Biology

Is Shark A Mammal Fish Or Amphibian?

There is no way to describe sharks with a single feature; there are hundreds of shark species on the planet, all with different characteristics. Some of these characteristics are relatable to fishes; some link them with mammals and amphibians, so there is always a misperception when it comes to the taxonomic classification of sharks. What do you think, which class do they belong to? Confused?? Don’t be! Let’s find out to clear your thoughts and surprise you.

Are sharks a mammal, fish or amphibian?

Well, the answer to this mythological question is that “sharks are fish”. Wait! Let me explain! So, sharks are categorised as fishes, as they belong to class Chondrichthyes, and secondly the most important feature which distinguishes them from mammals and amphibians is that the skeleton of sharks is made up of cartilage instead of bones. Although many physical characteristics of sharks do resemble mammals and amphibians, they are characterised into Elasmobranch, including all sharks.

Sharks are fish, is it really true?

Yes, sharks are fish but not all fishes are sharks, sharks are known to be cartilaginous fishes because none of their internal features resembles mammals or amphibians. The gills are located on the sides of their head which extracts oxygen from surrounding water which is used by sharks to respire underwater. The anatomy of sharks shows that they are cold blooded fishes without bones and have fins. These characters closely resemble the fishes. 

Why are sharks not categorised as mammals?

All mammals belong to class Mammalia and have unique body features:

  • The presence of mammary glands
  • All mammals are warm blooded
  • Their body is covered with hairs.
  • Their skeleton is made up of bones impregnated with calcium.
  • All mammals have a well developed brain and respire through lungs

Not any of the features shows resemblance with sharks because sharks lack mammary glands and are cold blooded, their skin lacks hair, have cartilaginous skeleton and they do need oxygen for their existence but do not respire the atmospheric oxygen instead they absorb oxygen from water with the help of gills.

Sharks are not grouped along with amphibians, why?

Likewise mammals, amphibians belong to class Amphibia with the following distinctive features:

  • They have the ability to live both in water and on land.
  • They are ectothermic animals
  • Their skin is without scales
  • They do not possess gills and fins
  • They respire through the skin.

This depicts that sharks are not related to amphibians in any of the characters, as sharks live in water, this skin contains scales and respire through gills. Hereafter, it is truly deceitful to consider sharks as amphibians.

What makes sharks different from other fishes?

Another question which makes people curious is concerning the type of fish a shark is?  Let’s go with the flow to clear this inquisitive question out. Almost 95% of all the fishes alive today are bony fishes which means their skeleton is made up of bone but when we discuss sharks, they belong to a very special type of fish – cartilaginous fish.

Usually all other fishes have a single pair of gills while sharks possess 5 pairs of gills which helps them in breathing deep in the ocean. Sharks have the ability to contract and dilate their pupils while all other fishes lack this characteristic. Although both bony fishes and sharks have the ability to lay eggs, the young pups of fishes hardly developed whereas the young ones of sharks complete the cycle of development.

Sharks are carnivores and devious feeders that can eat small fishes or anything they can kill though other fishes feed on a variety of things like plants. Another distinctive feature is that bony fishes are capable of moving their pectoral fins in various directions, which makes them move in backward direction whereas the pectoral fins of sharks do not move thus they lack the ability to swim in backward direction.

What does it conclude?

Sharks belong to the cartilaginous group of fishes, however, they are neither amphibians or mammals but some physical features are related to them, entirely their characteristics correlates with fishes as they have the ability to filter oxygen from the water to respire and use fins for locomotion like all other fishes does. From the details given in this article we have concluded that sharks are fishes!

About the author

Ameer Hamza