Class (Classes)

Animal Taxonomy Pyramid Diagram

Biology definition: Class is a taxonomic rank (a taxon) consisting of organisms that share a common attribute; it is further divided into one or more orders. In the biological classification of organisms, a class is a major taxonomic rank below the phylum (or division) and above the order. For example, class Mammalia belongs to the phylum Chordata. Class Mammalia consists of various orders, such as Chiroptera (bats), Primates (apes), Carnivora (dogs, cats, jaguar, bears, etc.), Cetacea (whales), Proboscidea (elephants), and many others.

The phylum group is then divided into even smaller groups, known as animal classes. The Chordata phylum splits into these seven animal classes:

  1. Agnatha (jaw-less fish) – Primitive jawless fish including lampreys, hagfishes, and extinct groups.
  2. Chrondrichtyes (cartilaginous fish) – Composed of fish with skeletons composed of cartilage. Includes two subclasses: Elasmobranchii (rays, skates, sawfish, and sharks); Holocephali (chimaeras–ghost sharks).
  3. Osteichthyes (bony fish) – Includes saltwater and freshwater fish with bony skeletons like eels, anglerfish, clown fish, swordfish, and catfish, carp, trout, and salmonids.
  4. Amphibia (amphibians) – Four-limbed, ectothermic vertebrates, including frogs, toads, salamanders, and newts.
  5. Reptilia (reptiles) – Vertebrates with dry skin and scales such as snakes, turtles, lizards, and crocodilians.
  6. Aves (birds) – Warm-blooded, egg-laying animals characterized by two wings, two legs, and feathers.
  7. Mammalia (mammals) – Warm-blooded four-legged (or two-armed, two-legged) animals that breathe with lungs and birth live young.


  • Austin, S. (2023, January 30). Classification of Animals: The Complete Guide. A-Z-Animals. Retrieved September 25, 2023, from Link
  • Class. (2023). In BiologyOnline. Link
  • Encyclopædia Britannica, Inc. (2023). Animal Taxonomy [Photograph]. Britannica. Link

Additional Sources of Information

  • NatureFiji-MareqetiViti is Fiji’s only domestic NGO working solely for the conservation and sustainable management of Fiji’s unique natural heritage – Link