LIFE × EVOLUTION

A Hot Spring That Petrified a Swamp

~407 million years ago

Phanerozoic · Paleozoic · Devonian

Silica-rich water from a hot spring in what is now Aberdeenshire flooded a wetland and turned it to stone, cell by cell. Here and there the rock holds plants still standing where they grew, and with them the oldest known nematode worm, the oldest mites and springtails, a centipede, the earliest harvestman with its breathing tubes and its genitals intact, and the chewing mouthparts of the first true insect. It even holds their droppings.

Why it matters

Nowhere else does an early land ecosystem reach us largely intact: who ate whom, who lived on whom, which partnerships were already running. The droppings alone are enough to challenge the old assumption that several of these animals fed on spores. Everything else of that age is fragments.

Dating & uncertainty

Dated to the Early Devonian at about 407 Ma. The deposit is a snapshot of a hot spring, not of the Devonian world: its flora is low in diversity and tolerant of hot, alkaline, brackish water, so what it preserves may be an unusual community rather than a typical one.

Sources

1. Dunlop et al. (2018), Philosophical Transactions of the Royal Society B · Terrestrial invertebrates in the Rhynie chert ecosystem
2. Channing (2018), Philosophical Transactions of the Royal Society B · A review of active hot-spring analogues of Rhynie: environments, habitats and ecosystems
3. Trewin (2007), Novartis Foundation Symposium · The Rhynie cherts: an early Devonian ecosystem preserved by hydrothermal activity

Earth history as one day

21:50:542 h 9 min before midnight

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