Researchers have found what appears to be red blood cells and connective tissue, discovered in 75 million-year-old dinosaur fossils.

Researchers studying a fossilized dinosaur claw at the Imperial College in London have discovered microscopic ovoid structures in it that appear to be red blood cells. Another fossil fragment held fibrous features that resemble collagen, that makes up tendons and ligaments. These tissues are not fossilized, but are rather remnants of soft tissue.

Chemical analysis of the blood cells shows a composition similar to that of a modern-day emu. The size of the cells can also provide a clue as to whether or not dinosaurs were warm-blooded or not. "There’s an extremely well-known relationship within individual vertebrate groups that the smaller the red blood cell, the faster the metabolic rate," explains Dr. Susannah Maidment, co-author of the findings. "Animals with fast metabolic rates will tend to be warm blooded, while animals with slower metabolic rates are going to be more cold blooded."

Typically, tissue remnants like this are found only under certain circumstances, where the specimen was found in an "exceptionally preserved" state, but these findings were found in fossils that have been sitting in a museum for more than a century. According to Dr. Maidment, "If you’re finding soft tissues in these kinds of fossils, maybe this kind of preservation might be more common than we realized, and might even be the norm."

But does it mean that something like Jurassic Park could ever become a reality? Given present knowledge and technical skills, it’s impossible, but who knows what the future may bring.