MAX IV’s Anders Engdahl was part of a team that published a landmark study about biological tissue found in a Jurassic fossil. The work published this week in Nature is one of the most comprehensive studies of its kind and sheds new light on the life of a prehistoric sea creature.
Ichthyosaurs were reptiles that roamed the Jurassic oceans 180 million years ago. They are extremely well studied and the form will probably be instantly recognisable from museums and textbooks. They resemble modern toothed whales such as dolphins and this similarity led researchers to hypothesise that the two creatures had similar strategies for survival in the marine environment. However, until now, there was little evidence to support this hypothesis. The research team led by Lund researcher Johan Lindgren went on the search for biological material within fossils to help solve this puzzle. After a lot of preparation in the lab and traveling around the world to perform experiments, they discovered that the fossil contained remnants of smooth skin and subcutaneous blubber. This is compelling evidence that the Ichthyosaurs were indeed warm-blooded and confirms the previous hypothesis. Lindgren showed visible delight when he described how you could see that the 180-million-year-old blubber was indeed visibly flexible after treatment in his laboratory.
Not only did the team discover skin and blubber, they also found the outlines of prehistoric organs. Lindgren carefully pointed out what looked like a stain on the rock, but as he outlined the shape with his finger in the air just above the fossil, it began to look a lot like a liver. Their analysis confirmed that it was indeed a liver and that biological material had survived in the rock all this time.
Not being content, the research team set out to solve another puzzle that had plagued paleontologists since they first started working on Ichthyosaur fossils. Ever since the very first specimens were excavated, people noticed a dark halo around the fossils. It almost became a characteristic of the Ichthyosaur and yet, there was no explanation. People speculated that it was a chemical reaction in the rock or the remnants of prehistoric bacteria that feasted upon the remains of the Ichthyosaur before they themselves perished. Lindgren and his team applied their battery of methods to the darkened rock and discovered that it was a skin pigment. Their finding revealed that these aquatic reptiles had darker pigment on top and lighter pigment underneath, much like modern dolphins and whales. This pigmentation type is known as countershading and is a camouflage strategy in the ocean where it is difficult to see dark objects from above and light objects from below.
Here is Johan Lindgren, explaining the study in his lab sitting next to the 180-million-year-old Ichthyosaur.
In the interview, Johan explained how this was the most comprehensive study of this type ever performed which was also confirmed by Anders Engdahl from MAX IV. Many studies of fossils focus on one key method or technique but here, the research team used a whole host of different method to study the same thing. Engdahl explained that this helps give a lot of confidence in the results. If you get the same answer from many different methods, you can be more certain of the outcome. Three of the methods that the team used in the study can be performed at synchrotrons. The first is Infrared microspectroscopy which is a specialty of Anders Engdahl. This method is not currently available at MAX IV but some of the measurements for the study were performed on the old beamline from MAX-lab which has been relocated to the Department of Biology at Lund University. The second method used was X-ray tomography which was conducted at PSI. Tomography is an imaging method used to generate 3D reconstructions. In the case of the fossil this is incredibly useful because components of the fossil can be separated digitally after the tomography image has been reconstructed. This technique will be present at MAX IV soon at the NanoMAX beamline and the DanMAX beamline. The third synchrotron-based method used was X-ray fluorescence microscopy which was done at Stanford. Now, this is use at the NanoMAX beamline and will also be a feature of SoftiMAX. Engdahl explained that STXM (Scanning transmission X-ray microscopy) which will also be carried out at SoftiMAX when it is completed would also be a good technique to use in studies of this type in the future.
Here is Anders Engdahl explaining the study and the opportunities for MAX IV in the future.
For more information about Ichthyosaurs, here is a short National Geographic film explaining their evolution, what they looked like and where they lived.