Fossils of ‘first giant’ dinosaur uncovered in Argentina

Christopher Davidson
July 11, 2018

The discovery of the "first giant" dinosaur has provided a huge clue on how these paleo-beasts got to be the largest animals to walk on Earth.

The four-legged herbivore is three times the size of the largest dinosaur species discovered from the Triassic period to date. However, the newly discovered fossils show that, in fact, there is more than one way for gigantism to emerge in dinosaurs.

The find was published in the specialist Nature Ecology & Evolution journal on Monday and revealed in Argentina by the La Matanza National University's Scientific Dissemination Agency.

For most dinosaurs, gigantism proved to be an evolutionary survival tool, especially among herbivores who could use their size as a form of defence against predators.

Analysis showed that I. prima weighed between seven and 10 tonnes (the largest African elephants weight between six and seven tonnes), and it already exhibited an elongated neck and long tail, though not almost as pronounced as those seen later.

Together, these dinosaurs belong to a sauropod subgroup known as the lessemsaurids, which lived between 237 and 201 million years ago (relatively soon after dinosaurs first appeared) in what is now Argentina but was then the southeast corner of the supercontinent Pangaea.

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Until now, it was believed it emerged with the appearance of the first sauropods in the Jurassic period.

It had previously been thought that gigantism developed during the Jurassic period, around 180 million years ago.

Sauropods were the first successful group of herbivorous dinosaurs, dominating most terrestrial ecosystems for more than 140 million years, from the Late Triassic to Late Cretaceous.

It's believed that the species grew to eight to 10 meters (26-33 feet) tall - the specimen found was a growing youth measuring six to seven meters - and weighed around 10 tonnes, equal to two or three African elephants.

These adaptations included such things as small skulls, long necks and tails, column-like legs, rapid bone growth, and pneumatic vertebrae, where air spaces exist within the bones to make them light (a trait that still exists in modern birds).

Paleontologists made the discovery in Balde de Leyes, an area in western Argentina where other dinosaur species, as well as ancient turtles, iguanas and mice, were previously uncovered.

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