A study claims to have found preserved cells, proteins and even DNA in the 75-million-year-old fossils of a baby duck-billed dinosaur.
An international team of researchers from China, Canada and the United States conducted microscopic analyses of skull fragments from a clutch of eggs, embryos, hatchlings and nestlings belonging to Hypacrosaurus, a type of duck-billed dinosaur that lived in what is now the Two Medicine Formation in Montana, US, during the late Cretaceous period.
In a sensational paper published in National Science Review, the authors found exquisitely preserved cells within calcified cartilage tissues. Two of the cartilage cells were still linked by an intercellular bridge — just as would be seen near the end of cell division — while elsewhere dark material reminiscent of cell nuclei could be observed in the specimens. One even held tangled coils that resembled chromosomes.
“I couldn’t believe it, my heart almost stopped beating,” recalled Dr Bailleul, lead author and palaeontologist from the Chinese Academy of Sciences.
The team next found that the organic matrix surrounding the cells reacted with antibodies to collagen II, but the surrounding bone did not. This is significant because collagen II is found only in cartilage, while collagen I dominates in bone.
“This immunological test supports the presence of remnants of original cartilaginous proteins in this dinosaur,” said author Mary Schweitzer, professor of biology at North Carolina State University. “Additionally, bacteria cannot produce collagen, which rules out contamination as the source of the molecules.”
The researchers also applied two DNA stains, DAPI (4,6-diamidino-2-phenylindole) and PI (propidium iodide), which bind specifically to DNA fragments in cells. Some of the cells showed internal positive binding in the same pattern as seen in modern cells, suggesting some original dinosaur DNA is preserved.
“We used two different kinds of intercalating stains, one of which will only attach to DNA fragments in dead cells, and the other which binds to any DNA,” Schweitzer explained. “The stains show point reactivity, meaning they are binding to specific molecules within the microstructure and not smeared across the entire ‘cell’ as would be expected if they arose from bacterial contamination.”
These findings fly against conventional scientific understanding, which maintains — based on modelling and experimentation — that DNA is expected to only last under 1 million years.
“Although bone cells have previously been isolated from dinosaur bone, this is the first time that cartilage-producing cells have been isolated from a fossil,” said Bailleul. “It’s an exciting find that adds to the growing body of evidence that these tissues, cells and nuclear material can persist for millions – even tens of millions – of years.”
Schweitzer was more circumspect. “I’m not even willing to call it DNA because I’m cautious, and I don’t want to overstate the results,” said Schweitzer. “There is something in these cells that is chemically consistent with and responds like DNA.”
But even if these 75-million-year-old cartilage cells do hold remnants of intact dinosaur DNA, don’t expect Jurassic Park to really come to life. In all likelihood, the information these cells contain would be too limited to sequence a whole genome. But even a small dose of knowledge could tell us more than we ever knew about this cute-looking herbivorous dinosaur. [APBN]