Bigger than the biggest dinosaurs of the Triassic

A text of Alain Labelle

The first fossilized remains of the baptized species Ingenia prima were discovered in 2015 on the paleontological site of Balde de Leyes, in the province of San Juan, 1100 kilometers west of Buenos Aires

Since then, vertebrae of the neck and tail, bones of the front paws and part of the bones of the hind legs have been uncovered.

This is a quadruped herbivorous dinosaur that is easily distinguished by its long neck and long tail

This specimen measured 6 to 7 meters, was young and weighed about 10 tons, or the weight of 2 to 3 elephants.

Ingenia prima was almost three times the size of the largest dinosaurs of the Tribadic period (from -251 to -200 million years ago)

The appearance of gigantism reviewed

Dinosaurs dominated terrestrial ecosystems p more than 140 million years ago during the Mesozoic (a geological era extending from -252 to -66 million years).

Among them were the sauropodomorphs, which include the clone of sauropods, the most large animals treading on the ground according to the present state of our knowledge, but also more primitive forms of smaller bipeds.

Paleontologists have long thought that the acquisition of a giant body in this clade (over 10 tons) occurred during the Jurbadic and that it was linked to many skeletal changes in sauropod dinosaurs

Although the origin of gigantism in sauropodomorphs represents a pivotal stage in the evolution of dinosaurs, there were as yet few fossils to understand this evolutionary change crucial.

An important link

In the present works, the scientist Cecilia Apaldetti and her colleagues from the Institute and Museum of Natural Sciences of the University of San Juan (IMCN) describe a new sauropodomorph who lived in the Upper Tribadic in southwestern Pangea, the supercontinent that began to break up in the Tribadic.

As soon as it was found, I thought it was something different. We discovered a shape, the first to be giant in the middle of all dinosaurs. This is the novelty

The members of this clade have reached a large size while maintaining a pattern of cyclic growth, with many characteristics of the body plan of the first sauropodomorphs and devoid of most anatomical features previously considered as adaptations to gigantism.

This adaptive strategy shows a highly accelerated growth rate, an avian-style respiratory system, modifications of the vertebral musculature, but also hind limbs essential to the evolution towards gigantism

The description of this new specimen is thus a first impulse towards gigantism in dinosaurs that would have occurred more than 30 million years before the appearance of the first eusauropods, a clone of sauropod dinosaurs gathering all the sauropods more close to titanosaurs like the Saltasau rus .

Until today, paleontologists have estimated that the gigantism of dinosaurs first appeared in the Jurbadic period about 180 million years ago.

The details of this work is published in the journal Nature Ecology & Evolution.