1. Subphylum Vertebrata is divided into two divisions, Agnatha and Gnathostomata. Agnatha
Agnatha includes jawless fish-like aquatic.
Vertebrates without paired appendages.
Notochord persists in the adult.
Agnatha includes class-Cyclostomata.
Gnathostomata
It includes jawed vertebrates with paired appendages.
Notochord is replaced partly or wholly by the vertebral column.
It includes jawed fishes (Pisces) and Tetrapoda (amphibia, reptilia, aves and mammals).
Pisces includes all fishes which are essentially aquatic forms with paired fins for swimming and gills for respiration.
Pisces includes cartilaginous fishes (Chondrichthyes) and bony fishes (Osteicthyes).
