A remote canyon in Death Valley has been kept shielded from the public for the past 76 years, to preserve a huge cache of fossilised animal tracks.

The collection of prints is one of the biggest, most diverse and well-preserved in the world.

Now palaeontologists, who refer to the secret canyon as 'The Barnyard', have called for the US National Park Service to open up the area to the public.

Loma Linda University palaeontologist Torrey Nyborg admires the fossil tracks of a cat the size of a leopard that prowled the mud around a watering hole about 5 million years ago

THE ANCIENT TRACKS The ancient tracks, which were left over time in successive layers of mud, range in size from around 1 inch (2.54cm) to 15 inches (38.1cm) in length. They were left by ancient camels, horses, big cats, birds, tapirs and elephant-like mastodons. The fossils were set in mud lining the shores of a lake, a popular spot for migrating mammals and birds. Advertisement

The remote area in the Death Valley National Park, which straddles the border between California and Nevada, features fossils tracks left by ancient camels, horses, big cats, birds, tapirs and elephant-like mastodons.

It has been kept off limits since 1940 and officials ask that its exact location is not divulged.

The Park itself receives around a million visitors every year.

The oldest of the tracks are thought to date back as far as 5 million years.

'This canyon is as good as it gets — there are fossil tracks almost everywhere you look,' Torrey Nyborg, a Loma Linda University paleontologist told Louis Sahagun of the Los Angeles Times.

Mr Nyborg recently completed an extensive inventory of the track and is working with the National Park Service to preserve them from the elements and protect them from vandalism.

Naturalist Birgitta Jansen, from left, Death Valley National Park Ranger Abby Wines and Loma Linda University paleontologist Torrey Nyborg in the heart of a canyon

Visitors to the fossil-laden canyon are currently required to have a permit and be accompanied by an official.

Only around 100 people are permitted to enter the area each year, reports the LA Times.

The ancient tracks, which were left over time in successive layers of mud, range in size from around 1 inch (2.54cm) to 15 inches (38.1cm) in length.

Loma Linda University palaeontologist Torrey Nyborg (far left), naturalist Birgitta Jansen (middle), and Death Valley National Park Ranger Abby Wines (seated on the right) in the remote canyon

The remote area in the Death Valley National Park, which straddles the border between California and Nevada, features fossils tracks left by ancient camels, horses, big cats, birds, tapirs and elephant-like mastodons. Its exact location is a closely guarded secret

Loma Linda University palaeontologist Torrey Nyborg (pictured) believes that that secret canyon should be opened up to the public in future (Louis Sahagun/Los Angeles Times/TNS)

The fossils were set in mud lining the shores of a lake, a popular spot for migrating mammals and birds.

The Death Valley National Park stretches over 5,270 square miles (13,650 km) of land, while the tracks cover an area of around five square miles (12.9 square km)

The fossilised tracks took four years to catalogue.

'This canyon has been in the dark too long; I want to see it unveiled to the world,' Mr Nyborg told the LA Times.

He believes that the preservation of the area will rely on public support for a comprehensive maintenance initiative.

Last week, the Death Valley National Park ran a series of drop-in days for volunteers to help clean and maintain the park.

The National Park Service is celebrating its centennial year, marking the day on 25 August 1916 when President Woodrow Wilson signed the Act that led to its creation.