New fossil findings reopen debate on vertebrate land transition

Paleontologists have long held that the first vertebrates to move from water to land passed through an amphibious, tadpole-like body form in a process of metamorphosis. New fossil evidence is challenging that established view, researchers reported. Data on the morphology of early tetrapods suggest the adaptation to land may have proceeded differently than previously assumed. The findings indicate that the transition needs to be reassessed, whether as a gradual shift or a more complex evolutionary process, according to the team. The study raises new questions about how the animals developed the capacity for movement and respiration on land, the researchers said. They added that further work on additional specimens would be needed to clarify the sequence of events.