Dinosaur heart found

The heart: A a grapefruit-sized, reddish brown clump

The first ever fossilised dinosaur heart has been discovered by scientists in the US.

This means that dinosaurs, certainly the later ones, were probably warm-blooded and engaged in active behaviour

Dr Dale Russell

It was found in the remains of a 66 million-year-old creature dug up in South Dakota.

The researchers used a computer tomography (CT) scanner to investigate the organ. The study shows the dinosaur, nicknamed "Willo", to have a four-chambered heart more akin to a human or a bird than a lizard.

The findings, the scientists claim, suggest the beast's circulatory system was more advanced than that of reptiles, and supports the hypothesis that many dinosaurs were warm-blooded animals.

Extraordinary secret

Willo was discovered in a sandstone outcrop in 1993, and named after the wife of the rancher who owned the land.

2-D images were built into a 3-D model

The 300-kilogram (663-pound), four-metre (13-foot) long herbivore was acquired by the North Carolina Museum of Natural Sciences, Raleigh, in 1996, where he is now on permanent display. However, it is only in the last few months that scientists from the state university's college of veterinary medicine have been able to reveal the fossil's extraordinary secret.

CT scans use X-rays and computer software to "peel away" layers of tissue, or in this case layers of dirt and fossilised bone, to image inside a body.

The scientists' report, published in the journal Science, describes how they used the X-ray technology, developed for use by doctors, to look inside a grapefruit-sized, reddish brown clump in the dinosaur's partially exposed chest.

The clump's size, position and features mean it can only be a heart, the researchers believe.

High metabolic rate

"Not only does this specimen have a heart, but computer-enhanced images of its chest strongly suggest it is a four-chambered, double-pump heart with a single systemic aorta, more like the heart of a mammal or bird than a reptile," said Dr Dale Russell, a palaeontologist at North Carolina State University who helped co-ordinate the study.

Willo was a plant eating dinosaur

Dr Michael Stoskopf is an expert on the comparative anatomy of mammals, reptiles and birds, and helped to produce the 3-D composite images of Willo's chest cavity.

"Willo's ventricles and aorta indicate it had completely separate pulmonary and body circulation systems, which suggests it had a metabolic rate higher than we generally see in living reptiles," he said.

"This means that dinosaurs, certainly the later ones, were probably warm blooded and engaged in active behaviour," Dr Russell told the BBC. "They weren't sluggish animals. They were like the animals that we know - birds and mammals today."

More organs

Shadows and shapes revealed by the 3-D images suggest Willo may contain other fossilised organs as well.

Dr Dale Russell: This is a first

The specimen itself is a member of the Thescelosaurus genus, and is probably a member of the T. neglectus species. Thescelosaurus means marvellous and neglectus means neglected.

"Marvellous? Yes. But I don't think this one is going to be neglected any more," Dr Russell said.

Because of the dinosaur's scientific importance and fragile condition, the North Carolina Museum of Natural Sciences is displaying the remains in their original posture, still embedded in the sandstone.

The right side of its skull, spinal column, ribs and sections of the tail are partially exposed. The left side and extremities were lost to erosion.