While it may not look like it, frogs do indeed have bones. They are vertebrates, just like humans, who have an internal skeletal structure. In fact, just like humans, they have many of the same features, like a skull, backbone, hips, limbs, and digits.
However, frogs have adapted to their unique environment and abilities with a skeleton that’s just as unique as their vocalizations.
Frog Bones Are Specialized
It takes a lot of muscle to jump, swim, and climb, but a frog’s skeletal system plays just as important a role to help accomplish these activities. Depending on the species, their bones may be regular in a microscopic aspect, while other frogs have bones that show signs of hyperossification (excessive thickening).
Frogs Have a Lot of Extra Joints
The extra joints in their legs allow them to fold them in as close as possible to their body, making them smaller and less likely to be seen by prey. It also allows them to wrap their legs around objects like rocks and plants or trees. Their legs have thick muscles to support these extra joints. The extra joints in their arms allow them to “hug” objects, and the ones in their feet and hands allow them to grip tightly.
Frogs Have Five Toes
Frogs have four fingers on their front limbs and five toes on their back feet. All of their digits (fingers and toes) have very long bones with a lot of joints, enabling them to swim fast while in the water and giving them the ability to grip surfaces more easily. Bigger feet also enable them to push off from the ground with more force when jumping.
Frogs Have Very Short Backbones
Frogs only have nine vertebrae (though some species have 10). They are arched with no ribs and connect to very wide hip bones. Frogs don’t have “true joints” between the spinal vertebrae. Their embryonic development produces vertebrae that appear to be hollowed out on the front and at the back or on one side only. The entire backbone serves to protect the spinal cord.
Frogs Don’t Have Ribs
Frogs don’t have ribs, so they breathe differently than humans do. In order to draw air into their body, frogs lower the floor of their mouth, which causes the throat to expand. Then the nostrils open, enabling air to enter the enlarged mouth. The nostrils then close, and the air in the mouth is forced into the lungs by contraction of the mouth’s floor. To eliminate the carbon dioxide in the lungs, the floor of the mouth moves down, drawing the air out of the lungs and into the mouth. Finally, the nostrils are opened, and the floor of the mouth moves up, pushing the air out of the nostrils. Frogs also breathe through the skin.
Frogs Have a “Urostyle” Tailbone
At the end of their short backbone, frogs have a urostyle, which is a long, thin bone. It plays a major role in transmitting thrust from the hind limbs to the frog’s back during limb-driven locomotion or jumps.
It is true that frogs have bones. In fact, as amphibians that jump, swim, and climb, their bones are quite unique. They have evolved over many centuries into the frogs we see today, with internal skeletons adapted to their environment.
- See also: What Does Frog Poop Look Like?