Researchers studying an 115-million-year-old dinosaur limb bone from Brazil report ellipsoid structures and chemical traces of heme, but some experts remain unconvinced.
Researchers studying an 115-million-year-old dinosaur limb bone report they have found tiny ellipsoid structures, about 20 micrometers in diameter, that may be fossilized red blood cells, along with preserved heme, the oxygen-carrying component of hemoglobin.
The bone belonged to Aratasaurus museunacionali, a small feathered theropod dinosaur that lived around 115 million years ago. It came from Mina Pedra Branca, a fossil-rich site in northeastern Brazil within the Romualdo Formation. Paleontologists dug up the partial hind limb in 2008.
The team prepared thin cross-sectional slices of the bone and used focused electron beams to image its internal structure. That revealed ellipse-shaped microstructures within the limb’s fossilized network of blood vessels. A chemical map showed the ellipsoids were full of iron, carbon and nitrogen, components of heme. Laser-based molecular analysis suggested the presence of porphyrins, ringlike organic compounds found in blood and precursors of heme. The researchers also separated and identified the molecular contents of a bone extract to rule out contamination from other porphyrins, such as chlorophyll.
The researchers say the mineral hausmannite, a manganese oxide found within the ellipsoid structures, may have acted as a time capsule, preserving the cellular structures and protecting molecules within, including collagen amino acids.
Mary Schweitzer, a paleontologist at North Carolina State University who was not involved in the study, said she is not convinced the team has definitively identified heme compounds. She noted that the heme biomarkers do not appear to be localized to the round structures alone, as would be expected in fossilized blood cells, but come from analysis of the entire bone. She also said the proposed red blood cells differ in size and shape compared with red blood cells from living birds and reptiles.
Schweitzer said the study’s use of multiple analytical techniques is an exciting advancement for the field and that she is hopeful some molecules from the dinosaur itself remain preserved in the bone.
Lead author Kliti Grice, organic geochemist and John Curtin Distinguished Professor at Curtin University in Perth, Australia, said the approaches could be applied to other fossils to ask how much original biological information may still be hidden within them. She said it is too early to draw conclusions about the physiology of Aratasaurus based on one specimen, and that it is unknown whether this preservation is extraordinarily rare or simply overlooked in other fossils.
Timothy Cleland, a physical scientist at the Smithsonian Institution’s Museum Conservation Institute who was not involved in the study, said finding evidence of heme does not mean DNA has survived, since heme and DNA are different molecules that would fossilize in different ways.
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This article was drafted with AI assistance and checked against the sources above. Company claims are reported as claims. Cover image is AI-generated.
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