A FOSSILISED tree stump dumped on a Poole beach was growing at a time when dinosaurs roamed the earth.

Now a three-ton lump of rock, the fossil dates from 140 million years ago and was transported to Branksome Chine with a consignment of Purbeck stone, destined to become part of one of the Borough of Poole’s new rock groynes.

Workmen spotted the unusual rock, which clearly shows the tree’s grain and put it to one side at the Dean and Dyball compound where the £1.9m coastal defence works project is underway.

Local geologist Jo Thomas, who saw it as she walked along the promenade, said: “There are a few tree stumps around the place but that is a really nice one.”

She said the pine tree, similar to a cypress or juniper, would have been growing on Portland at a time when it was on the edge of a freshwater lagoon that stretched part-way across France.

The continent was much further south than it is now, on a level with Cairo and it would have been much warmer, the earth teeming with dragonflies and beetles we would recognise and dinosaurs we would not.

As the freshwater evaporated, leaving salty water, the fallen tree absorbed silica, enabling it to be preserved, rather than rotting away.

Now 140 years later, this slab of Purbeck stone – three feet tall and measuring four to five feet across – thought to be from the Cretaceous period, is likely to be displayed on the prom.

“If we can encourage everybody to look at the rocks and enjoy them, as well as using them for rock groynes, that would be nice,” said Jo.

A similar fossilised tree stump is displayed at Broadstone Cemetery, on the grave of Alfred Russel Wallace, the man who co-discovered the theory of natural selection along with Charles Darwin.

Borough of Poole ranger Dave Price said: “The geology of the coast is quite interesting and it really would be good if we could make a feature of this fossil.”