Division II : Gnathostomata
Classification of Animal Chordates of Class 11
Jawed vertebrates having true jaws and paired limbs. All the fish and fish-like aquatic gnathostomes are placed in the superclass Pisces, whereas all the four footed terrestrial gnathostomes are placed in the superclass Tetrapoda.
Differences between Pisces and Tetrapoda
| Pisces | Tetrapoda |
| Exclusively aquatic. | Aquatic or terrestrial. Some arboreal and aerial. |
| Paired limbs, if present, as fins. | Paired pentadactyl limbs present. |
| Median fins present. | Median fins absent. |
| Skin usually moist and scaly. | Skin usually dry and cornified. |
| Respiration aquatic, by gills. | Respiration aerial, by lungs. |
| Sense organs functional in water. | Sense organs functional in air. |
