Soft Tissues From T. Rex Fossil

A recently discovered Tyrannosaurus rex fossil appears to contain elastic soft tissues, blood vessels and cells, researchers report in the 25 March 2005 issue of the journal Science.

Tissues other than bone can be preserved in the fossil record, but it's usually difficult to determine their original form and composition in fossils more than a few million years old. These findings show that soft tissues can be clearly preserved for much longer, since this T. rex specimen, known as MOR 1125, is roughly 70 million years old.

Mary Higby Schweitzer and colleagues noticed unusual tissue fragments lining the marrow cavity of the MOR 1125 femur. When they dissolved the mineral deposits in the tissues, the authors were left with a flexible, stretchy material threaded with what looked like blood vessels. The treatment also released some thin, transparent soft tissue vessels that floated freely in the solution. These vessels resemble vessels from modern-day ostrich bone, the authors report.

Both the dinosaur and ostrich vessels also contained small, reddish brown dots that might be nuclei of the "endothelial" cells that line blood vessels. Certain portions of the T. rex bone also contained fibril-like structures that looked virtually identical to bone cells called "osteocytes" seen among collagen fibers in the ostrich bone.

The exquisite preservation of this tissue, which does not challenge the timing of dinosaur evolution, may open up avenues for studying dinosaur physiology and perhaps some aspects of their biochemistry, especially if researchers can identify soft tissues in other fossils as well.

— Kathy Wren

25 March 2005