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A new species of sauropod – one of the first of its clade to roam Earth some 179 million years ago – has been unearthed in Argentina.
The “gentle giant”, called Bagualia alba, was about the size of a double-decker bus and had a sturdy skeleton, four stout legs, and a long neck for eating the leaves of tall trees.
Researchers believe it may have reached its gigantic size due to rapid global warming, caused by major volcanic eruptions in the southern hemisphere.
This has triggered drastic changes in the landscape, including an increase in the number of tall and evergreen conifers.
Bagualia alba was one of the few animals at the time with teeth strong enough to chew through the tough vegetation, making them the dominant species of herbivorous dinosaurs and perhaps explaining why they got so large.
B. alba was one of the earliest sauropods, a dinosaur clade that also includes Diplodocus, who lived about 25 million years later.
Sauropods were among the most voluminous creatures to ever walk the Earth, some weighing the equivalent of 14 African elephants.
Bagualia alba (depicted in the artist’s impression) was a “gentle giant” and 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, long-necked dinosaurs [and] like all sauropods it was herbivorous, “said Dr. Diego Pol of the Egidio Feruglio Paleontology Museum in Patagonia.
The bones are well preserved, including the fairly complete skull, which is very rare for a primitive sauropod because it is very delicate.
“Its teeth suggest that this dinosaur fed on conifers and other plants that made up the forests around 180 million years ago.”
Unlike the 130-foot, 100-ton-long beasts that later arrived in the sauropod ranks, B. alba was much smaller – around 40 feet from head to tail and weighed around 10 tons.
But the gentle giant’s impressive size would still have deterred carnivorous dinosaurs from attacking it.
More than 100 bones of at least three individuals of B. alba have been found, excavated from sediment layers in the Patagonian desert.
One 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 individuals of B. alba have been found, excavated from sediment layers in the Patagonian desert. The images show the reconstruction of the skull and neck of the species, including lateral (a) and posterior (b) skull views
Analysis indicated that the warm, humid climate in which the soft, lush vegetation had flourished suddenly vanished, to be replaced by more intense temperatures.
Warm, dry conditions arrived characterized by less varied flora, strongly dominated by conifers – woody cone-shaped seed plants.
‘These environmental changes were apparently caused by a greenhouse effect due to climate gases such as CO2 and methane caused by the increase in volcanism at that time,’ said Dr. Pol.
“Evidence of these eruptions is found on many southern continents, including South America, southern Africa and Antarctica.”
For the first 50 million years of their evolutionary history, Sauropodomorpha – the lineage to which sauropods belong – were represented by different groups of bipedal (those who walked on two legs) and quadrupeds (those who walked on all fours) animals.
Bagualia alba is a new Patagonian long-necked herbivorous dinosaur that retains a nearly complete skull. This species is 179 million years old and this age places it as one of the oldest true sauropods and marks the beginning of the dominance of giant long-necked dinosaurs in the Jurassic
Towards the end of the early Jurassic period (around 180 million years ago) the dinosaurs of the lineage to which sauropods belong suddenly disappeared and only one lineage survived and thrived: the great sauropods.
“What caused this fauna change during the early Jurassic had been puzzling so far, but this new radiometric dating shows that the rise of these dinosaurs coincided with the drastic environmental crisis,” said Dr.
With their thin teeth, the early small-bodied creatures preferred softer leaves and plants and thus became extinct due to the abundance of harder food.
“The large sauropods were the only lineage with much more robust dentition, well suited for such tough vegetation,” said Dr. Pol.
Thus they flourished and became the dominant group of herbivorous dinosaurs at that time.
“Indeed, the specialization for this type of vegetation was probably one of the reasons why these animals have reached their gigantic size.
“Because large digestion chambers are needed to cope with such foods, there was a general tendency for these animals to get bigger and bigger.”
Bagualia was also much larger and probably did not get attacked frequently once it reached adult size.
“It’s one of the evolutionary benefits that gigantism has benefited from in these herbivores,” said Dr. Pol.
At 179 million years B. alba is one of the oldest known sauropods and marks the beginning of the dominance of giant long-necked dinosaurs in the Jurassic, a period ranging from 201.3 million years ago to 145 million years ago.
The study was published in Proceedings of the Royal Society B: Biological Sciences.
SAUROPODS: LONG NECK AND SMALL BRAIN DINOSAURS
Sauropods were the first successful group of herbivorous dinosaurs, dominating most terrestrial ecosystems for over 140 million years, from the late Triassic to the late Cretaceous.
They had long necks and tails and relatively small skulls and brains.
They extended up to 130 feet (40 meters) and weighed up to 80 tons (80,000 kg), 14 times the weight of an African elephant.
Sauropods were the first successful group of herbivorous dinosaurs, dominating most terrestrial ecosystems for over 140 million years, from the Late Triassic to the Late Cretaceous
They were widespread: their remains were found on all continents except Antarctica.
They had their nostrils high on their skulls, instead of being at the tip of the snout like those of so many other terrestrial vertebrates.
Some fossils show that these nostril openings were so far in the skull that they were very close to the eye openings.
Sauropods such as Diplodocus began to diversify in the Middle Jurassic about 180 million years ago.
Source: University of California Museum of Paleontology
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