DNA is the nucleic acid that contains most of the genetic information of animals. However, this biomolecule degrades rapidly in nature, and the oldest DNAs in fossils date back just over a million years. Nevertheless, researchers have just discovered highly conserved dinosaur cells that may even contain DNA.

The team of researchers, from the Chinese Academy of Sciences, managed to isolate and color cells from a fossil at least 125 million years old. The animal was a small peacock-like dinosaur, called Caudipteryx It turned out that the dinosaur's cells were exceptionally well preserved compared to other fossils.

These cells, in turn, were part of the cartilaginous tissue attached to the femur of the animal. This type of tissue, it is worth noting, has cells that are quite close together and compact, with little extracellular fluid.

However, given the conservation of cartilage, the researchers decided to try staining the dinosaur cells - in several different ways - and observing them under a microscope.

The striking result is that one of the dyes, hematoxylin-eosin, stained the dinosaur's cells the same way that those of most animals end up stained. Hematoxylin, for example, binds to DNA and colors the nucleus purple, while eosin makes the cytoplasm pink.

According to the researchers, it is still impossible to be sure about the composition of the nucleus of the cells in this fossil. Still, there is a possibility that some of the chromatin was preserved there.

"Let's be honest, we're obviously interested in the fossilized nucleus of the cell because that's where most of the DNA should be if the DNA were preserved," co-author Alida Bailleul says in a statement.

Cell of Caudipteryx stained with hematoxylin. Image: Alida Bailleul et al. / Communications Biology 2021

What preserved the dinosaur cells for so long?

According to the research, very specific conditions allowed the cartilage cells of this dinosaur to be preserved for so long and with such detail. It turns out that the fossil ended up impregnated with silica and aluminum compounds soon after the animal's death.

In other words, most of the organic matter in the cytoplasm of the cells was replaced by silica. This may have also preserved the chromatin structures (DNA condensed in the nucleus) and perhaps even the genetic information.

Also according to the research, chromatin may have been replaced by similar compounds, which would also cause the hematoxylin staining. However, this is not very likely, since the chicken cells stained nearly identically in the research.

A second fossil, found earlier in Canada, therefore had similar signs of cellular conservation. However, the specimen from Hypacrosaurus was at least 50 million years younger than the new Caudipteryx .

In addition, dinosaur cells are rarely preserved in any form. Soft tissues end up degraded more quickly by organisms. no Caudipteryx However, it is even possible to see differences in certain cells.

Some of them, thus, were relatively healthy, while others were already degrading even before the animal died. This, it should be noted, is a natural process and, again, rarely preserved in fossils.

The research is available in the journal Communications Biology.