Evrim Yazgin
Cosmos science journalist
Fossilised trees found in southwest England form the earliest known forest on Earth.
The find highlights changes in these ancient forests which went from being relatively primitive to becoming well established over just a few million years. It is described in a paper published in the Journal of the Geological Society.
Previously, the oldest fossil forest in the world could be found in New York state in the US. Called the Gilboa fossil forest it is 386 million years old.
At 390 million years, the newly discovered fossil forest just edges Gilboa out for age.
It was found at the Hangman Sandstone Formation. The geological site is on the coast in Devon near the Hangman cliffs which reach up to 318 metres, England’s highest sea cliff.
Appropriately, the fossil forest is from the middle of the Devonian period (419–359 million years ago) which was named in the 1830s after fossils discovered in the same region of England’s southwest. During this time, the UK was part of an ancient continent called Laurentia which sat just south of the equator. The climate was warm and dry.
The Devonian is commonly referred to as the “Age of Fishes” because of its diverse and abundant marine life. But it’s also the period which, toward its end, saw the evolution of some of these fishes to breathe air and walk on land.
It’s also in the Devonian when the first vascular plants evolved.
But the forests fossilised in Devon and New York were not at all like the treed forests we know today.
Unlike Gilboa, which has a complex array of ancient plants, the newly discovered forest hosts one type of plant called cladoxylopsids. They disappear from the fossil record about 320 million years ago.
Cladoxylopsids are thought to be closely related to ferns and horsetails. While they looked like palms, palm trees weren’t to evolve for another 300 million years.
Older trees have been found around the world. It’s believed that plants began to colonise land about 500 million years ago. But the Devon fossilised forest is the oldest example of plants growing close together in large numbers.
Between the plant fossils, the researchers also found tracks of the critters that populated the ancient forest floor. These animals would have been no larger than small arthropod relatives of today’s insects, crabs and spiders.
