A new species of sauropod – one of the earliest of its clade to ever roam the Earth around 179 million years ago – has been unearthed in Argentina.
The 'gentle giant', named Bagualia alba, was about the size of a double-decker bus and had a robust skeleton, four sturdy legs and a long neck for eating leaves off tall trees.
Researchers believe that it may have reached its gigantic size due to rapid global warming, caused by major volcanic eruptions in the southern hemisphere.
This triggered drastic changes in the landscape, including an increase in the number of tall, evergreen conifers.
Bagualia alba was one of the few animals at the time with strong enough teeth to chew through the tough vegetation, resulting in them becoming the dominant species of herbivorous dinosaurs, and possibly explaining why they grew so big.
B. alba was an early sauropod – a clade of dinosaurs that also includes Diplodocus, which lived around 25 million years later.
Sauropods were among the bulkiest creatures to have ever walked the Earth, some weighing the equivalent of 14 African elephants.
Bagualia alba (pictured in artist's impression) was a 'gentle giant' and a herbivore, just like all sauropods
B. alba is the oldest known eusauropod (a type of sauropod) and one of the oldest known sauropods.
'Bagualia is a sauropod – the large bodied, quadrupedal and long necked dinosaurs [and] like all sauropods it was herbivorous,' said Dr Diego Pol of The Museum of Palaeontology Egidio Feruglio in Patagonia.
'The bones are beautifully preserved including the fairly complete skull, which is very very rare for an early sauropod because they were very delicate.
'Its dentition suggests this dinosaur fed on the conifers and other plants that composed the forests about 180 million years ago.'
Unlike the 130 foot-long, 100-ton beasts that came later in the sauropod lineup, B. alba was much smaller – about 40 feet from head to tail and weighing about 10 tons.
But the gentle giant's impressive dimensions still would have deterred carnivorous dinosaurs from attacking it.
More than 100 bones of at least three B. alba individuals were found, dug up from layers of sediment in the Patagonian desert.
An analysis calculated the age of the rocks using a technique called radiometric dating, based on the decay rate of certain chemicals.
More than 100 bones of at least three B. alba individuals were found, dug up from layers of sediment in the Patagonian desert. Images show the skull and neck reconstruction of the species, including skull side view (a) and back (b)
The analysis indicated the warm and humid weather in which soft and lush vegetation had thrived vanished suddenly, to be replaced by more intense temperatures.
Hot and dry conditions arrived that were characterised by less varied flora, heavily dominated by conifers – woody, cone-bearing seed plants.
'These environmental changes were apparently driven by a greenhouse effect due to climate gasses such as CO2 and methane caused by increased volcanism at that time,' said Dr Pol.
'Evidence of these eruptions are found on many southern