(38m) in length. It existed 90 million years ago, when the great Andes were hillocks and the arid badlands of North Patagonia a swathe of steamy jungle and lush savannah grassland.

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On the outskirts of a second, nearby town, scientists unearthed the skeleton of Giganotosaurus Carolinii, a ferocious carnivore and predator of Argentinosaurus. Giganotosaurus was, according to palaeontologist Dr. Jorge Calvo, a terrifying spectacle: a 10-ton meat-eater that was 46ft (14m) long, 23ft (7m) tall and three tons heavier than North America's bad boy Tyrannosaurus Rex. Giganotosaurus hunted Argentinosaurus in packs, stalking and felling the giant leaf-eater on the open savannah before ripping its flesh apart with serrated teeth eight inches long - teeth which protruded from a skull bigger in size than a modern-day bathtub. Dr. Calvo has a liking for metaphor.
The dinosaur route in northwest Patagonia is a marvellous adventure.  The skeletons of the biggest dinosaurs ever to have walked the planet are, palaeontologists insist, buried in this region's red-rock badlands; and discoveries to date in the area have forced scientists to rethink established theories of dinosaur size and behaviour.
The fossilized skeleton of Giganotosaurus is housed at the dinosaur museum at Villa El Chocón. Villa El Chocón is a small town set on the shore of a beautiful artificial lake. It comprises a few rows of identical houses, built to house the workers of a hydro-electrical dam and a brief line of shops. It has an air of non-description, but its museum is a marvel. Inside the museum, the fossilized skeleton of Giganotosaurus lies flat on a sandy bed. It is an astonishing 80% intact.
On the outskirts of Villa El Chocón, sticking to the lakeshore, you can see the footprints of another prehistoric giant, Iguanadon, imprinted on the shore. Iguanadon was a bulky herbivore that had conical spikes instead of thumbs, used for defence against predators. It deposited its gigantic footprints here some 120 million years ago and they remain perfectly preserved.
A third site, Lago Barreales is a sapphire lake wrapped within scenery of red and orange rock faces. On the lake's northern shore, a fossil of a giant femur bone, bigger than an adult man, leans against a rock-face and signals your arrival at the Lago Barreales Paleontological Center. The femur belongs to Futalognkosaurus, an enormous leaf-eater discovered at this spot. It rivalled Argentinosaurus for size and had a powerful tail, which it used to swat away predators. Dr. Calvo is chief palaeontologist at Lago Barreales.
Lago Barreales is unique in Latin America palaeontology in that it is an excavation site that receives overnight guests - albeit in rustic trailers (which only add to the awesome sense of adventure). Its guests - called sponsors by Centre staff - enjoy the rare opportunity of joining palaeontologists in the field. Just four sponsors at a time are permitted to stay, and you get to play Indy Jones in the desert.
It is full immersion. Under a desert sun, to a backdrop of the Andes Mountains, scientists teach sponsors to read a landscape that is 100 million years old and to recognize, via texture and colour, fossils in the prehistoric rock. Sponsors participate at every stage of the paleontological process, side-by-side with a site scientist: from the use of hammer and chisel to free fossils from hard rock, to the moulding of bone replicas for display at the on-site laboratory. Mealtimes are spent with Centre staff, most often Argentinean asado under the Patagonian stars.
Dr. Calvo, who pioneers paleontological tourism in Latin America, says: "Our aim is that sponsors really get to feel part of the team... that after two days every sponsor really feels as if he or she is a palaeontologist."
Staff at Lago Barreales drives travellers across red-rock country to Patagonia's other dino hotspots, Villa El Chocón and Plaza Huincul, both nearby. Plaza Huincul is a gloomy oil town with a reputation for political protest, but its paleontological museum exhibits the partial skeleton of the biggest dinosaur ever to thunder across Earth. The vertebrae alone of Argentinosaurus measure 5ft (1.5m) in height. It is a spine-tingling spectacle.