Using a technique called Resonance Raman spectroscopy, paleontologists have detected hemoglobin remnants in bone extracts from two dinosaur species, Brachylophosaurus canadensis and Tyrannosaurus rex, and confirmed that the molecule is original to these dinosaurs.
Bright field images are shown for vessels harvested as described in methods from (a) ostrich vessels soaked in hemoglobin solution under deoxygenating conditions, (b) ostrich vessels soaked in hemoglobin under oxygenated conditions, (c) vessels recovered from demineralized Brachylophosaurus canadensis and (d) Tyrannosaurus rex bone. Scale bars – 0.5 mm in (a-c) and 0.2 mm in (d). Image credit: Long et al., doi: 10.1098/rspa.2025.0175.
Still soft tissues retaining some of their original characteristics have been recovered from numerous Mesozoic vertebrate remains.
The chemical make-up of the soft tissues from two species of non-avian dinosaurs, in particular, Brachylophosaurus canadensis and Tyrannosaurus rex, has been characterized in multiple studies over the course of the last two decades.
All data support the hypothesis that these tissues are endogenous to the once-living dinosaurs.
In a new study, North Carolina State University’s Professor Hans Hallen and colleagues used Resonance Raman (RR) imaging of the tissues to confirm the presence of both heme bound to globin proteins and heme bound to goethite, a mineral associated with iron oxidization.
“Raman spectroscopy essentially uses light waves to identify a molecule’s energetic ‘fingerprint’,” Professor Hallen said.
“Resonance Raman, which we use here, takes that process one step further by using light that is already tuned to the molecule of interest — so only that type of molecule will resonate.”
“Additionally, that molecule type resonates to give a higher signal level so that its signal ‘overwhelms’ the signals from other types of molecules.”
“This strong signal allows us to find the needle (hemoglobin remnants) in the haystack (messy fossil) to see how this molecule has changed from the functional living state, revealing the chemical changes molecules undergo in deep time.”
The researchers used RR imaging to target molecules with a heme-globin bond.
They looked at samples from Brachylophosaurus canadensis, Tyrannosaurus rex, demineralized bone of the ostrich (Struthio camelus), and human blood.
“The signal increase shows that hemoglobin is present, but changes in the signal also allow us to see that as the hemoglobin degrades, goethite may form on the iron within hemoglobin,” Professor Hallen said.
“We can also pinpoint where the ring-like structure of heme is being damaged.”
“And we saw this process in both modern and ancient samples.”
The results also rule out the possibility of sample contamination.
“Raman spectroscopy will tell you what molecular bonds are present, but molecular bonds aren’t exclusive, so those bonds could come from anywhere,” said North Carolina State University’s Professor Mary Schweitzer.
“RR identifies both bonds and structure. So we know that heme is there, and that it is still bound to hemoglobin protein — contaminants like bacteria don’t have those specific bonds, so we can say that the molecules are from the animal, or in this case, the dinosaur.”
The scientists also point out that understanding how heme degrades and changes over time could help explain how fossilization occurs and why molecules can persist through millions of years.
“While the biggest finding is that we can use RR to show that pieces of hemoglobin can persist for tens of millions of years, we’ve also gotten some incredible insight into how the molecule has changed,” Professor Hallen said.
“Goethite is a mineral crystal that is known to be bio-related; that is, it forms from biological action.”
“But we didn’t know that it could bind to and stabilize protein fragments.”
“Heme has been identified in sediments that are much, much older than dinosaurs, so we know that it persists,” Professor Schweitzer said.
“Understanding why hemoglobin preserves, and the role that heme plays in the process, is really important if we want to know how these ancient molecules survive through time.”
The study appears in the Proceedings of the Royal Society A.
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B.J.N. Long et al. 2025. Resonance Raman confirms partial haemoglobin preservation in dinosaur remains. Proc. R. Soc. A 481 (2321): 20250175; doi: 10.1098/rspa.2025.0175