Soft Tissue from Dinosaurs Found: Intact Cells and Blood Vessels 03/24/2005
The news media are abuzz with exciting reports about the discovery of soft tissues recovered from a Tyrannosaurus rex bone;
http://www.cnn.com/2005/TECH/science/03/24/rex.tissue.ap/index.html
http://news.nationalgeographic.com/news/2005/03/0324_050324_trexsofttissue.html
http://news.bbc.co.uk/1/hi/sci/tech/4379577.stm
http://www.msnbc.msn.com/id/7285683/
http://www.nature.com/news/2005/050321/full/050321-13.html
The soft tissue, analyzed from a thighbone unearthed in Montana, was reported by a North Carolina team led by Mary Higby Schweizer and was announced in this week's issue of Science.1
The bone contained remnants blood vessels that were still soft and flexible when separated from the matrix, and even individual cells: "osteocytes with internal cellular contents and intact, supple filipodia that float freely in solution," the authors say. Leading dinosaur paleontologist Jack Horner described the bone as "a fantastic specimen." The discoverers also found soft tissues in two other tyrannosaurs and one hadrosaur from Hell Creek, Montana site. No one seems to be questioning the assumed age of the specimens being 70 million years old, even though the "geochemical and environmental factors" that could have preserved the tissues are "as yet undetermined," and extend to the molecular level:
Quote:
Whether preservation is strictly morphological and the result of some kind of unknown geochemical replacement process or whether it extends to the subcellular and molecular levels is uncertain. However, we have identified protein fragments in extracted bone samples, some of which retain slight antigenicity. These data indicate that exceptional morphological preservation in some dinosaurian specimens may extend to the cellular level or beyond.
Erik Stokstad in the same issue of Science2 says that the vessels, still flexible and elastic, are not fossilized. The announcement of intact cells is leading some scientists to think they may be able to extract DNA (although recreating Jurassic Park is out of the question). Principal investigator Schweitzer said she was shocked at the find. She didn't believe it till they repeated the extraction process 17 times. As a control, they repeated the same process on extant ostrich bones and recovered soft tissues that were "virtually indistinguishable" from those of the dinosaur.
It is not yet clear whether the original molecules in the tissues and cells were preserved or were replaced by other compounds. Earlier claims of original tissue in other kinds of multi-million-year fossilized organisms turned out to show replacement. Schweitzer told the BBC, however, that "It still has places where there are no secondary minerals, and it's not any more dense than modern bone; it's bone more than anything." As to DNA, Stokstad quotes one expert who said, "the likelihood is probably next to none" that intact DNA could have survived for 68 million years, even if the bone was protected in stable, dry, subzero conditions all that time. The BBC reporter agrees that "the ?'life molecule' degrades rapidly over thousand-year timescales, and the chances of a sample surviving from the Cretaceous are not considered seriously." Schweizer is seeking funds to do mass spectrometry on the tissues and find out.
1Schweitzer et al., "Soft-Tissue Vessels and Cellular Preservation in Tyrannosaurus rex," Science, Science, Vol 307, Issue 5717, 1952-1955, 25 March 2005, [DOI: 10.1126/science.1108397].
2Erik Stokstad, "Tyrannosaurus rex Soft Tissue Raises Tantalizing Prospects," Science Vol 307, Issue 5717, 1852, 25 March 2005, [DOI: 10.1126/science.307.5717.1852b].