Arthropods colonise the land
Millipedes and the first arachnids leave the water, breathing air through spiracles.
- When
- Known to
- ± 5 million years
- Era
- Silurian, Paleozoic
Silurian rocks yield the earliest arachnids and myriapods, animals equipped with spiracles and book lungs for breathing air. They fed on the fungal and algal crusts and the decaying remains of early plants. The famous Scottish millipede Pneumodesmus, long cited as the oldest air-breathing animal at 425 million years, was re-dated by zircon in 2017 to about 414 million — Early Devonian — a useful reminder of how much these records depend on the dating of the rock rather than the fossil.