When you think of dinosaurs, perhaps the dynamic images of Jurassic Park come to mind, or maybe visits to the museum to admire dinosaur skeletons and other fossils. What you may not realize is that these skeletons are more than just rocks of fossilized bones – they can contain preserved soft tissues such as muscle fibres and cells.
A study at the Imperial College in London led by Sergio Bertazzo and Susannah Maidment has found what appears to be collagen protein fibers and red blood cells preserved in 75-million year old dinosaur specimens. The study is particularly interesting because the fossils used were poorly preserved and had no external sign that the soft tissues would be found. Harder material like bone is more easily preserved, so usually soft tissue is found in only the best-preserved samples. This could mean that soft tissue preservation is more widespread in fossils than previously believed. Bertazzo and Maidment are co-authors for a paper published June 9th in Nature Communications detailing the results of the study.
Cretaceous dinosaur bone samples from the collection of the Natural History Museum in London were examined using methods of advanced material characterization, such as secondary ion mass spectrometry. Six of the eight specimens were from the Dinosaur Park Formation, a major geological unit in Southern Alberta. The fossils included a theropod claw, chasmosaurus rib, hadrosaur toe, ankle bones and other fragments, the toe of a horned dinosaur, and a rib of an unidentified dinosaur.
Through the use of scanning and transmission electron microscopes, the researchers saw that instead of bone crystallites, there were structures consistent in appearance to collagen fiber remains and presumed red blood cell remains. The samples then underwent time-of-flight secondary ion mass spectrometry (ToF SIMS), which focuses a beam of ions onto a sample surface producing secondary ions, which are then analyzed for information about the molecules and elements present on that surface. The results revealed amino-acid fragments typical of collagen. Also, the mass spectra results for the suspected red blood cells were similar to that of emu whole blood, and birds are commonly thought to be a descendant of dinosaurs.
The examination of these soft tissues can provide clues about the relations between types of dinosaurs and their evolution, as well as additional information about their physiology and behaviour.
For individual vertebrate groups, the smaller the red blood cell, the faster the metabolic rate, meaning that animals with fast metabolic rates tend to be warm blooded, and those with slower rates tend to be cold blooded. However, it is unknown whether this relationship holds true for dinosaurs. A larger sample size of blood cells from a variety of dinosaur species could help answer this question and provide clues about the lifestyles these dinosaurs had. If they were cold-blooded they may have acted slow and reptile-like, but if they were warm-blooded, they could have been more bird-like.
Examination of the collagen protein can be done via collagen fingerprinting, which is based on the idea that its molecule structure is unique to different animals. Similarities in collagen structure could help differentiate between closely related dinosaurs and distant relatives. This would provide more information regarding dinosaur relatedness and family trees.
The research team says that further research is required to confirm what it is that they are imaging. However, the ability to find these structures in fossils that have not been exceptionally preserved could pave the way for further biochemical and cellular investigations, leading to more insight into how these creatures lived and evolved.
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