This artistic reconstruction shows Jehol Biota as well as the preserved specimen of Caudipteryx found there. (Image credit: ZHENG Qiuyang)
In the 125-million-year-old fossils of dinosaurs from China, DNA remnants may be found. If these microscopic structures were indeed DNA, it would be the oldest known preservation of chromosome material within a vertebrate fossil.
The DNA is contained within the chromosomes of a cell's nucleus. Researchers have found evidence of cell nucleus structures in fossils from plants and algae that date back many millions of years. Scientists even suggested that microfossils dating back to 540 million years ago may contain preserved nuclei.
These claims can be controversial because it is difficult to tell if a fossilized nucleus is actually a random blob created by the fossilization process. Researchers compared fossilized cartilage of the feathered, peacock-sized dinosaur Caudipteryx to cells from modern chickens in a new study published in Communications Biology on Sept. 24, 2014. They found structures that looked similar to chromatin or threads of protein and DNA in the fossils.
"The fact they are seeing it is really fascinating, and it suggests that we need to continue to do more research on what happens to DNA, chromosomes, and cell death," stated Emily Carlisle, a doctoral candidate who studies microscopic fossils at the University of Bristol in England, but was not part of the new research.
Dino DNA?
Answering the burning question, "No," is the answer. We are far from resurrecting dinosaurs using their fossilized DNA.
Alida Bailleul, a paleobiologist from the Chinese Academy of Sciences, who was responsible for the new research, said in an email to Live Science, "If there's any DNA or DNA-like molecules in there, it'll be as a scientific guess very chemically modified"
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Bailleul stated that if paleontologists are able to identify chromosome material from fossils, they might be able one day to decipher a portion of a genetic sequence. This could provide some insight into the physiology of dinosaurs.
Researchers must first determine if DNA exists. Most paleontologists believed that decay and rot destroyed the cells' contents before fossilization could occur. Carlisle explained to Live Science that any microscopic structure found in cells was considered to be collapsed cell contents. This includes organelles, membranes, and other structures. Recent discoveries by paleontologists of legitimate cell structures have been made in fossils. One example is the 190 million-year old fern cells, which were described in Science 2014 as a result of being buried in volcanic rock and fossilized in such a rapid manner that they were frozen during cell division. Some of these cells contain chromosomes that are clearly visible.
Bailleul and her coworkers reported in 2020 the possibility of DNA preservation in the skull of an infant Hypacrosaurus. This was a type of duck-billed dinosaur, which lived 75 million years ago. It was found in Montana. The cartilage, which is the connective tissue that forms the joints, was the place where the DNA was discovered.
Bailleul stated that cartilage was a good tissue for cell preservation and is more than bone.
Image 1 of 3. The researchers compared stained cells from the Caudipteryx cartilage specimen (called STM4-3), with cells taken from adult chicken cartilage. Some slides show cells stained with H&E while others are displayed under transmitted or polarized lights (PL). CC by 4.0 (Image credit to Zheng et al./ Communications Biology Picture 2 of 3. Here's a photo showing the Caudipteryx fossil on a full slab. A close-up of the right femur is shown (b), which shows the fascinating cells that scientists discovered. CC by 4.0). (Image credit Zheng et al./ Communications Biology image 3 of 3 Reconstructions of the Jehol Biota, and the preserved specimen of Caudipteryx. (Image credit: ZHENG Qiuyang)
Hidden in stone
The researchers used a well-preserved Caudipteryx specimen held by the Shandong Tianyu Museum of Nature, China, for their new study. The fossil was found in northeastern Liaoning. It has plenty of preserved cartilage. Researchers stained it with the same dyes that are used to image DNA in modern tissue. These dyes attach to DNA and change it to a particular color depending on which dye is used. This allows DNA to stand out from the rest of its nucleus. Bailleul and her colleagues found that cartilage cells have structures similar to nuclei, with chromatin in the interior.
Related: Photos: Fossilized dinosaur embryo discovered
Bailleul warned that the similarities between stained dinosaur nuclei and modern cells does not prove that there is DNA within them. She explained that this means that parts of original organic molecules are present, possibly some original DNA, but that we don't know for certain. We just have to figure out what these organic molecules are.
Carlisle stated that imaging clearly shows nuclei. However, it is harder to identify fossilized cells because no one knows how they degrade. It is possible that the nucleus contents could just collapse into structures that look similar to chromosomes, but they are actually just a jumbled collection of meaningless mineralized junk. However, it is possible that some of the original molecular structure may be preserved by fossilization. A 2012 study found that bone DNA will eventually be completely degraded in 7 million years. However, this timing could depend on the environment.
Carlisle stated, "It would really be interesting to do more experiments into this, looking at what occurs inside the nuclei rather than just what happens from the surface."
Bailleul hopes to collect more chemical information with her colleagues to determine the identity of these mysterious structures.
She said, "I hope we are able to reconstruct a sequence someday, someday somehow." Let's just say that I could be wrong but also could be right.
Original publication on Live Science
