<P> Ediacara biota appear during the Ediacaran period , while vertebrates , along with most other modern phyla originated about 525 Ma during the Cambrian explosion . During the Permian period , synapsids , including the ancestors of mammals , dominated the land , but most of this group became extinct in the Permian -- Triassic extinction event 252 Ma . During the recovery from this catastrophe , archosaurs became the most abundant land vertebrates ; one archosaur group , the dinosaurs , dominated the Jurassic and Cretaceous periods . After the Cretaceous -- Paleogene extinction event 66 Ma killed off the non-avian dinosaurs , mammals increased rapidly in size and diversity . Such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify . </P>
<P> Ediacara biota appear during the Ediacaran period , while vertebrates , along with most other modern phyla originated about 525 Ma during the Cambrian explosion . During the Permian period , synapsids , including the ancestors of mammals , dominated the land , but most of this group became extinct in the Permian -- Triassic extinction event 252 Ma . During the recovery from this catastrophe , archosaurs became the most abundant land vertebrates ; one archosaur group , the dinosaurs , dominated the Jurassic and Cretaceous periods . After the Cretaceous -- Paleogene extinction event 66 Ma killed off the non-avian dinosaurs , mammals increased rapidly in size and diversity . Such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify . </P>
the first group of animals to live on land was the
the first group of animals to live on land was the
synapsids
synapsids