Do Frogs Have Bones?

Frogs are amphibians and it may be confusing to know if frogs have bones since they are cute squishy-looking creatures. Well, I hated our high-school frog anatomy class because I love frogs and do not want to dissect them, but I did learn a few things.

Frogs are amphibians that have a skeleton and a backbone and are therefore tetrapod vertebrate animals. Although all amphibians possess a musculoskeletal system, their bones are very different from those of mammals being lightweight and structurally dissimilar.

If you are curious about frog bones and want to learn more, read on. We will discuss the difference between vertebrates and invertebrates, the unique features of a frog’s skeleton, and how it compares to humans.

Frogs Are Vertebrates

Frogs are vertebrates because they have a backbone and internal skeleton. Their lightweight bones give their bodies a structure while also allowing them flexibility for hopping, jumping, swimming, digging, crawling, or climbing depending on the species.

The animal kingdom is divided into two groups, vertebrates, and invertebrates. Vertebrates are animals with a backbone and an internal skeleton system, like mammals and birds. Invertebrates do not have internal bones. Rather, they have an exoskeleton on the outside of their body that protects their internal organs. Insects are invertebrates.

The word vertebrate refers to the vertebral column or backbone. Though the earliest vertebrates did not have backbones as we know them today, they have since become the defining features of the animal group. Other distinguishing features of vertebrates include a central nervous system and a muscular system.

What Bones Do Frogs Have?

The skeletal structure of a frog is relatively similar to many other mammals and even humans. They have many similar organs, such as the stomach, heart, liver, gallbladder, pancreas, lungs, and much more. As a result, frogs would need similar bones to protect these organs. 

Body PartFrog Bones
Head Skull, pterygoid, maxillary, orbital cavities, quadratojugal
Extremities Radio-ulna, humerus, tibiofibular, femur, tarsus, metatarsus, phalanges, carpus, metacarpus, phalange, calcanium, talus
Abdomen Scapular, prootic, occipital lateral, vertebrae, sacral vertebrae, urostyle, illium, ischium

Frogs Have a Skull And Legs

Frogs have a few bones in their heads, which forms the base for frog-like facial features. These bones protect the brain, eyes, tongue, and other crucial body parts or organs inside the head. Frogs also have very small teeth in their upper jaw. The skull is mostly bone by the time frogs reach maturity, but it will still contain some cartilage where necessary.

Frogs also have extremities from their four legs. Unlike humans, who have two bones at the end of the extremity running parallel to each other, frogs have extremity bones that are fused into one single bone furthest from the torso. The bones inside the extremities include two sections:

  • A bone that is closest to the torso with an elbow-type joint
  • A bone further from the torso which forms part of the extremity

Aquatic frogs typically have longer hind legs that are beneficial for jumping and shorter front legs for maintaining balance. The adaptations in leg length are also useful for swimming and replace the functionality of the tail that frogs would have had as tadpoles. 

Frogs Have Toes And Fingers

Its common knowledge that frogs have undeniably special feet, capable of various maneuvers, leaps, and miraculous gravity-defying stunts. The bones in their fingers and toes, otherwise known as digits, have a lot to do with their abilities. Frogs have five digits at the end of their hind legs and four digits at the end of their front legs. 

Most frogs have fairly long digits, making them incredibly useful in daily life. Arboreal frog species usually have flexible digits for climbing and jumping, while aquatic frog species usually have digits that support webbing for easy swimming. Most terrestrial frog species have shorter and wider feet with fairly robust digits, as they use their feet for digging and shoveling soil.

Frogs Have an Abdomen

The abdomen of frogs is fairly complex, with many small design details that drastically impact their overall ability and mobility in the wild. 

  • Backbones: Frogs’ backbones comprise a series of 10 bones that run from the brain along the back, protected from potential damage by a series of fused vertebrae or backbones. The series of bones along frogs’ backs also provides increased movement, which gives frogs an advantage over less-evolved vertebrate species and invertebrates.
  • Rib Bones: Upon first glance, the rib cage of a frog can appear to be similar to that of humans, but the nature of its design is very different. Humans have a set of ribs that are attached to the spine through cartilage tissue. On the other hand, frogs have ribs that are, in fact, horizontal bones that run across the torso, making them an integral part of the spine. 
  • Pelvic Bones: The pelvis of a frog is very unique, as it can slide up and down along the frog’s spine. The pelvic bones behave like an organic spring, allowing frogs to utilize momentum in their movements. This movement and skeletal design are responsible for frogs’ ability to jump high and leap great distances. 

But frogs are not born with bones like many other animals, as a frog’s life cycle starts inside an egg. They transform into tadpoles around 25 days after they are laid in water depending on the species. Yet, even as tadpoles. frogs do not yet have bones.

When Do Frogs Develop Bones?

Frogs remain fully aquatic for the first 6 to 12 weeks of their development, have no bones, and breathe through gills as young tadpoles. They are omnivores and feed on nearby vegetation with their tiny mouths. After approximately 14 to 12 weeks, tadpoles begin to develop small bones.

Most of the cartilage in their heads begins to turn into bone, and they begin growing hind and front legs. Throughout this phase of development, other changes also occur to make room for frog organ and muscle development, such as the development of strong tongue muscles. 

Frog Development PhaseBonesAverage Metamorphosis Time
Frog EggNone0 to 3 Days
Young TadpoleCartilage 1 to 6 weeks
Mature TadpoleMost Bones6 to 12 weeks
FrogletAll Bones2 to 4 years

Once the tadpoles grow their limbs and their skulls comprise bone and cartilage, they start to develop frog-like facial features. They begin transitioning to land and are then referred to as froglets (otherwise known as juvenile frogs) as they resemble miniature forms of adult frogs. 

A picture I took of a mature tadpole

By this point, the froglets would have developed ribs, limb bones, predominantly boney skulls, backbones, and many other smaller bones for proper functionality on land and in water. 

Cartilage Helps Frogs Be Flexible 

As vertebrates, we know that frogs have bones, including a backbone and other skeletal features such as skull and leg bones. However, just like other animals, including humans, frogs also have cartilage. 

A frog’s rear legs are made up of both bone and cartilage. The main structure of the leg is bone but the kneecaps are made of dense cartilage (Abdala, 2017). Frogs do a lot of jumping and landing and the cartilage in the kneecaps allows the legs to absorb the shock of jumping and landing, especially on hard surfaces.

Frogs’ knees are bent while they are resting, which means that they are under continuous strain. The cartilage helps alleviate the strain on the kneecaps, keeping the knees loose for when the frog needs to jump. The cartilage in a frog’s knees is similar to a patella in a human’s knees (CTNF).

Frogs Have Backbones

Frogs have a backbone which is a series of bones called vertebrae. The purpose of the backbone is to give the frog’s body structure, support its weight, and allow the frog to perform and survive. A frog’s backbone runs down the length of the body, from its head to its tailbone. 

Do Frogs Have Bones-min

The other important role the backbone plays is to protect the spinal cord. This is a series of nerves that run from the brain, through the backbone and connect to all the parts of the body. The spinal cord controls the movements vertebrates make and connects the body to the brain. If the spinal cord is injured, it can result in paralysis.

Vertebrae Make Up a Frog’s Backbone

Frogs have 10 vertebrae. The 1st vertebra is called the atlas and it is the bone that connects to the base of the frog’s skull, allowing it to move its head. The next seven vertebrae are abdominal vertebrae as they are in the abdomen of the frog. Then are the sacrum, ileum, and urostyle.

Most vertebrates have tailbones that connect to the spinal column, but, unlike other amphibians, frogs and toads do not have tails. They are called Anurans, or tailless amphibians. Amphibians with tails include salamanders, newts, and caecilians. 

Learn more about a frog’s backbone in this guide on our blog

Do Tadpoles Have a Backbone?

When frogs reproduce, they lay eggs. These eggs hatch into larvae called tadpoles, which need a water source to grow and develop into adult frogs. Tadpoles resemble fish as they swim around. Frogs can remain in the tadpole stage for days, weeks, or even years, depending on the species of frog and the climate of their environment.

Frogs tadpoles do not have bones or backbones because their bodies are supported by cartilage. As the tadpoles develop into adult frogs, their skeletal system grows. This allows them to swim and eat the food they need to develop and transform. Eventually, the tadpole develops legs and lungs. 

Once they reach the froglet stage, frog tadpoles are vertebrates with a full skeleton. By that time, their gills have also disappeared and they have lungs that allow them to breathe on land. They can also breathe in water through their skin thanks to osmosis.

Do Frogs Have Cervical Vertebrae?

Cervical vertebrae are the vertebrae that make up the neck. They are extremely strong and flexible and allow vertebrates to move their heads in different directions.

Frogs only have 1 cervical vertebra, the atlas, connected to the base of the skull to support their head, allowing it to move up and down. The length of motion of a frog’s head is much more limited than that of humans. Because of this, it is generally considered that frogs do not have a neck.

Since frogs only have one cervical vertebrae (the atlas), they can only move their head up, down, forward, or back. They cannot turn their head to the left or to the right. This is why you generally see frogs turning their entire bodies to fully observe something next to them. Luckily, frogs have excellent 360° vision, reducing the need for them to turn their head in the first place.

Does a Frog Have More Bones Than a Human Does?

Humans and frogs are both vertebrates and both have bones, but there are major differences between the two species. A grown human has 206 bones yet a frog only has about 50 bones. That is a big difference. 

Here are a few other similarities and differences between a frog skeleton and a human skeleton:

Skeletal StructureFrogsHumans
VertebrateYesYes
BackboneYesYes
CartilageYesYes
Knee CartilageYesNo
Fused VertebraeYesNo
NeckNoYes
Fixed PelvisNoYes
Vertebrae1024
Number of Bones~50206
Ribs012

Here are a few differences between a frog skeleton and a human skeleton:

  • Since a frog only has one cervical vertebra, it has no neck and limited movement of the head. Humans have seven cervical vertebrae, giving us necks and a wide range of motion.
  • Frogs do not have ribs. Instead, they have rib-like structures that are part of the spine. Humans have 12 pairs of ribs that are separate bones from the spine.
  • To assist with jumping, a frog’s pelvis can slide up and down its spine. Human pelvises are fixed in place.
  • Frogs have 24 main bone structures with about 50 bones in total including the distal radioulna, carpals, metacarpals, phalanges, scapulas, coracoids, sternum, adioulna, tibiofibula, suprascapula, humerus, sacrum, ilium, ischium, femur, tarsals, astragalus, calcaneus, metatarsals, atlas, sacral vertebra, urostyle, tarsal bones, and astragalus.

While frogs have many unique skeletal characteristics, there is a surprising number of similarities between frogs and humans or larger mammals. Although frogs appear to be smooth and completely flexible in appearance, most of their gravity and physics-defying traits are supported by their bones. 

More About Frog Anatomy

Despite the fact that frogs don’t have many bones, their skeletons have evolved over time to perfectly suit their needs depending on the species and how they move.

Learn more about frog anatomy on our blog:

Common Questions About Frog Bones

How many bones do frogs have? Frogs have 24 main bone structures with about 50 bones in total including the carpals, metacarpals, phalanges, scapulas, coracoids, sternum, adioulna, tibiofibula, suprascapula, humerus, sacrum, ilium, ischium, metatarsals, atlas, sacral vertebra, urostyle, tarsal bones, and astragalus.

What are frog bones? Frogs bones include the distal radioulna, carpals, metacarpals, phalanges, scapulas, coracoids, sternum, adioulna, tibiofibula, suprascapula, humerus, sacrum, ilium, ischium, femur, tarsals, astragalus, calcaneus, metatarsals, atlas, sacral vertebra, urostyle, tarsal bones, and astragalus.

What are frog bones made of? A frog’s bones are made up of calcium carbonate and calcium phosphate. 

Why frogs cannot turn their head? Frogs cannot turn their head because they only have 1 cervical vertebra (the atlas) connected to the base of their skull, so it is generally considered that frogs do not have a neck. However, they have excellent 360° vision, reducing the need for them to turn their head in the first place.

Do frogs have bones? Frogs have bones and a backbone made that is lightweight to give their bodies a structure while also allowing them flexibility for hopping, jumping, swimming, digging, crawling, or climbing depending on the species.

Sources

Abdala, V., Vera, M.C. and Ponssa, M.L. (2017), On the Presence of the Patella in Frogs. Anat. Rec., 300: 1747-1755. https://doi.org/10.1002/ar.23629

Pilkington, J. B., and Simkiss, K. (1966). The mobilization of the calcium carbonate deposits in the endolymphatic sacs of metamorphosing frogs. J. Exp. Biol. 45:329

University of Wisconsin, Lab 10: Tetrapod Vertebrates