The most primitive foot to walk on land has been described by
It belonged to an animal that lived about 345 million years ago
- in what is now Scotland.
The skeletal remains are the oldest in the fossil record to show
bones that had the ability to move on land.
Dr Jenny Clack, who has studied the specimen, says it
illustrates how life on Earth made the transition from a purely
water-borne existence to one where creatures were able to forage on
"This is the first proper, walking foot," she said. "We have
earlier feet, but they were for paddling - for swimming."
The fossil was unearthed in 1971 from limestone deposits north
of Dumbarton. Held at the Hunterian Museum in Glasgow, it was
thought to be a fish.
Only recently was the surrounding rock cleared away sufficiently
to reveal a creature with legs. One hind limb has a near-complete
foot attached with five digits.
It has been classified as Pederpes finneyae. It was a
short-limbed, large-skulled predator. It was about a metre in length
and may have had the look of an ungainly crocodile.
"It was probably quite a sluggish crawler through the swamps
where it lived," Dr Clack says.
The identification helps close a hole in the early fossil record
of a group of creatures called tetrapods - backboned animals with
four legs or limbs.