LIFE × EVOLUTION

The First Flying Vertebrates

~220 million years ago

Phanerozoic · Mesozoic · Triassic

A membrane stretched from a hugely elongated fourth finger back to the ankle, and a reptile flew under its own power. Insects had been doing it for a hundred million years; nothing with a backbone had. The oldest pterosaurs are already complete fliers, so the transition itself is missing, but their nearest known relatives have been found: small running reptiles that never flew, and that already carried the enlarged balance organs a flier needs.

Why it matters

Powered flight has appeared four times in animals, and this was the second. What the running relatives show is the order of assembly: the brain and the inner ear had already taken their pterosaur form in animals that never left the ground. The equipment came first, and flight came after.

Dating & uncertainty

The figure shown here rounds the age of the oldest unambiguous pterosaurs, which come from the Upper Triassic and are already fully flying animals. Because the transition that produced them is unrecorded, the origin of the group is older than that date by an amount the fossils do not give. Their closest known relatives, small running reptiles called lagerpetids, were only recognised as such in 2020, and they shortened the gap without closing it.

Sources

1. Ezcurra et al. (2020), Nature · Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria
2. Foffa et al. (2025), Nature Ecology and Evolution · Climate drivers and palaeobiogeography of lagerpetids and early pterosaurs
3. Benton (2021), Gondwana Research · The origin of endothermy in synapsids and archosaurs and arms races in the Triassic

Earth history as one day

22:50:131 h 10 min before midnight

if Earth’s 4.54 billion years were compressed into a single day