Does a Turtle Have a Backbone? (A-to-Z About Turtles’ Backbone)

Have a look at your pet turtle. What sets your pet friend apart from other animals? Their hard, bony shell. But where in the turtle’s body is the shell connected to? Does a turtle have a backbone? 

Well, yes, turtles do have backbones. Turtles belong to the vertebrate group of animals. It means they possess an internal skeleton that includes a backbone or spinal column. 

Interested to know more? Let’s explore the turtle backbone, from its purpose and integration with the shell to its length and bones. Find out how it compares to the backbones of other vertebrates and everything else! 

Do Turtles Have A Backbone? (Full Explanation)

As mentioned, the answer is YES – turtles have backbones. The turtle backbone is the anatomical feature that classifies them as vertebrates.

According to the Department of Education Open Textbook Pilot Project, vertebrates are animals that possess vertebrae – a backbone or spinal column. 

All turtles, from land tortoises to sea turtles, have backbones composed of vertebrae. Their backbones allow them to flex their necks, tails, and bodies for mobility and coordination. 

Turtles are the oldest living group of reptiles that have evolved to possess a specialized backbone over millions of years. This statement is backed by a 1998 study published by Nature. 

Is The Turtle Backbone Integrated Into Its Shell? How? The Physiology of Turtle’s Backbone

The turtle’s backbone is indeed integrated into the turtle’s shell. In fact, a 2013 study argues that the shell itself grows and forms in a turtle from its backbone.  

How the backbone stays connected to the shell is as follows. 

• The backbone runs through the “upper carapace” (top) portion of the shell.
• The vertebrae of the backbone connect to the inner part of the upper shell called the neural plates. (Note: Neural plates are large, flattened bones that form the central part of the shell’s top.)
• The vertebrae articulate directly with the neural plates. This essentially attaches the backbone securely within the top shell. 

This arrangement allows the shell to protect the backbone while still allowing flexibility. For example, when a turtle retracts its head into its shell, the vertebral attachment provides stability. 

Overall, the integration between the backbone and shell gives structural support for the turtle’s body. As it’s clear, the backbone is one of the core parts of a turtle’s anatomy and physiology. 

How Long Is A Turtle’s Backbone?

The backbone length ranges between 50% to 70% of the total body length for most turtles. In specific numbers, the backbone length can be anything between 2 inches to 5 feet, based on different species. 

Different turtle species have variations in their vertebral numbers and proportional backbone lengths compared to their bodies. 

Here are some examples:

• Sea turtles – Sea turtles tend to have the longest backbones proportional to their body length. An adult green sea turtle has about 150-200 vertebrae, with their backbone making up about 70% of the total body length.
• Terrestrial tortoises – Tortoises that live on land have shorter backbones with sturdier vertebrae. A Galapagos tortoise has around 60 vertebrae, making up around about 50% of its body size.
• Snapping turtles – These larger turtles have approximately 50-70 vertebrae, with backbones reaching about 50-55% of their total body length. 
• Musk/mud turtles – Smaller turtle species like these have backbones made up of roughly 25-35 vertebrae, comprising around 50% of their total body size.

How Many Bones Do Turtles Have In Their Backbone? Which Ones? 

The number of bones a turtle has in its backbone ranges between 20 to 60. These bones can be arranged in 5 regions: cervical (neck), thoracic (chest), lumbar (lower back), sacral (pelvis), and caudal (tail). 

Each region has a different number and shape of vertebrae that reflect its function and adaptation.

The following table summarizes some features of each region of the turtle’s backbone.

Notes: The upper surface of the turtle shell is the carapace, and the lower surface of the shell is the plastron. 

Region	Number of Vertebrae	Shape and Function of Vertebrae	Relation to Shell
Cervical	7 (8 in some sea turtles)	Small and flexible, allowing head and neck movement. The first vertebra (atlas) articulates with the skull. The second vertebra (axis) has a projection (odontoid process) that fits into a hole in the atlas, forming a pivot joint that allows head rotation.	No relation to the shell.
Thoracic	10-12 (9 or 13 in some sea turtles)	Large and rigid, forming part of the carapace. The vertebrae articulate with the ribs, which are also fused to the carapace. The ribs form a cage that protects the heart and lungs.	Fused to carapace and ribs.
Lumbar	2-4 (1 or 5 in some sea turtles)	Small and flexible, allowing some lower back movement. The vertebrae do not articulate with any ribs or shell bones.	No relation to the shell.
Sacral	1-2 (none or 3 in some sea turtles)	Large and fused together, forming part of the plastron. The vertebrae articulate with the ilium bones of the pelvis, which are also fused to the plastron.	Fused to plastron and ilium.
Caudal	Variable (none to over 30)	Small and flexible, forming part of the tail. The tail can be long or short, depending on the species and function. The vertebrae have projections (chevrons) on their underside that support the tail muscles.	No relation to the shell.

With so many functions being served by the components of the backbone, there remains no question of how vital the backbone is for turtles’ livelihood. 

You now know whether turtles can live without a shell or backbone. They CAN’T. 

Are Turtle’s Backbones Similar To The Backbones of Other Animals, Or Is It Fully Different?

The turtle backbone does share some key similarities with the spinal columns of other vertebrates, including mammals, birds, and reptiles.

Similarities:

• Composed of multiple vertebrae segmented into regions.
• Vertebrae articulate together and enclose/protect the spinal cord.
• Allows for flexion, extension, and lateral bending motions.
• Integrated with rib cage via dorsal vertebrae.

Differences:

• Turtle vertebrae fuse to the inner shell (neural plates).
• Shorter, stockier vertebrae compared to mammals.

• Varying number of vertebrae and proportional backbone size.
• Unique shape and size of turtle-specific vertebrae.

So, the overall construction is similar in terms of vertebral bones forming a flexible column. However, the turtle backbone does have unique adaptations specific to its shell integration and body form. 

Can a Turtle’s Backbone Fracture or Break?

A turtle’s backbone is integrated into its protective upper shell. So, it may seem unlikely that the backbone could become damaged. 

However, there are certain situations in which a turtle can suffer spinal fractures or breaks. The vertebrae provide flexibility for the turtle’s neck and body. But, traumatic impacts or continued stress can overwhelm the strength of the bones. 

Some potential causes of turtle backbone injuries include:

• Falls from heights – If a land turtle falls from an elevated surface and lands forcefully on its shell, the impact can cause fractures of the vertebrae or neural plates. 

The height of the fall and landing surface play a role in how severe the fracture might be.

• Dog/predator attacks – Dogs or predators that bite and shake a turtle forcefully can fracture vertebrae in the neck or lower shell. The powerful biting forces applied at angles can snap bones.
• Being struck by vehicles – Turtles that get hit by cars, boats, or other vehicles can suffer spinal trauma from the intense blunt force. Fast-moving objects can be hit with enough energy to break bones. 
• Difficulties in egg-laying – For gravid (pregnant) female turtles, difficulties in laying eggs can put tremendous strain on the backbone. 

Dystocia or egg-binding issues have been known to cause vertebral dislocations or separations.

• Diseases/nutritional deficits – Metabolic bone diseases from poor nutrition or diseases like shell infections can weaken and degrade vertebrae.

While not common, spinal trauma does occur in turtles and can be life-threatening if the spinal cord is damaged.

Conclusion:

In summary, yes – turtles certainly do have backbones! Their spinal column is composed of multiple vertebrae that integrate with the upper shell to provide flexibility and support.

Turtle vertebrae come in cervical, dorsal, lumbar, sacral, and caudal sections that allow neck, body, tail, and limb movements. While being similar in overall function to other vertebrates, the turtle backbone does have its own signature features that set it apart. 

So, are you not fascinated yet? Read more of our blogs to find out more such interesting turtle facts!