A fossil skeleton of Hypacrosaurus, on display at the Royal Tyrrell Museum in Alberta, Canada.
Palaeontologists have announced the discovery of organic material in 75-million year old dinosaur fossils. The team claims to have found evidence of cartilage cells, proteins, chromosomes and even DNA preserved inside the fossils, suggesting these can survive for far longer than we thought.
The researchers, from the Chinese Academy of Sciences and North Carolina State University, made the discovery in skull fragments of Hypacrosaurus, a duck-billed herbivore from the Cretaceous period. These particular specimens were “nestlings”, meaning that at time of death they weren’t yet old enough to leave the nest.
Inside the skull fragments, the team spotted evidence of extremely well-preserved cartilage cells. Two of them were still linked in a way that resembles the final stages of cell division, while another contained structures that look like chromosomes.
The next step was to check whether any original molecules or proteins could still be preserved, and to do so the team conducted two detailed analyses on other skulls from the same nesting ground, and compared the results to samples from young emu skulls that are (obviously) much more recent.
The first was an immunological test, which involves applying a substance that will react if it detects antibodies from a particular cell type. In this case, the test reacted to antibodies of Collagen II, a protein commonly found in the cartilage of animals. This, the team says, suggests that remnants of the original proteins are still present.
Left: Two cartilage cells shown still connected in a way that resembles the final stages of cell division. Center: A cell containing structures that resemble chromosomes. Right: An isolated dinosaur cartilage cell with red staining that indicates the presence of DNA
Science China Press
Understandably, the reaction was far fainter for the dinosaur samples than the emus. The dinosaurs’ staining was also localized in one spot, where as in the emu it was spread across the whole sample.
In the second test, the team hunted for dinosaur DNA. They isolated individual cartilage cells from the Hypacrosaurus, and applied two different staining substances that bind to DNA fragments. And sure enough, the staining occurred in the same pattern expected for modern cells.
The implications of potentially finding DNA in these samples are huge. Current thinking says that DNA can only persist for about a million years maximum – but these fossils are 75 million years old.
“These new exciting results add to growing evidence that cells and some of their biomolecules can persist in deep-time,” says Alida Bailleul, co-lead author of the study. “They suggest DNA can preserve for tens of millions of years, and we hope that this study will encourage scientists working on ancient DNA to push current limits and to use new methodology in order to reveal all the unknown molecular secrets that ancient tissues have.”
An artist’s reconstruction of a dead Hypacrosaurus nestling (center), along with living siblings and an adult
Undoubtedly, groundbreaking discoveries that challenge our understanding of biology must be approached with caution. In the past, similar findings have faced scrutiny and generated controversy. Dr. Mary Schweitzer, a co-lead author of the recent study, captured attention in 2007 when she uncovered preserved proteins and soft tissues in a Tyrannosaurus rex femur.
However, skeptics emerged, questioning the validity of the bold assertion. Some argued that the data had been misinterpreted, while others proposed that bacterial biofilms, formed during the fossils’ time underground, may have presented a misleading appearance under microscopic examination. Another study even suggested that the dinosaur samples had potentially been contaminated with ostrich DNA in the laboratory where they were analyzed.
That said, the researchers on the new study seem to have pre-empted some of these arguments. They point out that Collagen II isn’t produced by microbes, so bacterial biofilms wouldn’t cause the tests to come back positive. Biofilms would also create very different patterns in the DNA staining tests than what was seen here. And finally, the team says that the comparisons to emu samples were conducted in completely different labs, so there was no chance of cross-contamination.
While Jurassic Park remains firmly in the realm of fiction, the possibility that dinosaur DNA and organic molecules could persist for tens of millions of years is still fascinating, and it could teach us far more about these captivating, ancient creatures.