Aparición de los primeros Tetrápodos

• Tetrapod trackways from the Middle Devonian period of Poland:
  https://www.youtube.com/watch?time_continue=4&v=YgGwBm4HI8Q
• Evoution has landed:
  http://www.youtube.com/watch?v=B08lugqU3B8
• Tetrapod Evolution:
  https://www.youtube.com/watch?v=3xzMXYdw8HQ
• The Origin of Four-Legged Animals:
  https://www.youtube.com/watch?v=zK8XGEDcTfo
• When Fish First Breathed Air:
  https://www.youtube.com/watch?v=E1h4kgt2520
• Evolutionary Experiments in the Early Tetrapod Form:
  https://www.youtube.com/watch?v=qBVjzWcuQd8
• Caminando con monstruos vida antes de los dinosaurios:
  https://www.youtube.com/watch?v=6V70RXR99Kw