Tiktaalik-375 MYA- Paleozoic- Devonian
The Tiktaalik had a very special role in the history of Earth as they were the first species of fish to travel out of the water into the land which in turn was very pivotal as this served as the start of animal life on land which eventually brought us around so had they not done that, we would most likely still be in water.
The Tiktaalik needed to have some type of way to walk, so they got leg looking things. They developed bones which helped create the body parts. This organism is important enough because it was one of the first creatures to walk on land which essentially would serve as a start for animal life on land which eventually brought humans.