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 were rebuilt for fast, three-dimensional movement before there was a wing to use them on. The equipment for flight came first, and the flight came after.

Dating & uncertainty

The oldest unambiguous pterosaurs are already fully flying animals, which leaves the transition unrecorded. Their closest known relatives, small running reptiles called lagerpetids, were identified only 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