Twenty years ago, American paleontologist Mary Schweitzer made an amazing discovery. Examining a piece of dinosaur bone through a microscope, she noticed red blood cells.
It seemed completely impossible: organic remains could not survive in the fossilization process. But test after test suggested that the spherical formations were indeed the red blood cells of a Tyrannosaurus rex that died 67 million years ago.
In the years that followed, Ms Schweitzer and her colleagues found other evidence of soft tissue, including something like blood vessels and feather fibers. But skeptics argue that these are not organic tissues, but biofilms formed by microorganisms invading the fossilized bones.
Despite everything, Ms Schweitzer and her colleagues continue to build up the evidence base. This time presents the results of a molecular analysis of what is interpreted as osteocytes in the remains of T. rex and Brachylophosaurus canadensis. In one test, putative cells were exposed to antibodies targeting the PHEX protein. The latter is present in many taxa, but binds to antibodies differently in different organisms. In this case, the putative cell formations reacted in the way you'd expect from avian osteocytes (birds evolved from dinosaurs). In other experiments, antibodies targeting DNA have bound to some material in small, isolated areas within what may be a cell membrane.
In addition, using mass spectrometry, scientists have found amino acid sequences of proteins in extracts from dinosaur bones that correspond to the sequences of actin, tubulin and histone proteins present in the cells of all animals. Although some microorganisms have proteins similar to actin and tubulin, the researchers note that E. coli isolated from the soil, as well as the sediment containing the remains, did not bind to the actin and tubulin antibodies that reacted with the extract, possibly containing osteocytes.
No data was found to support the biofilm hypothesis.