When it comes to fossils, differentiating bone from muscle can be tricky. The task can even border on impossible if the fossil was subjected to high pressure that resulted in flattening. Faced with this difficulty, researchers from the CNRS, the French National Museum of Natural History (MNHN) and the synchrotron Soleil, have developed a new and non-destructive method. They observed that, depending on the type of fossilized tissue, the distribution of some kinds of metals, the so-called rare earth elements, varied. A useful trick, seeing as their level of concentration is measurable using fluorescence imaging. Published on 29th January in PLOS One, the study should significantly expand the field of investigation in paleontology.
Flat fossils are very common. Despite the level of pressure they have undergone, the anatomy of some of these organisms has been remarkably well preserved. Invaluable information is, thus, hidden inside, but is not always recoverable. During the process of fossilization, these organic remnants experience physicochemical transformations that render the usual imaging techniques, such as optical microscopy or tomography, ineffective.
Observing the distribution of rare earth elements turns out to be more effective. These chemical elements have the particularity of binding to certain tissues more than others. This provides a great opportunity when it comes to clearly establishing contrasts within the anatomy of a fossil without altering it. The data thus collected via imaging following Synchrotron radiation allows direct observation of the characteristics of the sample, even when hidden under a thin layer of rock.
The researchers were able to detect the presence of a skull bone
in the shape of a toothed blade in one of the fossils observed.
(CNRS/MNHN Pierre Gueriau)
Three 100-million-year-old fossils have been subjected to the method already: a shrimp and two fish. The results have revealed never-before-observed anatomical characteristics that are particularly helpful in establishing evolutionary relationships between species.
The potential perspectives of this new method are considerable for paleontology, but not only. It also represents a great opportunity for understanding the process of fossilization, thanks to the clues rare earth elements give about the environment in which the fossil was preserved.