Three skeletons of an entirely new species of dinosaur have been unearthed in Brazil. Standing on hind legs but with incredibly long necks and tails, the creatures look like a strange mashup between multiple dinosaur species. But excitingly, their odd appearances show evolution in action, shedding new light on how the giant, long-necked dinosaurs known as sauropods came to be.

Living over 225 million years ago, the newly named Macrocollum itaquii is the oldest long-necked dinosaur ever found. It was about 3.6 meters (12 feet) long, 1.5 meters (5 feet) tall, and weighed 100 kilograms (220 pounds). It existed before supersized dinosaurs first appeared on Earth.

Its discoverers, who describe the species in the journal Biology Letters, note that their dinosaur was no man-eater. Analysis of its teeth suggests that it was veggie through and through. As plants aren’t quite as nutritious as meat, it would have had to chow down on a lot of flora to nourish its large body, and this is where its bizarrely long neck comes in. M. itaquii’s neck would have enabled it to reach more vegetation, just like giraffes' necks do today. 

"It would have allowed members of the group to reach higher vegetation compared to other early vertebrates,” lead author Rodrigo Müller of the Federal University of Santa Maria in Brazil told The Independent.

One particularly exciting feature of the discovery is that it involved three skeletons, not one. This suggests that the species was social, not solitary, even at a pretty early point in dinosaur evolution – dinosaurs first appeared around 240 million years ago. The authors note that this is the oldest evidence of social behavior in the sauropodomorphs, the clade of dinosaurs that includes the sauropods and their ancestors.

"There are three articulated skeletons in 5 tons of rock,” explained Müller. "This is unique. It suggests these animals probably died together, as they share the same degree of disarticulation. So if they died together, these dinosaurs probably lived together.”

M. itaquii marks a transitional point in sauropodomorph evolution, as it had developed a long neck and vegetarian diet but was still fairly small and walked upright on two strong hind legs.

"The new species allows the definition of a set of anatomical changes that shaped sauropodomorph evolution along a period from 233 to 225 million years ago,” the authors noted in their paper. "In that time span, apart from achieving a more herbivorous diet, sauropodomorph dinosaurs increased their size in a ratio of 230 percent and their typical long neck was also established." 

Sauropodomorphs that arose later were enormous and walked on all four legs – think of the titanosaurs, which grew to 37 meters (122 feet) in length and weighed 70 tonnes (77 tons). This clade of dinosaurs were true Goliaths of the Jurassic world.