Around 355 million years ago, perhaps earlier
Life away from water
Amniotes, the group that includes reptiles, birds and mammals, could live and breed away from water. Their origin may be much older than once thought.
Deep history See it on the atlas
Why it matters
Amniotes are named for the membranes that protect their embryos, which freed them from having to return to water to breed. Mammals, including us, belong to one great branch of amniotes; reptiles and birds belong to the other.
What the evidence shows
- A 2025 study described clawed footprints from early Carboniferous rocks in Victoria, Australia, and interpreted them as made by an amniote.
- If that interpretation holds, amniotes arose some 35 to 40 million years earlier than the oldest known amniote body fossils suggest, and the first four-limbed animals must have appeared deep in the Devonian.
What is uncertain
- Footprints rarely identify their maker with certainty. The precise origin date of amniotes remains open.
Sources
What it supports: Clawed footprints from early Carboniferous rocks in Victoria, Australia, interpreted as made by an amniote. If correct, amniotes arose much earlier than their oldest body fossils suggest.
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