What’s Inside a Turtle Shell? [Turtle Anatomy]

Inside a Turtle Shell

Thanks to cartoons, many of us think of the turtle’s shell as more of a housing or case. However, the shell doesn’t house the turtle. Rather the shell is part of the turtle’s body and is made of bones, collagen, skin, and keratin.

The turtle doesn’t have a separate body within the shell. As such, the shell has nerve endings and can bleed when damaged.  Still, the question remains, ‘What’s inside a turtle shell?’

Table of Contents

1. Everything inside a turtle shell
2. The Anatomy of a Turtle Shell
3. The Carapace
4. Bony Plates of The Carapace
5. Scutes of The Carapace
6. The Plastron
7. Bony Plates of The Plastron
8. Scutes of The Plastron
9. Turtle Shell Facts and FAQs

Everything Inside the Shell

Located inside the shell are the turtle’s internal organs such as the heart and lungs. In addition to the reproductive organs, these are the organs found inside the shell:

• Esophagus: This is the passage from the mouth to the stomach
• Trachea: This is the airway/wind pine of the tortoise
• Lungs: The lungs are the two main respiratory organs
• Heart: The heart pumps blood through the body
• Stomach: This is part of the digestive tract and is located between the esophagus and the intestines
• Intestine: This digestive tract organ comes after the stomach
• Pancreas: This organ is responsible for producing digestive enzymes
• Liver: The liver produces bile
• Bladder:  The bladder stores urine
• Rectum: This is the final part of the digestive tract
• Anus: This is the digestive tract’s outlet

So the answer to the question, ‘Can a turtle survive without its shell?’, is no. Without a shell, the guts, heart, lungs, and all will spill out.

The Anatomy of a Turtle Shell

The shell is made of two parts, or three if you count the bridge as a separate entity. These include –

• The carapace: The upper part of the shell. This forms the dome of the turtle.
• The plastron: The lower part of the shell, which covers the underside of the turtle.
• The bridge: This connects the carapace and the plastron. The bridge is part of the plastron.

Scutes, which forms the outermost layer of the shell, are made of keratin – the same material that makes up human nails. As such, the scutes are flexible and tough.

The scutes protect the bony shell from damage. As the land tortoise grows, so does the scutes, with new rings being added. One way of calculating a tortoise’s age is by counting the scute rings.

Aquatic turtles shed old scutes. As the turtle sheds, it looks like the turtle shell is peeling off. Not all turtles have scutes. Some have skin over the shell. These include the freshwater softshell turtles and the leatherback sea turtles.

The Carapace

The carapace is the dome on the turtles back. This convex part of the shell is made up of ossified rib bones fused with the dermal bone. Both the ribs and the backbone are fused to the dermal plates through the process of ossification.

On top of this is skin. This skin is then covered with scutes – which as you know is made of keratin. The scutes protect the bony plates from bruises, cuts, and scrapes.

Some turtles such as map turtles and several sea turtles have a keel that goes down the shell. Keels are generally present on the shells of aquatic turtles.

Several bones make up the turtle’s shell including the neural plates, peripheral plates, the pleural plates, proneural plates, pygal plates, and suprapygal plates.

On top of these bony plates are the scutes also known as epidermal laminae. The scutes are easier to see and as such plays an important role when it comes to turtle identification.

The scutes can be divided into the coastals (lateral scutes), marginal scutes, and vertebrals (central scutes and precentral scutes).

Bony Plates of The Carapace

These come together to form the skeleton of the carapace.

• Proneural plate:  This bone is found at the center front position of the shell nearest to the head. Every turtle has a single proneural plate in its shell.
• Neural plates:  These come right after the proneural plate and are located at the front of the shell. They go down the midsection of the shell towards the tail. Most turtles have about 8 neural plates.
• Suprapygal plates:  These bones (usually two of them) are located right after the neural plates at the end of the shell.
• Pygal plate:  This is at the tail end of the shell. Every turtle shell has a single pygal plate.
• Pleural plates: On either side of the neural plates, you can find the pleural plates. They are broad and long. Most turtles have about 16 pleural plates.
• Peripheral plates – Peripheral plates are located along the edge/peripheral of the carapace. Some turtles can have as many as 22 peripheral plates. The first peripheral bone connects to the proneural plate and the pleural plate closest to the proneural plate. The peripheral plates then go round the edge until they connect to the pygal plate. This happens on both sides of the shell. 

These bony plates all together form the carapace.

Scutes of The Carapace

On top of the bony plates are the scutes. The scutes are the visible part of the shell. Most turtles have 11  to 13 main scutes. These 11 to 13 scutes are easy to count and can be used in identifying the turtle. However, around the edge of the carapace, there are several (about 24) small scutes known as marginal scutes. They are called marginal scutes as they are located along the margins of the carapace.

• Nuchal scute: This is the scute directly behind the turtle’s head.
• Central scutes: The central scute is right in the center of the shell. It is usually the topmost shell. There is usually a single central scute.
• Precentral scutes: These are located next to the central scute. There are usually 4 precentral scutes, arranged medially. The central and precentral scutes are collectively known as the vertebral.
• Lateral scutes: These scutes are located on both sides of the central and precentral scutes. There are usually about 8 lateral scutes, 4 on each side of the vertebral. The lateral scutes are also known as coastals.
• Marginal scutes: These are tiny scutes can be found along the edge/margin of the carapace.

Most turtles have about 13 scutes, not counting the many marginal scutes.

The Plastron

This is the flat part of the shell located at the underside of the turtle. The plastron also includes both the posterior and anterior bridge struts as well as the bridge. The plastron is composed of about nine bones including two epiplastra (plural of epiplastron).

Bony Plates of The Plastron

Epiplastron: Each turtle has two epiplastra. These are located at the front of the plastron. The left and right epiplastra are located side by side.

Entoplastron: Right underneath the epiplastra is the entoplastron. This bone shares borders with the two epiplastra and two hyoplastra right underneath the epiplastra.

Hyoplastron: Two hyoplastra are located underneath the epiplastra on both sides. Two more hyoplastra are located underneath. In all, there are 4 hyoplastra.

Xiphiplastron: Underneath the hyoplastra, are two xiphiplastra.

Bridge: The bridge connects the plastron to the carapace.

Scutes of The Plastron

Just as with the carapace, scutes are found atop the bony plates. The plastron has 6 different types of plastron scutes. These include the gular, humeral, pectoral, abdominal, femoral and anal.

Gular scutes: This pair of scutes is situated directly behind the turtle’s head. 

Humeral, Pectoral, Abdominal, and Femoral scutes: A pair of humeral scutes directly follows the gular scutes, followed by a pair of pectoral scutes, followed by a pair of abdominal scutes and finally a pair of femoral scutes. Some turtles such as the musk turtles have triangular pectoral scutes while others such as mud turtles have squarish pectoral scutes.

Anal scutes: The last pair of scutes are referred to as anal scutes.

Turtle Shell Facts and FAQs

The turtle shell is a fascinating and interesting enigma, one that has perplexed everyone including biologists for ages. Today, we understand the turtle shell better. Here are some turtle facts and FAQs.

1.  Can a turtle live without its shell?

Sadly, the answer is no. The shell includes the turtle’s backbone, and ribs. Since it is a part of its body, the turtle cannot live without the shell.

2. What does a turtle look like without a shell?

A turtle without its shell is a dead turtle. There is currently no turtle without a shell. Since no turtle species exist without shells, we would never know how a shell-less turtle looks like.

3. Can a turtle survive without its shell?

While the turtle cannot survive without its shell, it can survive a lot of damage to the shell. Turtles can live with extensive shell damage. Turtles can also heal damages done to the shell such as cuts, bites, cracks and may more. If your turtle is injured, treat the injury with a Betadine©  solution and seek professional help from a herp vet.

4. What color is a turtle shell?

Turtle shells come in many different colors. However, common shell colorations include olive-green, tan, brown and black. For example, turtles species such as the sliders have olive-green or brown carapaces. The plastron is usually lightly colored. For example, the yellow-bellied slider has a yellow plastron, while the red-bellied cooter has a reddish plastron. The ever-popular map turtles generally have greenish to brownish looking shells with yellow marking. Most tortoises have brown shells.

5. How hard is a turtle shell?

Shells are very durable and protect the turtle from harm. However, they may not be as hard as you think. Softshell turtles actually have leathery shells, which are soft to the touch. However, there are very few softshell turtle species. Even turtles with hard shells (literally every other turtle but softshell turtles and leatherback sea turtles) have a soft and protective layer of scutes and collagen.

6. How strong is a turtle shell?

Not only is a turtle shell incredibly strong, but it also protects the turtle from all sorts of harm. The shell is composed of bone plates covered with collagen, and scutes. These act as shock absorbers, helping to protect the bony plates underneath. Regardless of this, turtle shells can be damaged by animals such as dogs and cats. Ensure your pet turtle is safe from dogs and cats. Dogs are especially prone to attacking turtles and can easily harm or even kill them. Cats can also cause irreversible damages to small and medium-sized turtles.

7. Does a turtle shell grow?

As with any body organ, the shell grows with the turtle. The bones get bigger, and so does the scutes. Scutes of aquatic turtles are shed when the turtle outgrows them. These are replaced by new scutes. For tortoises, rings are added to the scutes as the turtle grows bigger.

8. Is a turtle’s shell part of its body?

The turtle shell is a part of the turtle’s body and not an object it carries around. Both the backbone and ribs are part of the shell.

9. Can turtle shell bleed?

With enough damage, a turtle shell will bleed like any body part. However, the shell is much stronger and can withstand more force than other body parts such as the limbs, tail, and head can. As slow creatures, they find it difficult escaping harm.

10. What is a turtle shell called?

There is no special scientific name for the turtle shell. The shell of the turtle is simply referred to as ‘the turtle shell’. This shell is made up of the carapace, plastron, and bridge.

Conclusion

If you enjoyed reading the above we created a gorgeous infographic which we definitely would love for you to see.

Check out the Turtle Shell Infographic Here!

Different species of turtles and tortoises have shells with different shapes, colors, sizes and even feels. The shells which are part of their body protect them against the weather and predators.

Aquatic turtles even utilize the shell when hunting. If you have a pet turtle or tortoise, their diet must be well supplemented to avoid shell problems such as pyramiding, which can kill the turtle.

Additionally, ensure any shell injuries are treated as soon as possible. If you have any comments, corrections, or suggestions, we would love to hear them in the comment section below.

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