Animal Classes is a subcategory which illustrates a taxonomic sub-grouping of animals. On the order of biological ranks, Animal Classes is between Phylum and Order, and is the fourth of eight biological taxonomic ranks. Animal Classes are generally subjective and can vary depending on the animal or taxonomist who is specifying the animal. Popularly, there are five major animal classes which include mammals, birds, fish, reptiles, and amphibians. The following collections have been organized to better understand and browse the collections of animals by their specific classes.