For the time, soft tissue-like structures that appear to be red blood cells and collagen fibres have been found in 75-million-year-old (Cretaceous) dinosaur specimens that are not well preserved. Till date, soft tissues not older than a few million years have been found only in extremely well preserved samples.
Totally eight dinosaur fossil samples from the Natural History Museum, London were studied. The results were published two days ago in the journal Nature Communications .
“In our samples, we showed preservation occurred only in some micro regions of the fossil. We showed for the first time that you can have preservation of soft tissues in micro regions of fossils that are not well preserved,” Sergio Bertazzo the first author of the study from the Department of Materials at Imperial College London said in an email to this Correspondent.
Palaeontologists may have to rewrite the conditions needed for soft tissue preservation in old samples if further studies do confirm the presence of erythrocyte and collagen in the poorly preserved samples.
The discovery could help in better understanding of the conditions needed for soft tissue preservation and could “pave the way for biochemical and cellular investigations of the remains of extinct animals,” notes Bertazzo. In addition, the soft tissue can help palaeontologists to understand the physiology and behaviour of extinct animals.
Explaining why soft tissues were never seen in old samples that were not well preserved, Mr. Bertazzo said: “The key point is that we have applied different methods not commonly used by palaeontologists. Also, it might be the case that not many researchers ever went looking for soft tissues in fossils that are not exceptionally preserved.”
The researchers examined part of a fossilised dinosaur claw and identified tiny ovoid structures with an inner denser core. Similarly, four samples showed fibrous structure similar to calcified collagen fibres found in modern bones. Unlike mammalian red blood cells that are devoid of a nucleus, nucleus is found in red blood cells of birds and other non-mammals.
After initial analysis using a scanning electron microscope, the composition of collagen was studied using mass spectrometry. “We found peaks that are consistent with fragments of amino acids present in collagen,” the authors write. Similarly, the erythrocyte-like structures inside the dinosaur sample were found to be similar to that of whole blood of modern emu birds.
“[Finding the proteins] was a surprise to us. But ours was not the first paper showing that,” he noted. “While it is impossible to completely rule out contamination, we do not know how we could get an artefact [of a protein] with a really similar mass spectrum pattern as our control.”
Besides confirming the chemical composition, one of the samples showed a clear banding of about 67 nanometre length. This is typical of banding observed in a collagen. However, the erythrocyte-like structures are about 2 micrometres in length, much smaller than the 9-15 micrometre-long erythrocytes of birds probably due to shrinkage during fossilisation.
“We still need to do more research to confirm what it is that we are imaging in these dinosaur bone fragments, but the ancient tissue structures we have analysed have some similarities to red blood cells and collagen fibres. If we can confirm that our initial observations are correct, then this could yield fresh insights into how these creatures once lived and evolved,” Mr. Bertazzo told in a release.