Heme signatures in mineralized red blood cells within vascular canals of a 115-million-year-old dinosaur bone.

Heme-derived tetrapyrroles and red-blood-cell–like ellipsoidal microstructures are preserved in limb bone of Aratasaurus museunacionali (115-million-year-old theropod), with heme B as the principal signal.

• Why it matters: Endogenous biomolecules in vertebrate fossils are hard to verify because labile compounds degrade and are easily contaminated.
• What they did: Bone extracts were analyzed by high-performance liquid chromatography–mass spectrometry for heme B and other tetrapyrroles, then localized using Raman spectroscopy and transmission electron microscopy for heme-related porphyrin and heme elements plus hausmannite (Mn3O4).
• The result: The heme B–linked signatures and spatial co-localization with mineral-stabilizing elements support an endogenous blood origin and enable molecular confirmation of mineralized red blood cells in dinosaur bone.

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