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75 million-year-old blood cells found in dino bones

Scientists have identified structures that appear to be red blood cells and collagen-like fibres in dinosaur bones dating back to the Cretaceous.

T. rex skeleton on display at the Smithsonian Museum. US Department of Agriculture

Hold on to your butts: Scientists have found some dinosaur cellular material, and it looks like it might be red blood cells.

Eight 75 million-year-old bones dating back to the Cretaceous in poor condition have been found to contain what looks to be soft tissue remnants, says a new paper published today in the journal Nature Communications.

Remnants of soft tissue have been found in fossils in the past, but only those that had been very well preserved, and only very rarely. A team of researchers from Imperial College London who studied the fossils said the result indicates that surviving prehistoric soft tissue might be much more common than previously supposed.

It also indicates that soft tissue samples might be able to survive for far longer than previously supposed. Although exceptionally well-preserved samples contain soft tissue dating back tens of millions of years, their identification has been controversial. Previously, many scientists had thought protein molecules decay much more quickly, surviving no longer than 4 million years.

"What is particularly exciting about our study is that we have discovered structures reminiscent of blood cells and collagen fibres in scrappy, poorly preserved fossils. This suggests that this sort of soft tissue preservation might be widespread in fossils," explained study co-author Dr Susannah Maidment, a junior research fellow Department of Earth Science and Engineering.

Claw fossil within which red blood cell-like structures were found. Laurent Mekul

"Early indications suggest that these poorly preserved fossils may be useful pieces in the dinosaur jigsaw puzzle to help us to understand in more detail how dinosaurs evolved into being warm blooded creatures, and how different dinosaur species were related."

The eight samples studied by the team were loaned by the Natural History Museum's Sternberg and Cutler collections, which have housed the fossil fragments for more than a century. First, they used scanning electron microscopy, which uses a beam of electrons to examine the structure, location and composition of the soft tissue within the fragments.

Next, they used a focused ion beam -- which works similarly to scanning electron microscopy, but with beams of ions that at higher currents can be used for etching and milling -- to slice into the samples and observe their internal structure. A transmission electron microscope was also used to detect the fibrous structures.

In one part of a fossilised claw, the team identified microscopic ovoid structures with a denser core -- these could be red blood cells. In another fragment, the team found fibrous structures with banding similar to modern-day collagen fibres.

Top: Carbon-rich material and structures found within the fossils; Bottom: Modern emu samples for comparison. Bertazzo et al., Nature Communications

The team compared the blood cell structures with a blood sample taken from an emu, since birds are distantly related to dinosaurs. The fossil structures had some similarities with the emu sample, particularly in the organic signatures. The team hopes that the find could help determine when and how dinosaurs evolved a warm-blooded, avian metabolism.

The collagen-like structures -- if indeed they do prove to be collagen -- could also be used to determine dinosaur group relationships, since collagen structures vary between animal groups. Collagen could be used to link related dinosaur groups.

The next step is to examine a wider range of fossils to see exactly how far back soft tissue has been preserved, how widespread it is and why it may have occurred.

"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."

Just so long as they don't try sequencing and splicing any DNA they might find...