Scientists at Imperial College London have discovered what appear to be the remnants of soft tissue and red blood cells in poorly preserved dinosaur bones dating back 75 million years.
It's not a harbinger of "Jurassic Park," because no traces of DNA were found in the fossil samples. But the researchers said the discovery means paleontologists may be able to find much more biological material in dinosaur bones than previously thought.
"We still need to do more research to confirm what it is that we are imaging in these dinosaur bone fragments, but the ancient tissue structures we have analyzed have some similarities to red blood cells and collagen fibers," study author Sergio Bertazzo said in a statement. "If we can confirm that our initial observations are correct, then this could yield fresh insights into how these creatures once lived and evolved."
The team examined fragments of eight dinosaur bones from the Cretaceous period, which lasted from 145 million to 66 million years ago and ended with the extinction of the dinosaurs. The bones were dug up in Canada more than a century ago and have been housed at the Natural History Museum in London.
Using advanced electron microscopes and mass spectrometry to analyze the samples, the researchers detected what appear to be calcified collagen fibers — as well as red blood cell-like structures that were "surprisingly similar" to the blood found in the modern emu, a large flightless bird native to Australia.
It's not the first time soft tissue has been found in dinosaur fossils. In 2005, researchers reported the discovery of 68 million-year-old soft tissue preserved inside the leg of a T. rex unearthed in Montana. A similar case, involving a duckbilled dinosaur known as Brachylophosaurus, came to light in 2009.
Related: What Preserved T. Rex tissue? Mystery Explained at Last
Imperial College scientists say that, unlike those earlier cases, the dinosaur fossils they examined were poorly preserved. "Our study is helping us to see that preserved soft tissue may be more widespread in dinosaur fossils than we originally thought," said Susannah Maidment, another study author at Imperial College.
The study was published Tuesday in Nature Communications — and lit up Twitter with the hashtag #dinoblood.
Thomas Holtz Jr., a vertebrate paleontologist at the University of Maryland, said the findings appear sound. "It does seem to be the best interpretation of their observations. They used multiple microscopic and chemical analyses to test their ideas, and the structures do match the expected values for red blood cells and collagen fragments," he told NBC News by email. "This new study shows that fossil bone that is pretty crappy (in terms of the bone structure) still can provide wonderful chemical and cellular information. And it reinforces the observation that we know less about the details of decay and preservation than we thought we did."
But Peggy Ostrom, a biogeochemist at Michigan State University, said it's difficult to know for sure what the researchers found without additional tests. "I believe that these and all previous soft tissue work need to incorporate amino acid and protein-sequencing data.There are also new amino acid compound-specific approaches that would be revealing," she said in an email.