David Adam, science correspondent
Friday March 25, 2005
Scientists have raised the spectre of a "Jurassic Park" resurrection of dinosaurs after extracting what looks like blood vessels and intact cells from a Tyrannosaurus rex.
Tests on the 70m-year-old samples continue, but the US scientists have not ruled out the possibility of extracting DNA - the starting point for the cloning of dinosaurs in Michael Crichton's bestseller, which was the basis for Steven Spielberg's hit film.
The well-preserved fossil skeleton of the T-rex was unearthed in 2003 from Hell Creek, Montana, in the US. When the researchers analysed one of its thigh bones, broken during its recovery, they found a flexible, stretchy material threaded with what appeared to be transparent and hollow blood vessels. The vessels branched like real blood vessels, and some held cell-like structures.
Mary Schweitzer, from North Carolina State University, in Raleigh, who led the team, told the journal Science: "It was totally shocking. I didn't believe it until we'd done it 17 times."
The vessels closely resembled those from the bones of present-day ostriches, the scientists said. Many contained red and brown structures that looked like cells. Within those, the team discovered smaller objects similar in size to the nuclei of blood cells in modern birds.
"The vessels and contents are similar in all respects to blood vessels recovered from extant ostrich bone," the researchers report in Science.
Their next step is to determine the soft tissue found inside the bone; it might be original T-rex material. However, it could be that the proteins have been replaced by other chemicals over the centuries.
Scientists have previously recovered intact cells trapped in 225m-year-old amber, only to find the nuclei had been replaced with resin compounds.
Dr Schweitzer's group said they had identified some protein fragments that still responded to tests.
Other experts were hopeful. In the UK, David Martill, a biochemist at the University of Portsmouth, said: "There's a reasonable chance that there may be intact proteins." He speculated that it might even be possible to extract DNA.
Lawrence Witmer, a palaeontologist at Ohio University's college of osteopathic medicine, agreed: "If we have tissues that are not fossilised, then we can potentially extract DNA. It's very exciting."
If the cells do contain original biological material, the scientists would be able to investigate everything from dinosaur physiology to how the creatures evolved into birds.
Cloning a T-rex would be far more difficult. Current techniques need hundreds of nuclei from living cells, said Duane Kraemer, a cloning expert at Texas A&M University, who leads a project called Noah's Ark, which stores tissue samples from animals facing extinction. Any dinosaur DNA remaining in the cells would probably be damaged or degraded, making it impossible to use for cloning .
In the fictional Jurassic Park, scientists repaired damage using amphibian DNA. In reality, they would need to know the complete dinosaur genome. "To determine what has been damaged you need to know what the original DNA sequence was," said Dr Kraemer.
Alex Greenwood, a molecular biologist at the American Museum of Natural History, in New York, has compared trying to clone an extinct animal from damaged DNA to throwing all the parts needed to make a car down the stairs of a building in the hope that a Porsche 911 will emerge.
This has not stopped people trying, and several groups have made unsuccessful attempts to resurrect the woolly mammoth using genetic material recovered from a preserved carcass.