from the world's big
This is the oldest fossil ever found belonging to the line that leads to us.
Phylogeny is the biological development and history of an organism or its class. Paleontologists have been researching the class Mammalia’s phylogeny for some time, particularly its trajectory from tiny rodent-like creatures in the late Triassic 200 million years ago, to modern-day humans. There are currently around 5,000 mammals on the planet, and it's a very diverse group at that.