Fossilized cartilage reveals dinosaur cells in incredible detail
Paleontologists have isolated cartilage cells from an exceptionally well-preserved dinosaur fossil in China. The cells' nuclei still contain traces of biomolecules and other organic structures, and the scientists are even able to tell which stage of the natural cycle specific cells were in at time of death.
Bones are usually all we have left to work with when reconstructing dinosaurs, but occasionally scientists get lucky and find more. Feathers, skin, eggs, and even brains have been discovered, revealing new insights into these amazing animals.
Some of the best-preserved specimens come from the Jehol Biota, an ecosystem from the early Cretaceous period in northeastern China. The landscape was dominated by wetlands and shallow lakes, and, most importantly, frequent volcanic eruptions that were key to slowing down decomposition of remains.
"Geological data has accumulated over the years and shown that fossil preservation in the Jehol Biota was exceptional due to fine volcanic ashes that entombed the carcasses and preserved them down to the cellular level," says Li Zhiheng, co-author of the study.
It is from this deposit that researchers from the Chinese Academy of Sciences and Shandong Tianyu Museum of Nature have plucked the latest stunning specimen, dated to about 125 million years ago. The creature in question is called Caudipteryx, a bird-like dinosaur that stood about knee-high and sported long tail feathers.
The team extracted a section of cartilage from its right femur, and found that it had undergone a type of fossilization known as silicification. The original organic tissue was replaced with silica, which helps to preserve the cells.
In fact, the preservation was so complete that the researchers were able to differentiate between cells that had been healthy at the time of death and those that were already dying, due to the natural cell cycle.
After the researchers demineralized some of the sample, they stained it with a chemical called hematoxylin, which binds to the nucleus of a cell and shows up purple. And sure enough, one of the dinosaur cartilage cells reacted in the exact same way as a cartilage cell from a chicken: it turned purple, highlighting the nucleus and threads of chromatin, structures that make up chromosomes.
Intriguingly, the nucleus and chromatin are where DNA molecules are found inside cells. That suggests that some remnants of dinosaur DNA could potentially be preserved inside, but that’s a long shot that will require far more work to verify. After all, DNA isn’t thought to survive much longer than a million years, let alone 125 million.
"Let's be honest, we are obviously interested in fossilized cell nuclei because this is where most of the DNA should be if DNA was preserved," says Alida Bailleul, co-author of the study.” So, we have good preliminary data, very exciting data, but we are just starting to understand cellular biochemistry in very old fossils. At this point, we need to work more.”
This isn’t the first study to find evidence of cell nuclei and potential DNA in dinosaur fossils. Last year, a team, including some of the scientists from the new study, uncovered signs of nuclei, proteins and chromosomes in cells from a large herbivore called Hypacrosaurus, found in Canada. However, the Caudipteryx specimen is about 50 million years older.
The research was published in the journal Communications Biology.
Source: Chinese Academy of Sciences