Phylum

Phylum is the taxonomic category that lies just above class. Several classes that resemble one another in a few basic features are grouped together to form a phylum.

In animals, the classes that include fishes, amphibians, reptiles, birds and mammals are all brought together into a single phylum. They are united by shared features such as the presence of a notochord and a dorsal hollow neural (nerve) system, and on this basis they are placed in the phylum Chordata. …