12 publishers · first seen Mon, 02 Nov 2026 19:00 UTC · updated Thu, 05 Nov 2026 17:04 UTC
Scientists have discovered what they believe to be fossilized red blood cells in a 115-million-year-old dinosaur fossil from Brazil. The discovery, published in the Proceedings of the National Academy of Sciences, is based on the detection of heme, an iron-rich molecule in hemoglobin, which is the protein in red blood cells that carries oxygen. The fossil, of a small, meat-eating dinosaur called Aratasaurus museunacionali, was discovered in a mine in northeastern Brazil in 2008 and sent to researchers in 2024 for analysis. The researchers found numerous structures resembling red blood cells inside the dinosaur's hind leg bone, which they believe to be the oldest red blood cells ever found in a dinosaur fossil. However, some experts remain skeptical, noting that soft tissues like blood generally break down quickly after death and that environmental factors can produce red blood cell look-alikes.
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