Cooksonia

One of the first plants with pipes for water.

Our sources give no reliable size for Cooksonia, so this outline of its body shape is not drawn to scale.

When: The oldest fossils are from about 427 to 423 million years ago, in the Silurian
Where: Wales, Ireland and elsewhere

A dark Y-shaped fossil stem, forking in two, on grey rock. — Cooksonia pertoni from Wales, in the collections of Amgueddfa Cymru, the National Museum Wales.Amgueddfa Cymru - Cooksonia pertoni - 211800 by Amgueddfa Cymru – Museum Wales, CC BY-SA 4.0, via Wikimedia Commons. Resized. This version is shared under CC BY-SA 4.0 too.

Cooksonia was a small, simple plant: thin stems that fork in two, as you can see in the fossil below. It is the earliest well-preserved vascular plant, a plant with tubes inside it to carry water, as nearly every plant you see today has.

The three oldest places in the world where Cooksonia fossils are found are in Wales and Ireland. In 2024, tiny crystals of zircon in the rock were dated: the rocks at Capel Horeb in Wales can be no older than about 427 million years, and those at Cwm Graig Ddu about 423 million.

Plants like it may have changed the planet. As they spread, they had a deep effect on how oxygen, carbon dioxide and nitrogen moved between rock, sea and air.

Cooksonia: 427 to 419 million years ago. That is 9% of the way back to the Earth’s birth.Periods from the ICS chart

Found in Britain. See where Britain was at the time in Britain’s journey.

Also in onto the land

Tiktaalik roseae A fish on the way to becoming a four-legged animal
Arthropleura A giant millipede, the largest arthropod known

Sources

H. K. Garza and others, Geological Magazine, Detrital U-Pb ages for the first well-preserved vascular plant Cooksonia from the UK and Irish macrofossil record (2024)