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How to Identify Vertebrates

Vertebrates are animals with a backbone and an internal skeleton. Their skeleton consists of cartilage and bone, a skull with a brain, and limbs. The outer surface of their body is covered by feathers, skin, scales, fur or hair, or some combination of the above [source: Britannica]. There are five classes of vertebrates. The easiest way to determine what class a vertebrate belongs to is by looking at the body covering. Here is a list of the vertebrates' classes and the different body coverings.

  • Fish -- scales
  • Amphibians -- smooth or bumpy skin
  • Reptiles -- scales
  • Birds -- feathers
  • Mammals -- fur and hair [source: New York]

Here are some of the characteristics of each class.


  • Fish are ectothermic or cold-blooded [source: National Aquarium].
  • Fish are often covered with scales.
  • Fish have fins that give them stability.
  • Fish breathe through their gills.
  • Fish have tails that can either be curved, forked or crescent shaped.
  • Fish have eyes on the sides of the head [source: National Aquarium].


  • Amphibians are ectothermic or cold blooded.
  • Amphibians have smooth thin skin, without scales, hair or feathers.
  • Amphibians lay their eggs in water.
  • Amphibian adults breathe with lungs and live outside water.
  • Amphibians have a three-chambered heart.
  • Amphibians have legs and a tail.


  • Reptiles are ectothermic or cold blooded.
  • Reptiles have skin with scales.
  • Reptiles usually have a three-chambered heart, though some have four chambers.
  • Reptiles have legs and a tail.
  • Reptiles lay eggs in a sac [source: Georgia Perimeter College].


  • Birds are endothermic or warm blooded
  • Birds have skin that's covered with feathers.
  • Birds have a four-chambered heart.
  • Birds have wings.
  • Birds lay eggs [source: Britannica].


  • Mammals are endothermic or warm blooded
  • Mammals have hair or fur.
  • Mammals have mammary- or milk-secreting glands and they feed milk to their young.
  • Nearly all mammals give birth to babies and do not lay eggs [source: Buffalo State University].