Fossils of Ingentia prima - ‘the first giant’

Christopher Davidson
July 14, 2018

But here it is.

Reconstruction of Ingentia prima.

Research published this week in Nature Ecology & Evolution outlines an early trend towards gigantism in Triassic dinosaurs, centring on the fossil of Ingentia prima.

All this, according to Apalette, says that the first giant dinosaurs appeared on Earth at least 30 million years earlier than paleontologists believed in the past.

Artist's illustration of the newfound dinosaur.

The paleontologist, who wasn't involved in the new study named, Steve Brusatte, said in an email, "This is a really unexpected new discovery, and I think it is one of the most important new dinosaurs of the past few years".

Initially, scientists thought that huge dinosaurs evolved in a very specific way.

At about 23-33 feet (7-10 m) in length and approximately 10 tons in weight, it was about three times the size of the largest Triassic dinosaurs.

Ingentia throws a wrench into that model of giant dino evolution.

Large size, scientists believe they began to be achieved only in the middle and at the end of the Jurassic period, about 180-155 million years ago, when the first neosauropods, including Diplodocus, argentinosaurus and all of the largest dinosaurs of that era.

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Cyclical growth was common in the growth of primitive sauropods in the Triassic period (between 251 and 199 million years ago), but no dinosaur of this type ever exceeded two or three tonnes. "Since almost all later sauropods have this basic body plan, discovering animals that hint at how and when such a plan first evolved is exciting", Curry Rogers, who wasn't involved in the new study, added.

According to scientists, Ingenia prima was the first dinosaur species to reach gigantism and even though it was a long way from the 70 tonnes (tons) that the biggest sauropods weighed from the end of the Cretaceous period (145-66 million years ago), the speed of bone tissue accumulation was greater than that of species from its era and the biggest giants that lived in Patagonia, in the south of Argentina.

These were "herbivore dinosaurs, quadrupeds, easily recognisable by their very long neck and tail, and from the sauropod group", she added. "But Ingentia prima lived during the last part of the Triassic period, between 210 and 205 million years ago".

"When we found the first remains of this dinosaur, we realized he was unique".

In 2015, Apaldetti and her colleagues discovered the new species while looking for Triassic Period fossils in northwest Argentina.

"In the same way that you see in a tree, where you can recognise seasons of growth linked to climatic or environmental factors, in the bone cuttings carried out in Ingentia Prima we discovered a cyclic, seasonal growth", he said, quoted in the UNSJ online magazine.

The findings suggest there might be more lessemsaurids yet to be discovered that we don't know about. "So, the lessemsaurids force us to rethink when, why, and how some dinosaurs got so monstrous".

And the truth is, there may be no reason for the gigantism at all.

Curry Rogers said "Who knows what the objective of developing large body shapes can be - usually things develop from the spot, but the environment is sufficiently adequate to work and the organisms are spun into the population".

"But, sometimes being larger can be a helpful defense against predators - and growing fast to gain that bigger body size makes it possible to outpace those things in your ecosystem that might try and eat you if you stay small for a long time".

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