Blood vessels recovered from T. rex bone

• 19:00 24 March 2005
• NewScientist.com news service
• Jeff Hecht

Palaeontologists have extracted soft, flexible structures that appear to be blood vessels from the bone of a Tyrannosaurus rex that died 68 million years ago. They also have found small red microstructures that resemble red blood cells.

The discovery suggests biological information can be recovered from a wider range of fossil material than realised, which would greatly help the tracing of evolutionary relationships.

The preservation found by the researchers is extraordinary - far better than traditionally expected in dinosaur bone. But that may be because researchers have not been looking hard enough at their finds. Mary Schweitzer at North Carolina State University, US, has also extracted similar soft structures from a few other dinosaur bones.

The leg bone came from a skeleton called B-rex found in a remote canyon in South Dakota, in 2000 by a member of Jack Horner's research team at the Museum of the Rockies in Montana. The 107-centimetre-long femur - small for a T. rex - was intact when found, and its hollow interior had not been filled with minerals. That is unusual for a long-buried bone.

However, with a protective plaster jacket built around it, the bone was too heavy for a helicopter to retrieve it from the remote site and it had to be broken in half. When Horner's group split the bone, they carefully took samples for Schweitzer, then working at the Museum of the Rockies.

"Elasticity and resilience"

Bones are built by cells called osteocytes which are nourished by a rich fabric of blood vessels. The osteocytes secrete proteins which collect the calcium compounds that give bones their strength.

To see what remained of this internal structure, Schweitzer soaked samples of the core of the bone in a solution that dissolved the calcium compounds. This left what she describes as "a flexible vascular tissue that demonstrates great elasticity and resilience".

For comparison, she then examined ostrich bones, as these birds are the largest and closest living relatives of T. rex. She found similar structures when she removed the calcium from the ostrich bones and treated the mixture with enzymes to break down collagen fibre in the bony matrix.

Protein sequencing

Other researchers have previously recovered traces of protein from dinosaur bones, and indeed just two weeks ago Schweitzer reported traces of protein in 70 million year old dinosaur eggs.

"[The T. rex paper] suggests that biological and biochemical information might be recoverable from a wide range of fossil material," says Angela Milner of the Natural History Museum, in London, UK, who has detected proteins in Iguanadon bone. "There certainly seem to be blood vessels," she told New Scientist.

The next step will be to isolate proteins and try to sequence them. Comparing protein sequences could help trace relationships with other prehistoric beasts and with animals alive today. Schweitzer decline to discuss DNA because she does not work with it, but DNA is far less stable than proteins so is usually broken into fragments, even in tissue that has been frozen since the ice age.

Journal reference: Science (vol 307, p 1952)