A 67 million-year-old Tyrannosaurus rex will go on sale in New York with a pre-sale value of $30m.

T. rex could become most expensive fossil ever - but it's a ​problem for scientists In 1997, Sotheby's hosted its first natural history auction selling fossils and other wonders of our prehistoric world. It was a niche event mostly attended by the world's museums looking for specimens to add to their collections. On the books that day was a Tyrannosaurus Rex called Sue - she was eventually sold for $8m (£6m) to the Field Museum in Chicago. Nearly 30 years later, on Tuesday, another T. rex will make an appearance at the annual auction - one of the most complete specimens of this kind ever found. And this time it is not just scientists who are dinosaur-hunting but also the super-rich. The new specimen, known as Gus, has already been valued at $30m but it could fetch more, possibly even becoming the most expensive dinosaur ever sold. It adds to a growing debate in the natural history world – should specimens of such scientific importance be reserved for museums and their scientists?