I bring it up here, hoping people have more information. The articles are written for the general public and have stated "red blood cells", etc. It makes it easier to track down the associated articles by asking those that are interested, then it is to google and go through 100 articles.
Yes, other people can use google for you.
From the abstract of Schweitzer's paper:
Soft tissues are preserved within hindlimb elements of Tyrannosaurus rex (Museum of the Rockies specimen 1125). Removal of the mineral phase reveals transparent, flexible, hollow blood vessels containing small round microstructures that can be expressed from the vessels into solution. Some regions of the demineralized bone matrix are highly fibrous, and the matrix possesses elasticity and resilience.
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