Dinosaur Blood Discovered: 115 Million Years Old and Exceptionally Well Preserved

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At a Glance

The theropod dinosaur Aratasaurus museunacionali lived 115 million years ago in northeastern Brazil. An international team discovered small, mineralized structures resembling red blood cells in the bones of its hind limb.

The chemical evidence is decisive. Microscopic examinations alone cannot reliably distinguish such structures from mineral formations, changes during fossilization, or later microbial growth. Using spectroscopic and molecular analyses, however, the team identified hemoglobin, a component of hemoglobin, as well as amino acids associated with collagen. The study was published in Proceedings of the National Academy of Sciences.

The Discovery in Detail

The fossil was discovered in 2008 in the Brazilian state of Ceará. It is a partially preserved, articulated hind limb from a juvenile animal approximately 3.12 meters long. Aratasaurus belonged to the group of theropod dinosaurs that evolved in relation to today’s birds.

Inside the bones, the researchers discovered tiny, spherical structures in the vascular canals. Their shape and size matched descriptions of red blood cells. They then examined these structures more closely using microscopic, spectroscopic, and molecular methods.

The chemical signals detected blood molecules. They differed from the signals in the microbial layer surrounding the fossil. According to the team, this argues against external contamination and supports the conclusion that the molecules examined originated from the dinosaur bone.

El Mundo describes the study as the first to document red-blood-cell-like structures together with chemical evidence of hemoglobin in a dinosaur fossil. It also describes the discovery as the oldest evidence of dinosaur blood found to date.

Why the Chemical Analysis Was Decisive

In paleontology, a cell-like shape cannot automatically be interpreted as a cell. A similar structure could also have been produced by a mineral, by aging processes during fossilization, or by microorganisms that colonized the bone after the animal’s death.

The team therefore combined several independent lines of evidence. In addition to morphology and size, the chemical analyses support a biological origin for the structures. Amino acids associated with collagen were also identified. Collagen is a structural protein found in bones as well as other animal tissues.

As far as we know, this is the first study to document fossilized structures similar to red blood cells, accompanied by in situ chemical evidence related to hemoglobin, in a dinosaur fossil. I believe this is a historic discovery because we have managed to bring together several independent lines of evidence.

Hausmannite and a Low-Oxygen Environment

Exceptionally good preservation is not automatic with tissue as delicate as this. The researchers suspect that several conditions worked together: rapid burial, a low oxygen concentration, a microbial environment, and subsequent mineralization.

Particularly notable is hausmannite, an oxide or mineral of manganese. It was persistently associated with the spherical microstructures. According to the team, the mineral environment could have enclosed and stabilized the blood cells and their molecular components, allowing them to remain chemically detectable despite the long period of burial.

The researchers compare the process to a petrified time capsule. Rapid burial enclosed the animal, the low-oxygen environment slowed decomposition, and later mineralization stabilized the delicate remains.

What the Find Means for Paleontology

The finding expands the possibilities of molecular paleontology. If comparable structures and biomolecules are detected in additional fossils, researchers could gain new information about the physiology, metabolism, and evolution of extinct animals.

The size of red blood cells is associated with metabolic characteristics in different vertebrate groups. Such structures could therefore provide clues about oxygen requirements and activity levels. The current find does not yet allow such physiological conclusions to be drawn directly, but it opens up a new methodological path.

The discovery could also be significant for museums. According to Kliti Grice, the bone does not look unusual at first glance. Molecular information could therefore also be hidden in fossils that have not yet been examined using spectroscopic and molecular methods.

Normally, soft tissues, cells, and biomolecules degrade rapidly after death. In this case, the microbial layer, the low-oxygen conditions, and subsequent mineralization appear to have created a highly unusual preservation environment. We observed manganese mineralization, including the presence of hausmannite, associated with the structures similar to red blood cells.

Martin Van Kranendonk, Director of the School of Earth and Planetary Sciences at Curtin University, points to possible links with astrobiology. The findings could change assumptions about how delicate biological structures may be preserved under difficult conditions. This is a possible avenue of research, not evidence of blood or other signs of life on Mars.

The species name museunacionali recalls the Museo Nacional in Brazil, which was severely damaged by a fire in 2018. The dinosaur was scientifically described in 2020 on the basis of the fossil.

The finding therefore relies on the interplay of morphology and chemistry: structures resembling red blood cells, hemoglobin signals, and collagen-related amino acids were detected in a 115-million-year-old bone. The find shows that extraordinary molecular information can also be preserved in fossils that initially appear unspectacular.