Five-year-old Emily Baldry unearthed a fossil buried for 162.8 million years – on her first archeological dig.

Emily, of Pew Hill, Chippenham, had barely started wielding a spade more suited to making sand castles when she found the ammonite, called a rieneckia (collotia) odysseus at the Cotswold Water Park.

She was with dad Jon and grandparents Pam and Les Baldry of Malmesbury, when she made the discovery.

Mr Baldry said: “Emily enjoys digging, usually right in the middle of the back garden, but this was the first time we had ever taken her to something like this.

“She is a very inquisitive little girl and got very excited about going on a proper dig. To find something like this was really very special.

“We had only been digging for a few moments when the spades hit something. We tried to dig around it and that was when we realised the size of it. We didn’t know what to make of it until we realised how excited the resident paleontologist was.”

The fossil, which is from the Jurassic period, weighed around 60 kilos, and needed two men to lift it out of the ground and carry it away from the site.

Neville Hollingworth, a paleontologist who volunteers at the water park during organised digs, said: “It is quite spectacular, and all the more special that a little girl discovered it.

“To give you some idea of how rare this is, I have been looking for these for 25 years, and have only ever found three. This is also the biggest of its type that I have ever seen. They are incredibly rare. It was very exciting.”

Mr Hollingworth, who also works for the Science and Technology Facilities Council, is clearing away thousands of years of mud from the fossil before it is displayed at the water park’s visitor centre.

He said: “It is all the more remarkable considering Emily was using the type of spade children dig with at the seaside.”

Mr Baldry, who has been to one of the organised digs before, said he was delighted the water park will display his daughter’s find. “I’m glad that others will be able to see what Emily found,” he said.

“She did it all herself. We’re very proud of her.”

Emily is a Year One pupil at Monkton Park Primary School.

Her father, who works for Swedish company Transmode, said Emily’s mother Jessica was delighted when she her about her daughter’s find.

“I don’t think any of us realised exactly how exciting her find was until Neville saw what it was. We could hear in his voice how excited he was,” he said.

Although items found on organised digs at the water park are usually kept by the finder, Mr Baldry said he was pleased the fossil would be kept by the visitor centre.

“I have two young sons and the fossil is very heavy and has some spikes on it,” he said.

“It’s for the best that the water park keeps it.”