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Palaeontologists are referring to Chilesaurus diegosuarezi (illustrated) as a 'platypus' dinosaur because of its bizarre combination of features

A new lineage of dinosaur that grazed on plants, despite being closely related to notorious carnivore Tyrannosaurus rex, has been discovered in Chile.

Palaeontologists are referring to Chilesaurus diegosuarezi as a 'platypus' dinosaur because of its bizarre combination of characteristics, including its small skull and feet. 

These features are more like those seen on long-neck dinosaurs.

The animal is proving to be an evolutionary jigsaw puzzle because it belongs to the theropod group of dinosaurs - which includes the famous meat eaters Velociraptor, Carnotaurus and Tyrannosaurus, from which birds today evolved - but was a vegetarian.

The presence of herbivorous theropods was up until now only known in close relatives of birds, but Chilesaurus shows that a meat-free diet was acquired much earlier than first thought.

The dinosaur from the Late Jurassic Period, around 145 million years ago, is named after the country where it was discovered, as well as honouring Diego Suárez, who discovered the bones.

The seven-year-old came across the fossils at the Toqui Formation in southern Chile when he and his sister, Macarena were looking for decorative stones.

They were playing at the site because their geologist parents, Manuel Suarez and Rita de la Cruz were studying rocks with the aim to better understand the formation of the Andes mountain range.

Experts initially thought Diego had unearthed several species, due to Chilesaurus' unusual combination of features.

However, more than a dozen specimens have now been excavated, including four skeletons, which demonstrate that the dinosaur combined a variety of unique anatomical traits. 

The dinosaur has been likened to a platypus, which is one of the most unusual creatures in the animal kingdom, because it's one of very few mammal to lay eggs, has venomous spurs and a paddle-shaped tail like a beaver, as well as webbed feet and a bill like a duck, among other idiosyncrasies. 

Most of the specimens discovered are the size of a turkey, but some isolated bones reveal the maximum size of Chilesaurus was around 10 feet (three metres) long, according to Chilean and Argentinian palaeontologists from institutions including the University of Birmingham who have studied the skeletons.

Unusual: Fossils dating from the Late Jurassic Period, around 145 million years ago, reveal an unusual combination of features from various dinosaur groups, including relatively short arms, a long neck, small head and leaf-shaped teeth (pictured)

Bizarre: Palaeontologists are referring to Chilesaurus diegosuarezi as a 'platypus' dinosaur because of its bizarre combination of characteristics including its small skull and feet, which are more like those seen on long-neck dinosaurs. The dinosaur itself, has a lengthy neck and must have had good balance (illustrated)

They discovered that Chilesaurus has robust forelimbs similar to Jurassic theropods such as Allosaurus. 

But its hands have two blunt fingers, instead of sharp claws like its fellow theropod the Velociraptor.

Chilesaurus' pelvic girdle resembles that of the ornithischian dinosaurs - beaked, herbivorous dinosaurs such as stegosaurs and Iguanadon - whereas it is actually classified in the other basic dinosaur division – Saurischia, according to the study published in the journal Nature.

The different parts of the body of Chilesaurus were adapted to a particular diet and way of life, which was similar to other groups of dinosaurs.

As a result of these habits, different regions of the body of Chilesaurus evolved resembling those present in other, unrelated groups of dinosaurs - a phenomenon called evolutionary convergence.

Chilesaurus represents one of the most extreme cases of evolutionary convergence.

For example, its leaf-shaped teeth are similar to those of primitive long-neck dinosaurs because they were selected over millions of years as a result of a similar diet between these two lineages of dinosaurs.

'Chilesaurus can be considered a "platypus" dinosaur because different parts of its body resemble those of other dinosaur groups due to mosaic convergent evolution,' Martín Ezcurra, a researcher at the University of Birmingham explained.

Painstaking: Close inspection of the fossils revealed that Chilesaurus has robust forelimbs similar to Jurassic theropods such as Allosaurus. But its hands have two blunt fingers, instead of sharp claws like its fellow theropod, the Velociraptor. The process of excavating the skeleton is shown 

The presence of herbivorous theropods was, up until now, only known in close relatives of birds but Chilesaurus (illustrated left) shows that a meat-free diet was acquired much earlier than thought. Its fossils were found at the Toqui Formation in southern Chile, marked with a red star on the map, right

'In this process, a region or regions of an organism resemble others of unrelated species because of a similar mode of life and evolutionary pressures.

'Chilesaurus provides a good example of how evolution works in deep time and it is one of the most interesting cases of convergent evolution documented in the history of life. 

'Chilesaurus shows how much data is still completely unknown about the early diversification of major dinosaur groups.' 

He believes that this study will force palaeontologists to take more care in identifying fragmented and isolated dinosaur bones.

Dr Fernando Novas, of the Bernardino Rivadavia Natural Sciences Museum in Buenos Aires, Argentina, led the research on Chilesaurus.

Seven-year-old Diego Suárez (pictured left) came across the fossils when he and his sister, Macarena, were looking for decorative stones. He was at the site while his his geologist parents, Manuel Suarez (pictured right) and Rita de la Cruz were studying rocks with the aim to better understand the formation of the Andes

Experts initially thought Diego had unearthed several species, due to Chilesaurus' unusual combination of features. Here, a palaeontologist painstakingly excavates the fossils

He said: 'Chilesaurus is the first complete dinosaur from the Jurassic Period found in Chile and represents one of the most complete and anatomically correct documented theropod dinosaurs from the southern hemisphere.

'Although plant-eating theropods have been recorded in North America and Asia, this is the first time a theropod with this characteristic has been found in a southern landmass.

'Chilesaurus was an odd plant-eating dinosaur only to be found in Chile.

'However, the recurrent discovery in beds of the Toqui Formation of its bones and skeletons clearly demonstrates that Chilesaurus was, by far, the most abundant dinosaur in southwest Patagonia 145 million years ago.'

HOW DINOSAURS SHRANK OVER 50 MILLION YEARS 

The lineage of huge meat-eating dinosaurs that transformed into agile flying birds were able to survive because they shrank over the course of 50 million years.

This is the conclusion scientists came to after constructing a detailed family tree of dinosaurs and their bird descendants, mapping the unlikely transformation.

The tree showed that the branch of theropod dinosaurs, which gave rise to modern birds, were the only dinosaurs that kept getting smaller.

The lineage of huge meat-eating dinosaurs that transformed into agile flying birds were able to survive because they shrank over 50 million years. This is the conclusion scientists came to after constructing a detailed family tree of dinosaurs and their bird descendants, mapping their unlikely transformation

Theropods, meaning 'beast-footed', were a group of dinosaurs which include the carnivorous dinosaurs Tyrannosaurus, Velociraptor and Spinosaurus.

'These bird ancestors also evolved new adaptations, such as feathers, wishbones and wings, four times faster than other dinosaurs,' said co-author Darren Naish, a palaeontologist at the University of Southampton.

Lead author Associate Professor Michael Lee, from the University of Adelaide, said: 'Birds evolved through a unique phase of sustained miniaturisation in dinosaurs.'

'Being smaller and lighter in the land of giants, with rapidly evolving anatomical adaptations, provided these bird ancestors with new ecological opportunities, such as the ability to climb trees, glide and fly.

'Ultimately, this evolutionary flexibility helped birds survive the deadly meteorite impact which killed off all their dinosaurian cousins.'

Researchers examined over 1,500 anatomical traits of dinosaurs to reconstruct their family tree.

They used mathematical modelling to trace evolving adaptions and changing body size over time and across dinosaur branches.