Ever since a new paper by Kaye et al. came out this week in PLoS One, the Paleo list servers and Blog's have been buzzing. Brain from Laelaps sums the papers results up best here by stating: "...Sampling a variety of genera from Hell Creek and elsewhere, researchers hypothesize that the structures that look like blood vessels and cells from the famous Tyrannosaurus femur are really just biofilm, slimy accumulations of bacteria that oozed into the bone and took the shape of the structures. What's more, the published data from the Tyrannosaurus protein studies showed the presence of at least some bacterial contamination, and the authors of the PLoS paper suggest that the bacteria might have contained collagen-like proteins and therefore made the findings of the earlier studies ambiguous...."
Carl Zimmer gets the perspective of Mary Schweitzer, whose original studies sparked this retest of methods: "There really isn’t a lot new here, although I really welcome that SOMEone is attempting to look at and repeat the studies we conducted. There are really several errors in wording (and spelling and grammar) in the paper by Kaye et al. that seem to underlie a fundamental misunderstanding of our work, our data and our interpretations...." Read her entire statement here (about halfway down the page, although the entire article is worth reading).