Soft tissue found in TWO Triceratops
First Triceratops: In the Proceedings of the Royal Society B: Biological Sciences paper titled, Soft tissue and cellular preservation in vertebrate skeletal elements from the Cretaceous by Mary Schweitzer, Jack Horner, et al., describe the discovery within a Triceratops horridus bone of:
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"Hollow, transparent and flexible vessels [which] were slightly pigmented" and its "Osteocytes… had pigmented elongate cell bodies, some with internal contents and short, stubby filipodia."
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Of the various dinosaur soft tissue types, the paper says:
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"As arguably the most labile and easily degraded of the structures we observed, the presence of soft vessels is enigmatic. They are neither biomineralized nor have any obvious inherent characteristics that would favour preservation…"
And of bacterial contamination and biofilms, in the year before the publication of the primary opposing theory, Schweitzer, et al., wrote:
"The possibility that microbes may have invaded bone and vascular channels after death, secreting extracellular polymeric substances (EPS) that subsequently mineralized, was also considered. If deposition of mineral upon microbial biofilm allowed retention of flexibility in one case, it is feasible to propose that the same process contributed to the preservation of the original vessel walls."
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And back in 2007, the authors write that while they remain open to further pending analysis of the osteocytes, they "consider these cell-like structures to be remains of original cells."
Second Triceratops: See ScienceDirect.com for the peer-reviewed 2013 paper published in a prestigious journal presenting the most extraordinary photographs of cells, not floating in solution, but still anchored to the bone in the place where they grew when this particular dinosaur roamed the earth. See also the preliminary report about how scientists traveled to the Hell Creek Formation in Montana, excavated a Triceratops horn, and like Harvard, and dozens of other universities, broke it open and... guess what... soft tissue, which in this case was beautifully preserved in situ osteocytes!