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A new study suggests that long-necked sauropods, the largest animals walking the Earth, may have dominated during the Jurassic period thanks to a large explosion of volcanic activity that began around 184 million years ago. The resulting environmental crisis could cause a change in plant life that gave hard-toothed, large herbivores a powerful advantage over other herbivores.
The discovery derives from the discovery of a new fossil of one of the first “real” sauropods in Argentine Patagonia. The sediments bearing the recently described dinosaur, nicknamed Bagualia alba, date back precisely to 179 million years ago, paleontologist Diego Pol of the Egidio Feruglio Paleontological Museum in Trelew, Argentina and colleagues report November 18 in Proceedings of the Royal Society B.
B. alba, the researchers found, had the telltale characteristics of true sauropods: legs wide, like columns; huge size; long necks in relation to the body; wide and strong jaws; and large spoon-shaped teeth with thick enamel. Also known as eusauropods, this lineage dominated the Middle and Late Jurassic from about 174 to 145 million years ago (SN: 10/10/07), giving rise to impressive giants such as Argentinosaurus and Dreadnoughtus schrani (SN: 6/9/15). ).
During the early Jurassic period, about 201-174 million years ago, Pol says, plant-eating sauropods competed with many other herbivores, including sauropodomorphs, distant relatives such as Mussaurus patagonicus with less powerful jaws and shorter necks (SN: 5). / 20/19). It has not been clear what the eusauropod giants gave in their herbivorous competition, in part because there are relatively few fossils dating back to the transition between the Lower and Middle Jurassic.
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One possible culprit was an environmental crisis that occurred in the late Lower Jurassic, an episode of global warming and ocean acidification that led to the extinction of numerous species, particularly in the oceans but also on land. Scientists have previously suggested that this episode was related to large volcanic eruptions in the southern hemisphere.
That volcanic surge may also have led to a major shift in plant life in the region. The early Jurassic was dominated by seed ferns, cycads, and ginkgoes, but by the Middle Jurassic conifers began to flower in the drier, warmer climate. This, in turn, may have made life difficult for many sauropodomorphs, who disappeared from fossils after the Lower Jurassic.
But B. alba, the study shows, was alive and well 179 million years ago, well after the aftermath of the volcano. Pol and his colleagues suggest that B. alba and other eusauropods may have been in a better position to prick the very hard leaves of conifers. Pol and his colleagues said that his extra powerful jaws and teeth could chew on those leaves, and his oversized guts were well suited to digest hard plant matter, allowing him to sit and ferment for many days.
Careful dating of the new fossil is a crucial piece of the puzzle, Pol says, because “it provides the first accurate evidence (that) large sauropods became the dominant herbivores in terrestrial ecosystems soon after the massive volcanic event.”
The Bagualia alba tooth, discovered in Argentine Patagonia, has the typical spoon shape and thick enamel of sauropods. These features helped the creatures to bite the hard leaves of conifers, which bloomed after about 180 million years ago. New research suggests that this ability may have allowed sauropods to become dominant in the Jurassic period.Santiago Reuil
The new fossil “is an important complement to our frustrating and incomplete picture of the evolution of early sauropods,” says Paul Barrett, paleontologist at the Natural History Museum in London. And the coincidence between the fossil age and a significant surge of volcanic activity in the region is intriguing, he adds.
But, he says, “I’d like to see a little more evidence before extending it to a global event” that has led to changes in the evolution of both plants and dinosaurs. Although this is the first true sauropod fossil found, the lineage of sauropods is thought to date back another 40 million years, to the late Triassic, based on analyzes of the animal’s family tree. And scientists know very little about how those early sauropods fed, not even where they lived in the world. For example, it is possible that the first true sauropods lived in places where such climatic and floral changes did not occur.
For now, though, “the authors offer a new and interesting idea that we can test with new findings in the future,” says Barrett. “If they are right, this would give a good insight into the understanding of the links between the evolution of the planet, climate, flora and fauna.”
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