A dinosaur bone may have preserved a trace of its blood for 115 million years.
The discovery concerns Aratasaurus museunacionali, a carnivorous dinosaur that lived in what is now Brazil. About 3 meters long, it walked on two legs. Researchers examined bones from its limbs, found in the northeast of the country. Inside, they spotted tiny shapes where small blood vessels once passed.
Artistic reconstruction of Aratasaurus museunacionali, a carnivorous dinosaur from the Cretaceous period discovered in Brazil.
Illustration: Maurilio Oliveira — CC BY 4.0, via Wikimedia Commons.
These oval shapes resemble red blood cells, the cells that carry oxygen in the blood. But their appearance alone is not enough to establish their origin. Over millions of years, minerals can replace tissues and produce misleading structures. The team therefore looked for chemical clues in the same location.
The analyses revealed traces of heme. This iron-containing substance is part of hemoglobin, which enables blood to transport oxygen. The researchers detected these traces inside the small structures observed in the bone. This association between shape and composition strengthens the hypothesis that they are ancient red blood cells.
To check that these substances did not simply come from the soil, the scientists also analyzed the rocks surrounding the fossil. They found different chemical signatures there. Several observation methods were also used to examine the shapes and the elements present. These results make contamination less likely, without ruling it out completely.
How could such traces have survived for so long? After the animal died, deposits rich in microbes may have covered its remains. Minerals may then have replaced parts of the cells while preserving their shape. The molecules associated with blood may also have survived.
Yet not all specialists are convinced. Paleontologist Mary Schweitzer points out that the observed shapes lack some features expected in the red blood cells of reptiles and birds. In these animals, these cells have a nucleus, which is absent from human red blood cells. The presence of chemical traces remains interesting, but their association with genuine cells requires confirmation.
An experiment is already underway in Australia to test this possibility. Researchers are studying whether microbial mats, similar to those found in some coastal environments, can promote the fossilization of blood. The result could help clarify the conditions that allowed these ancient traces to be preserved.