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The Difference Between a Shark and a Dolphin Skeleton – Explained

The Difference Between a Shark and a Dolphin Skeleton – Explained

Sharks and dolphins are both sleek predators that live in the ocean. Depending on the species, sharks and dolphins are roughly the same size and weight.

However, there are major differences in their skeletons. Shark skeletons are not made of bone.

The shapes of the skull, teeth, and spines differ between sharks and dolphins.


How Can You Tell the Difference Between a Shark and Dolphin Skeleton?

Shark skeletons are made from cartilage. Dolphin skeletons are made from bones. Shark skulls are longer and symmetrical, while dolphins have asymmetrical skulls with a prominent bulging forehead. Most sharks have rows of differently-shaped teeth, while dolphins only have 1 row of teeth that are mostly the same shape.


Cartilage Vs. Bone

Shark skeletons aren’t made of bone but of calcified cartilage. Our ears and nose tips are made of cartilage.

Cartilage is a sturdy but flexible tissue that, for animals like people and dolphins, forms the core for bones to harden around.

Since cartilage does not preserve well over time, most of what we know about ancient sharks is from their teeth, scales, and shark bite injuries in the bones of other animals.

Shark teeth are made up of dentin, which decays very slowly.

One partial fossil that did have cartilage remaining was that of a long-extinct Gogo shark found in 2005. The fossil was 880 million years old.

The cartilage was the same in design as the cartilage of modern sharks. Scans of it showed that the cartilage contained remnants of bone cells.

This means that sharks most likely had ancestors with conventional bone skeletons. Sharks evolved skeletons of cartilage and not bone because the lightweight cartilage made them faster and more agile swimmers.

Sharks are not the only creatures that have cartilage for bones. Closely related are rays and skates. All live in the sea.

Sharks, rays, and skates are some of the most complex animals without a bone skeleton known.

This does not mean they are more primitive or less evolved than dolphins or creatures with bone skeletons. They are just different.

So, if you’re wondering about how many bones sharks have, you already know. If not, then read the article about it on this website.


Skull Differences

Shark skulls vary in shape depending on the species, but on the whole, they are sleek. Some have bizarre shapes, such as the distinct sledgehammer-like skull of the hammerhead shark, or the elongated skull of the saw shark.

Shark skulls are also symmetrical, meaning they have the same shape on both sides.

Dolphin skulls are asymmetrical, meaning they are shaped differently on either side. They also have a large bulbous forehead.

The weird shape and the domed top help the dolphin with echolocation. Organs and soft tissues in their heads produce clicks that send soundwaves to bounce off of objects and back to the dolphin.

This helps dolphins navigate and hunt when in murky or dark water.

Dolphin skulls also have a huge nostril at the top, called a blowhole. As dolphins are mammals, there is a need for them to breathe air.

Sharks are fish and breathe in the water with gills. Gills do not have any bones or cartilage in them, and so do not appear in shark skeletons.


Tooth Differences

Shark teeth are made of calcified or hardened dentin. Dentin is the stuff inside the teeth of many mammals, including people.

Dentin is actually harder than bones, which is why they decay so slowly, making them often the only parts left of long-extinct shark species. Sharks constantly grow teeth throughout their lives.

Dolphins, in contrast, have only one set of teeth during their lives. Their teeth are similar to other mammals’ teeth, made up of enamel over dentin.

Dolphin teeth grow like rings on a tree. The teeth also contain any heavy metals or other contaminants found in the fish dolphins eat.

Scientists at Massey University and the Otago University’s Faculty of Dentistry use the teeth of bottlenose dolphins to determine how polluted the oceans were years or even decades ago.

Both shark teeth and dolphin teeth are, for the most part, triangular, although dolphin teeth are more cone-like than shark teeth. Shark teeth tend to have serrated edges, while dolphin teeth tend to have smoother edges.

Dolphins have teeth of equal size while shark teeth differ in size, depending on where they are in the mouth. Porpoises, a kind of dolphin, have teeth shaped like spades.

There are far more shark species than dolphin species, so some shark teeth are bizarre. The frilled shark has teeth that point back towards the shark’s throat.

Frilled shark teeth are 25 rows of long pronged needles rather than triangles. Most shark species have rows of teeth. Dolphins, like people, only have one row of teeth.


Spinal Differences

Sharks have differently shaped spines than do dolphins. They tend to be straighter.

Their vertebrae are also different. They are small and lack any kind of ridges.

Like most mammals, dolphins have ridges on their vertebrae. The topline of a shark’s spine is mostly smooth with a dorsal fin, while the topline of a dolphin’s spine looks like a series of spikes.

Both living sharks and dolphins sport dorsal fins or fins that point up from the backbone. You can mostly see them poking out through the water.

Sometimes, the dorsal fin is all a swimmer or boater can see of an animal. In skeletons, dolphins lack any dorsal fins because these fins do not have bones.

Shark skeletons will have dorsal fins.


Frequently Asked Questions About Telling the Difference Between a Shark and Dolphin Skeleton


How Do You Know If It’s a Dolphin or a Shark?

Often, people only see a dorsal fin sticking out of the water. Sharks can have more than one dorsal fin. Their fins are more triangular in shape. Dolphin dorsal fins tend to curve.


Do Sharks Have More Teeth than Dolphins?

Sharks generally have more teeth than dolphins, and have multiple rows of teeth, while dolphins only have one row. Dolphins, depending on the species, have anywhere from 80 to 240 teeth. The whale shark has 3,000 very small teeth. Fortunately, those teeth are only about six millimeters long.


The Least You Need to Know

There are various differences between the skeletons of dolphins and sharks. Dolphin skeletons are made of bone, while shark’s skeletons are made of cartilage.

Dolphin skeletons lack dorsal fins. The vertebrae have spines, while shark skeletons do not.

Dolphin skulls have blowholes and have a large, bulbous forehead. Shark skulls vary wildly according to species but tend to be sleeker than dolphin skulls and lack a round forehead.