Dragon-like reptile sheds fresh light on rise of dinosaurs

By Mark Waghorn via SWNS

A dragon-like reptile dating back 233 million years has shed fresh light on the rise of the dinosaurs.

Scientists say it shows the evolution of the biggest animals that roamed land was even more complicated than previously believed.

The creature was more than four feet long from nose to tail with sharp, serrated teeth.

It lived during a period of high humidity and monsoons - preying on small vertebrates and insects.

The new species has been named Amanasaurus nesbitti - meaning "rain lizard."

It belonged to a group called silesaurs. Whether they were dinosaurs - or their direct ancestors - has been debated for years.

Lead author Dr. Rodrigo Muller, of The Federal University of Santa Maria, Rio Grande do Sul, in Brazil said: "According to our observations, Amanasaurus nesbitti was a primitive dinosaur.

"It was a member of the branch that triggered the armoured and horned dinosaurs - a lineage called Ornithischia."

They included Centosaurus, Pentaceratops - and iconic Triceratops.

Muller said: "The discovery helps explain the dinosaur origins puzzle. It is a new piece of the jigsaw."

Amanasaurus had a beak at the tip of its jaws to peck insects off the ground - somewhat like modern birds.

It was identified from the hind limbs of two individuals. The fossils were unearthed at a prehistoric animal graveyard in southern Brazil known as Restinga Seca.

Muller said: "This primitive dinosaur lived in landscapes adorned by ferns and large gymnosperms - flowerless plants that produce cones and seeds.

"It was a humid environment, marked by powerful rains. The neighborhood included a wide range of amphibians, reptiles and mammalian relatives.

"Among them, herrerasaurids dinosaurs were the most dangerous for Amanasaurus nesbitti.

"For instance, the herrerasaurid Gnathovorax cabreirai, a ten foot long carnivorous dinosaur with trenchant claws was excavated from a nearby outcrop."

Amanasaurus walked on four legs but ran on two. The palaeontologists excavated its remains of Amanasaurus from an area that has yielded several skeletons from distinct lineages.

This unexpected diversity from the dawn of the dinosaurs is comparable to that observed from 225 million year old beds - by which time they were well-established.

Muller said: "Whereas no skull remains where recovered for Amanasaurus nesbitti, its diet is inferred from its closest relatives, which are usually omnivorous.

"Some years ago, excrements of silesaurs from Poland were published. The fossilized poo, or coprolites, revealed the presence of insects.

"Moreover, the teeth of silesaurus also bear features usually related with the habit to consume vegetation.

"Amanasaurus nesbitti ingested plants, tiny vertebrates and insects."

The main dinosaur linages were emerging at this time - when South America was still part of the supercontinent Pangaea.

In response to novel and more adapted rivals, it has been suggested silesaurs were affected by competition - becoming smaller.

Muller said: "Amanasaurus indicates that the body size of silesaurs was not drastically affected. Actually, silesaurs and dinosaurs from other lineages reached similar body sizes."

The study also shows ecosystems that witnessed the early radiation of dinosaurs supported a wide diversity of dinosaurs and their relatives.

Muller said: "This challenges the idea 'archaic' reptiles were rapidly replaced by more evolved dinosaurs.

"Actually, the co-occurrence of silesaurs and other dinosaurs with similar body sizes within rich and diverse ecosystems indicates the origin of dinosaurs was much more complex than previously thought and that it was marked by an explosion of forms and species.

He added: "There are older silesaurs from Brazil - as well as Argentina, Tanzania and Zambia." It means Amanasaurus could put back the emergence of dinosaurs by millions of years.

At the outset they were less than 5ft long - and weighed about 14 pounds. Some later reached more than 130 feet - and 100 tons.

Amanasaurus is described in the journal Scientific Reports.