and their ability to thermoregulate, but the systems themselves are almost identical and function in the same way and for the same reasons.

7. Endoskeletal System

Reptiles and mammals both have complex endoskeletal systems.

This means that their skeletons are made from bone and cartilage, and they are entirely inside the body of the animal.

This is always true for every species of mammal and reptile.

The fact that both of these animal types have endoskeletons means that they share a few more things in common as well.

They both have spines, which makes them vertebrates, they both have rib cages to protect their lungs and other vital organs, they both have muscles, ligaments, and tendons that enable them to move, and their skeletons provide both animal types with the physical and structure required to conduct various necessary activities.

The bones and skeletal composition of reptiles and mammals are very similar and function for the same purposes.

8. Vertebrates

Due to their similar endoskeletal system, both reptiles and mammals are vertebrates.

Reptiles and mammals are both animals that fall into the category of Vertebrates because they are both Chordates with a backbone.

This is the definition of a vertebrate. Reptiles and mammals both have a spine made up of segmented joints with are the vertebrae.

This spine forms the main connecting element of the dorsal and vertical sides of the endoskeleton and contains and protects the spinal cord, which is vital for both animal types.

The spine of reptiles and mammals are both remarkably similar in layout, function, and composition.

Reptiles and mammals both have a notochord that develops into the vertebral column when the animal matures. This is what defines both animal types as Chordates.

This is a vital aspect of the anatomy of both reptiles and mammals and is a very significant and defining similarity between the two animal types.

9. Sexual Dimorphism

Reptiles and mammals are both known to be sexually dimorphic.

This means that the male and female of a species have different characteristics apart from their reproductive organs.

The male and female have different characteristics

Sexual dimorphism can take place in different ways across all sexually dimorphic species of reptiles and mammals, but many of these two animal types exhibit the same types of sexual dimorphism.

Many species of reptiles grow larger or smaller depending on their gender, and the same is true for many mammalian species as well.

Reptillian males and females often have different colorations and grow different-sized appendages such as tails and heads. Mammals often display the same traits, and male and female mammals from almost every species look very different and grow to different sizes.

The degree of sexual dimorphism in both reptilian and mammalian species varies drastically, but this is a characteristic that both animal types almost always exhibit.


Reptiles are amazing creatures, and there is so much more to them than their scaly and strange appearance.

Mammals are often fury and can be seen as cute, and many of them are large and terrifying, but they have their own unique features and characteristics as well, having much more to them just the way they look.

By looking at these two animal types, it is hard to imagine that they have so much in common, but they really do.

Reptiles and mammals may not appear to have many similarities, but there is much more that they have in common than meets the eye.

Apart from the very obvious characteristics of reptiles and mammals, such as their eyes, their mouths, and the fact that they have tongues, there are many ways that reptiles and mammals are similar.

Some of the significant similarities between reptiles and mammals include their broad animal classification, their skeletal structure, composition, and vertebrae, the way their central nervous systems and circulatory systems work and are composed, the fact every reptile and mammal have proportionate bilaterally symmetrical bodies and are sexually dimorphic.

Reptiles and mammals are both amazing anima types, and they both have amazing and distinctive features and characteristics, but they have a surprising number of features in common.

The next time you see a reptile, consider all of these features and remember that they have more in common with mammals, including you than meets the eye!

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