If you thought the 85ft-tall (25 metre) Diplodocus was big, think again.

Paleontologists recently unearthed a new species of тιтanosaur that would have measured a staggering 121ft-long (37 metres) when it roamed the Earth 102 million years ago.

The discovery was made in Argentina, and in a forthcoming documentary, naturalist Sir David Attenborough will tell the story of what led experts to make the amazing find.

Paleontologists recently unearthed a species of тιтanosaur (model shown right) that would have measured a staggering 121ft-long (37 metres) when it roamed Earth 102 million years ago. The discovery was made in Argentina, and in a forthcoming TV show, Sir David Attenborough (left) will tell the story of how it was found

The vegetarian тιтanosaur is thought to have been the biggest animal ever to have walked the Earth, weighing 70 metric tons – the equivalent of 14 African elephants.

Compared to a large Diplodocus – one of the most easily recognisable dinosaurs – the тιтanosaur was a whopping 36ft (11 metres) longer.

To put that into perspective, the prehistoric creature would have been the length of four double-decker buses.

In the documentary, due to air on BBC on 25 January, the famous broadcaster and naturalist will tell the tale of how in 2014, a shepherd spotted the tip of a gigantic fossil bone sticking out of a rock in La Flecha Farm in the Chubut Province in the Argentinian desert.

When the news reached palaeontologists at the Egidio Feruglio Palaeontology Museum (MEF) in Trelew, Argentina they set up camp at the discovery site.

In the documentary, due to air on BBC on 25 January, the famous broadcaster and naturalist will tell the tale of how in 2014, a shepherd spotted the tip of a gigantic fossil bone sticking out of a rock in the Argentinian desert. The excavation site is shown

Compared to a large Diplodocus, the тιтanosaur was a whopping 36ft (11 metres) longer. To put that into perspective, the prehistoric creature would have been the length of four double-decker buses. This graphic shows how Sir Attenborough would have looked stood next to the beast

The first bone turned out to be an 8ft-long (2.4metre) thigh bone – the largest ever found (shown left and right with Sir David Attenborough). By the end of the dig, the paleontologists had uncovered more than 220 bones and 80 teeth at the same site

Analysis of the leg bones show that the vast тιтanosaurs were young adults, but still growing. So the fully grown specimen would have been even bigger. This dinosaur is able to be much more accurately measured than Argentinosaurus (illustrated) was, because only a dozen of the latter’s bones were ever found

‘A comparison of the back bones shows that this animal was 10 per cent larger than Argentinosaurus, the previous record holder.

‘So we have discovered the largest dinosaur ever known.’

This dinosaur is able to be much more accurately measured than Argentinosaurus was, because only a dozen of the latter’s bones were ever found.

Filmed over two years, the documentary, called Attenborough and the Giant Dinosaur follows the twists and turns of this forensic investigation.

He witnesses the uncovering, cleaning and examination of these vast fossils for the first time.

Some of the fossils weigh over half a metric ton, so were hard to move from the remote location, some three hours from the nearest town.

Using state of the art graphics, the programme reveals what scientists think the internal structure of a dinosaur looked like and how it worked.

Using state of the art graphics, the programme will reveal what scientists think the internal structure of a dinosaur looked like and how it worked, as well as sH๏τs of the incredible bones (one pictured)

It explained that the animals’ heart would have weighed as much as three people and measured 6ft (two metres) in circumference.

It would have pushed up to 158 pints (90 litres) of blood round with one beat.

The тιтanosaur would have eaten a skip-full of food a day, using its huge gut to slowly digest its plant-based diet.

The documentary finishes with the unveiling of a mᴀssive skeleton built by a Canadian and Argentinian team of model makers, which represents the newly-discovered тιтanosaur.

It will air on BBC on Sunday January 24 at 6.30pm GMT.

The fossils were discovered at an excavation site in La Flecha Farm in the Chubut Province (shown) in the Argentinian desert

The new species of vegetarian тιтanosaur is thought to have been the biggest animal ever to have walked the Earth, weighing 70 metric tons, beating the previous record holder, fellow тιтanosaur Argentinosaurus. This stock image shows a boy looking at a 26ft-tall (eight metre) skeleton