article: Ichthyostega
links: Morphology (biology) Paraphyly Crown group Stegocephali Panderichthys Acanthostega Greenland Animal Chordate Tiktaalik Lissamphibia Elpistostegalia Pelagic zone Pinniped Devonian Eusthenopteron Sarcopterygii Osteichthyes Tetrapoda Vertebrate Triassic