This story is in the news again, so I’ve reposted my description of the paper from 3½ years ago. This is an account of the discovery of soft organic tissue within a fossilized dinosaur bone; the thought at the time was that this could actually be preserved scraps of Tyrannosaurus flesh. There is now a good alternative explanation: this is an example of bacterial contamination producing a biofilm that has the appearance of animal connective tissue.
Read GrrlScientist’s explanation and Greg Laden’s commentary and Tara Smith’s summary of the recent PLoS paper that tests the idea that it is a biofilm.
Look! A scrap of soft tissue extracted from dinosaur bone:
It has been reported in Science this week that well-preserved soft tissues have been found deep within the bones of a T. rex, and also within some hadrosaur fossils. This is amazing stuff; fine structure has been known to be preserved to this level of detail before, but these specimens also show signs of retaining at least some of their organic composition. What the authors have done is to carefully dissolve away the mineral matrix of the bone, exposing delicate and still flexible scraps of tissue inside.
Here, for example, is a piece of endothelial tissue, or the tubelike epithelia that line blood vessels and form capillaries. It is compared to a similarly prepared piece from fresh ostrich bone; you can tell the T. rex fragment has undergone some changes, but it’s comparable in size and organization to the bird sample.
Looking more closely with a scanning electron microscope, here’s a similar piece of T. rex blood vessel that has ruptured, spilling out its contents. Maybe those cells don’t look perfectly preserved, but they’re darned close.
And lastly, here’s a closeup of the surface of that epithelia, compared with an ostrich epithelium. The cells here are very, very flat, and the nuclei are the thickest part, bulging up and giving the surface a pebbled appearance. The T. rex epithelium has a similar pebbly look, suggesting that just maybe there is even some subcellular structure preserved.
How could this be? Here’s the authors’ explanation.
…we demonstrate the retention of pliable soft-tissue blood vessels with contents that are capable of being liberated from the bone matrix, while still retaining their flexibility, resilience, original hollow nature, and three-dimensionality. Additionally, we can isolate three-dimensional osteocytes with internal cellular contents and intact, supple filipodia that float freely in solution. This T. rex also contains flexible and fibrillar bone matrices that retain elasticity. The unusual preservation of the originally organic matrix may be due in part to the dense mineralization of dinosaur bone, because a certain portion of the organic matrix within extant bone is intracrystalline and therefore extremely resistant to degradation. These factors, combined with as yet undetermined geochemical and environmental factors, presumably also contribute to the preservation of soft-tissue vessels. Because they have not been embedded or subjected to other chemical treatments, the cells and vessels are capable of being analyzed further for the persistence of molecular or other chemical information.
So, basically, these cells were entombed in a thick mineral sarcophagus, protected from bacteria and other external insults. There have to have been other factors at play—cells are full of enzymes that trigger a very thorough self-destruct sequence at death—so I’m definitely looking forward to the molecular analysis. Even if their form was preserved, I expect these cells to be denatured monomer soup on the inside.
Schweitzer MH, Wittmeyer JL, Horner JR, Toporski JK (2005) Soft-Tissue Vessels and Cellular Preservation in Tyrannosaurus rex. Science 307(5717):1952-1955.