Carnivorous dinosaur turns vegetarian

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Killer dino 'turned vegetarian'

 

The creature provides a " missing link " in dinosaur evolution

 

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The " mass graveyard " of a bird-like dinosaur has been uncovered in

Utah, US, Nature magazine reports this week.

 

Scientists believe the previously unknown species was in the process

of converting to vegetarianism from a rather more bloodthirsty diet.

 

Falcarius utahensis seems to represent an intermediate stage between a

carnivorous and herbivorous form.

 

The creature, which lived about 125 million years ago, provides a

" missing link " in dinosaur evolution.

 

" Falcarius represents evolution caught in the act, a primitive form

that shares much in common with its carnivorous kin, while possessing

a variety of features demonstrating that it had embarked on the path

toward more advanced plant-eating forms, " said co-author Scott

Sampson, of the Utah Museum of Natural History.

 

 

This little beast is the missing link between predatory dinosaurs and

the bizarre plant-eating therizinosaurs

Scott Sampson, Utah Museum of Natural History.

Falcarius utahensis belonged to a group of dinosaurs known as

therizinosaurs, which were cousins of Velociraptor dinos and the early

ancestors of birds.

 

The bizarre creature appears to sit halfway between nippy carnivores

and later, lumbering plant-eating therizinosaurs, although scientists

cannot be entirely sure what it ate itself.

 

" Falcarius shows the beginning of features we associate with

plant-eating dinosaurs, including a reduction in size of meat-cutting

teeth to leaf-shredding teeth, the expansion of the gut to a size

needed to ferment plants and the early stages of changing the legs so

they could carry a bulky body instead of running fast after prey, "

said James Kirkland, of the Utah Geological Survey.

 

Ferocious past

 

The adult dinosaur walked on two legs, was about 4m long (13ft) and

stood 1.4m tall (4.5ft). It also had a woolly feather-like plumage and

sharp, curved 10cm-long (4-inch) claws.

 

These formidable talons were probably a hang-over from the dinosaur's

ferocious past, the researchers say, and may not have had a function

in its more sedate new lifestyle.

 

Falcarius shared an - as yet undiscovered - ancestor with the

Velociraptor, which was almost certainly a fleet-footed, small-bodied

predator, the researchers believe.

 

At some point, two major groups of dinosaurs split from their

carnivorous cousins and shifted into plant-eating. But until now, the

intermediate stages of this process remained a mystery.

 

" With Falcarius, we have actual fossil evidence of a major dietary

shift, certainly the best example documented among dinosaurs, " said Dr

Sampson.

 

" This little beast is the missing link between small-bodied predatory

dinosaurs and the highly specialised and bizarre plant-eating

therizinosaurs. "

 

Mass grave

 

Although the team cannot know whether Falcarius was a committed

vegetarian - it may have eaten a bit of meat, too - its emergence did

coincide neatly with the evolution of flowering plants.

 

" At the same time Falcarius appeared, the world was changing greatly

because flowering plants were appearing, " Dr Sampson said. " They would

have provided a new food source. It could be that Falcarius was

exploiting an open ecological niche. "

 

A model of Falcarius utahensis, copyright PaleoForms LLC

Its formidable talons were probably a hang-over from the dinosaur's

more ferocious past

Researchers were able to get such a complete idea of what Falcarius

looked like, because they were lucky enough to find a " mass grave " of

the species at the base of the Cedar Mountain rock formation, south of

Green River in Utah.

 

James Kirkland estimates hundreds to thousands of individual dinosaurs

- from hatchlings to adults - died at the 8,000 sq m dig site.

 

No one knows quite what killed them, but mass deaths have appeared in

the fossil record before. Scientists have suggested drought,

volcanism, fire and botulism poisoning as possible causes.

 

" Mass mortalities are known in a number of dinosaur groups, " said Dr

Sampson. " In this case, it is difficult to work out what happened. It

could have been a spring which dried up, and the dinosaurs died of thirst.

 

" Or organic poisons could have contaminated the water - it is hard to

know for sure. "