How Animal Classification Works

In the 1700s, Carl Linnaeus developed an extensive system for classifying animals. Before this system, the animal kingdom was in disarray. People were discovering new animals but had no idea how to organize them. There was no clear link between animals.

After Linnaeus finished his work, researchers could group animals based on a complex system of names. Known as the Linnaeus method, this animal classification system has been around through the centuries. 

The Basics of Animal Classification

Every species of animal has a two-word scientific, Latin name. As a general rule, the scientific name is a combination of the genus and the species. You may even know of a few scientific names, like Ursus maritimus (polar bears). When you write out the name, you should capitalize the genus but not the species. 

Most people refer to animals by their common name rather than their scientific name. But the common name doesn’t tell you much information about the animal itself. When you know the scientific name, you can have a clear understanding of how an animal relates to others. 

With that said, there’s more to animal classification than a scientific name. There are nine categories of animal classifications. The pyramid below indicates all the classifications:

At the top of the system, you find the domains. The domains are Archaea, Bacteria, and Eukarya. Animals fall under the Eukarya category, along with Plantae, Protozoa, Chromista, and Fungi.

The Animal Kingdom and Common Phyla (7)

As mentioned, animals fall under the Eukarya domain. All animals are part of the animal kingdom, and the majority of animals fall under one of seven common phyla. Here’s a breakdown of each phylum and the types of animals you can find in the category.

1. Porifera

This phylum refers to sponges, marine animals that live in the ocean. Every animal in this phylum has no organs and is capable of regeneration. 

2. Cnidaria

Like Porifera, Cnidaria includes marine animals. Jellyfish, coral, and anemones all are part of this phylum. In this phylum, the animals all have tentacles with stinging nematocytes and have a nerve net instead of a central nervous system. 

3. Platyhelminthes

These are parasitic flatworms that have no respiratory or circulatory system. To get oxygen, Platyhelminthes receive oxygen through their bodies. Tapeworms and flukes fall under this category. 

4. Annelida

Slightly more complex than platyhelminthes, this phylum includes segmented and symmetrical worms. They all have a nervous system, sense organs, and respiratory system. In this phylum, you can find earthworms and leeches.

5. Mollusca

This category covers about one-quarter of all marine life. It includes invertebrates with soft, unsegmented bodies. Oftentimes, Mollusca has shells like mussels, clams, and snails. 

6. Arthropoda

Also including invertebrates, Arthropoda animals have exoskeletons and segmented bodies. Scorpions, shrimp, and insects are under Arthropoda.

7. Chordata

In this phylum, you can find animals that have vertebrates. Over time, animals in Chordata grow a cartilaginous skeletal rod that might become a spine. Dogs, humans, and horses are in the Chordata phylum. 

Classes of Animals Example: Chordata (7)

You can break down each one of the phylum groups into an animal class. Although you can also break down all the other phylum into classes, it would take days to read about all the possible categories. Generally, the things people refer to as animals are under the Chordata phylum.

There are seven classes in Chordata. Here’s a closer look at all of the chordates:

1. Agnatha

This category houses primitive jawless fish, like lampreys and hagfish. In addition to having no jaws, most animals in this class have a cartilaginous skeleton.

2. Chrondrichtyes 

More complex than agnatha, this class has fish that have skeletons made from cartilage. Rays, skates, and ghost sharks are examples of Chrondrichtyes. 

3. Osteichthyes 

Any saltwater or freshwater fish that has a bony skeleton is in this class. For instance, carp, salmon, and eels are osteichthyes. 

4. Amphibia

At this point, you might be recognizing some of the classes. Amphibia is the class in which you can find all amphibians, like toads, salamanders, and frogs. 

5. Reptilia 

Reptilia, or reptiles, have scales and dry skin. They also fertilize eggs internally and are cold-blooded.

6. Aves

Another word for the Aves class is birds. As you might expect, this class includes all warm-blooded animals that have wings and feathers. They also all lay eggs.

7. Mammalia

Mammals, or mammalia, are warm-blooded animals with four legs or two arms and two legs. Equipped with lungs, mammals use their lungs to supply oxygen and give birth to live young. 

Animal Orders – Mammalia Examples (5)

You can break classes down even further by looking at the orders. Just as every phylum has a class, every class has an order. However, orders are more varied than the higher levels of organization. What one person considers an order, another may not. Generally, there are around 26 orders of Mammalia.

These are the more common orders of Mammalia:

1. Artiodactyla 

This order contains even-toed hoof animals, like moose and camels.

2. Carnivora

With this order, you can see how confusing classification can be. In addition to including full carnivores, Carnivora also includes some omnivores and herbivores. Most Carnivora have long snouts and nonretractable claws. 

3. Rodentia

Rodentia is a category of gnawing mammals, like beavers and squirrels. Every species in rodentia has no canine teeth and has incisors that continuously grow.

4. Chiroptera

Of all the orders in Mammalia, this one may be the most clear. The order includes flying mammals, which is limited to bats.

5. Primates

This is one order you probably know about because you’re in it. Primates include humans, gorillas, and chimpanzees. Although not all primates have opposable thumbs, many of them do.

Families Example: Carnivora (12)

Even more specific than animal orders are animal families. Once again, you can take an order and split it up into multiple families. All the animals in each family share some very specific characteristics.

Interestingly enough, all of the families are either vertebrates or invertebrates. For a specific example, take a look at the Carnivora order. 

1. Felidae

The domestic housecat is in Felidae, along with all other cats. 

2. Canidae

Dogs, wolves, and coyotes are all in the Canidae family. 

3. Ursidae

In this family, you can find bears. Polar bears, sun bears, and panda bears are examples of Ursidae. However, despite their appearance, koalas are not bears and are not Ursidae.

4. Mustelidae 

Similar in appearance, weasels, badgers, and otters are the family Mustelidae. 

5. Procyonidae 

Raccoons and coatis are the family Procyonidae. Generally, they have slender or stocky bodies and medium or long tails. Their fur is often gray or brown. 

6. Mephitidae 

For examples of Mephitadae, look no further than skunks and stink badgers. As you may know, these animals are regarded for their ability to produce a foul musk when scared or threatened.

7. Herpestidae

In this family, the only animals are the mongoose and the meerkat. 

8. Hyaenidae

This highly specific family only contains the hyena. While there are three hyena species that are scavengers, there is one species that only eats termites. Called the aardwolf, this hyena can eat as many as 300,000 termites in a single night. 

9. Viverridae 

Genets, linsangs, and civets are examples of this family. Usually, animals in this family have erect ears and small heads. 

10. Otariidae 

If you want to know where sea lions and fur seals belong in the classification system, it’s under Carnivora Otariidae.

11. Phocidae 

All true seals fall under the Phocidae family. 

12. Odobenidae

There’s only one species in this family – the walrus, or Odobenus rosmarus. 

Genus Examples: Felidae (4)

Before the final animal classification category, there’s the genus. Every family has one or more genera, and all the animals in a genus are closely related. Here are a few examples of genera under Felidae. Keep in mind that these aren’t all the genera. 

1. Felis

Small cats and domestic cats are in the Felis genus.

2. Panthera

In this genus, there are tigers, lions, and other large carnivore cats. Despite the similarity in names, panthers are not in the Panthera genus. 

3. Pumas

Panthers belong in this genus along with cougars. 

4. Leopardus 

There are nine species in this genus, such as ocelots, kodkods, and margays. It’s known as the spotted cat genus.

Detailed Examples of Animal Classification

If you want to fully understand the classification system, you should look at a real-life example. The red fox is a North American animal. It has the scientific name of Vulpes vulpes.

Based on the scientific name, you can tell that the species name is Vulpes and the genus name is also Vulpes. The family is Canidae, the order is Carnivora, and the class is Mammalia. As you might expect, it’s in the Chordata phylum. 

Broken down, the classification system for a red fox looks like this:

Scientific Name: Vulpes vulpes

• Domain: Eukarya
• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Carnivora
• Family: Canidae
• Genus: Vulpes
• Species: Vulpes

Here’s another example. This time, take a look at the blue whale.

Scientific Name: Balaenoptera musculus

• Domain: Eukarya
• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Cetacea
• Family: Balaenopteridae
• Genus: Balaenoptera
• Species: Balaenoptera musculus

Staying Updated on the Latest in Animal Classification

To this day, animal classification is still changing. Every day, scientists make new discoveries. Using information they learn about animals and evolution, taxonomists are able to fine-tune the classification system.

As long as you can understand the basics of animal classification, you’ll have no trouble understanding whatever changes come up.