The 390-million-year-old forest landscape, archived within the Eifelian Hangman Sandstone Formation of Somerset and Devon in England, is roughly 4 million years older than the previous record holder, which was found in New York State, the United States.

Fossilized ripple marks on the floor of the Calamophyton forest. Image credit: Neil Davies.

The Devonian period (419-359 million years ago) was arguably the most crucial chapter in the evolution of Earth’s land biosphere.

Non-marine environments at the end of the preceding Silurian period accommodated nascent invertebrate communities in near-water settings, witnessed frequent invasions of freshwater bodies by jawless fish, and hosted scattered stands of small, simple plants in coastal regions, but their equivalents 60 million years later were unrecognizable.

By the end of the Devonian period, the range of permanent invertebrate habitats had expanded to even the driest non-marine settings jawless and jawed fish had become enduringly resident in lakes and rivers, evolutionary developments amongst vertebrates meant that tetrapods traversed river margins and floodplains, and there had been an explosion in disparity amongst plants that saw vast inland forests of multi-meter tall trees in addition to a huge diversity of other plant groups, including woody shrubs.

This fundamental transformation not only triggered novel interactions between different organisms, such as the rise of herbivory and detritivory, but also saw many new organism-environment interactions take shape.

“The Devonian period fundamentally changed life on Earth,” said Professor Neil Davies, a paleontologist at the University of Cambridge.

“It also changed how water and land interacted with each other, since trees and other plants helped stabilize sediment through their root systems, but little is known about the very earliest forests.”

A reconstruction of the Calamophyton forest. Image credit: Peter Giesen / Chris Berry.

A reconstruction of the Calamophyton forest. Image credit: Peter Giesen / Chris Berry.

The fossils discovered by Professor Davies and colleagues are the oldest fossilized trees ever found in Britain, and the oldest known fossil forest on Earth.

The fossilized trees, known as Calamophyton, were found near Minehead on the south bank of the Bristol Channel, England.

They at first glance resemble palm trees, but they were a ‘prototype’ of the kinds of trees we are familiar with today. Rather than solid wood, their trunks were thin and hollow in the center.

They also lacked leaves, and their branches were covered in hundreds of twig-like structures.

These trees were also much shorter than their descendants: the largest were between 2 and 4 m tall.

As the trees grew, they shed their branches, dropping lots of vegetation litter, which supported invertebrates on the forest floor.

“This was a pretty weird forest — not like any forest you would see today,” Professor Davies said.

“There wasn’t any undergrowth to speak of and grass hadn’t yet appeared, but there were lots of twigs dropped by these densely-packed trees, which had a big effect on the landscape.”

“This period marked the first time that tightly-packed plants were able to grow on land, and the sheer abundance of debris shed by the Calamophyton trees built up within layers of sediment.”

“The sediment affected the way that the rivers flowed across the landscape, the first time that the course of rivers could be affected in this way.”

“The evidence contained in these fossils preserves a key stage in Earth’s development, when rivers started to operate in a fundamentally different way than they had before, becoming the great erosive force they are today.”

“People sometimes think that British rocks have been looked at enough, but this shows that revisiting them can yield important new discoveries.”

The discovery is reported in a paper in the Journal of the Geological Society.


Neil S. Davies et al. Earth’s earliest forest: fossilized trees and vegetation-induced sedimentary structures from the Middle Devonian (Eifelian) Hangman Sandstone Formation, Somerset and Devon, SW England. Journal of the Geological Society, published online February 23, 2024; doi: 10.1144/jgs2023-204

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