EARLIEST TETRAPOD RECORD
- The Ichthyostega still holds some fish-like characteristics.
- Tetrapods are commonly accepted as being monophyletic - that is, a group that contains the latest common ancestor plus all and only all its descendants ie. Osteichthyes
- Osteichthyes is a type of bony fish that tetrapods are thought to have derived from.
- Jarvik in 1980 proposed a diphyletic origin from two separate groups of fossil osteichthyan:
- Living salamanders from porolepiforms
- all other tetrapods (amphibian and amniote) from osteolepiforms
* it has not received support outside Swedish schools.