The Natural History Museum is embarking on its first major overseas dig since the 1980s in the hope of unearthing new Jurassic-era dinosaurs.

The project, entitled Mission Jurassic, which will excavate a square mile of land in Wyoming, US, will involve a team from the Natural History Museum working alongside scientists from the Children’s Museum of Indianapolis and the Naturalis Biodiversity Center in Leiden, Netherlands.

The dig will begin this summer, but initial excavations have already uncovered the bones of two giant dinosaurs, which appear to belong to a 24-metre-long brachiosaurus and 30-metre-long diplodocus. Nearly 600 fossilised bones, weighing nearly 5.4 tonnes, have been collected over the past two years of preliminary fieldwork, although only a fraction of the site has been explored. The region, known as the Jurassic Mile, is known to be rich in Jurassic dinosaur and fish fossils, trackways and fossilised plants, of up to 150m years old.

Prof Paul Barrett, senior dinosaur specialist at the Natural History Museum, said: “This is the time when we get a lot of iconic dinosaurs, like brachiosaurus, diplodocus and stegosaurus. One of the reasons it’s exciting is that this set of rocks has been much less extensively explored for fossils [than other areas in the US]. There are some indications that there are different dinosaurs there.”

Barrett said the discovery of a new brachiosaurus specimen would be particularly exciting because most existing fossils are fragmentary. To completely excavate a large dinosaur fossil – brachiosaurus could grow to 25 metres long and 13 metres tall – would probably take a couple of years, Barrett said.