One of the biggest questions in evolution is when and how major groups of animals first evolved. The rise of tetrapods (all limbed vertebrates) from their fish relatives marks one of the most important evolutionary events in the history of life. This "fish-to-tetrapod" transition took place somewhere between the Middle and Late Devonian (~400-360 million years ago) and represents the onset of a major environmental shift, when vertebrates first walked onto land. Yet, some of the most fundamental questions regarding the dynamics of this transition have remained unresolved for decades.