The fossil is from the famous Messel locality in Germany, well known to preserve birds, mammals, fish, reptiles, insects and leaves with exceptional details.
The locality is famous for its preservation of melanin in most of the animals found here and even the structural iridescence of beetle and moth fossils. Finding the intact preening glands and the wax molecules within them is a new milestone in understanding fossil preservation.
Birds use their preening gland in maintaining their feathers. By secreting an oily substance onto their bill they can preen their feathers, which can water proof their feathers, maintain the health and durability of the feather and even protect it from microbial degradation.
Dr Jakob Vinther, a palaeobiologist at the University of Bristol’s School of Earth Sciences, has been working for a long time with researchers at the Senckenberg Natural History museum on the preservation of melanin in birds and mammals from the Messel locality.
The institution’s ornithologist Gerald Mayr had noted the preservation of the preening glands in some birds from Messel.
Dr Vinther and Gerald Mayr realised that a study of the preening glands would be extremely interesting to understand how these glands preserve, which seemed like they were composed of wax—the main constituent of the preening gland. However, the previously collected fossils have all been transferred to a plate of resin and covered in varnish, which would complicate any analysis of the fossil preening glands.
Dr Vinther said: “Usually, only melanin is preserved in these sorts of fossils; all the keratin and other proteins are lost.
“We know that some fats, or lipids, may preserve as we know these from extracts of sediments and fossil plants. We could therefore expect to find that the waxy material could be extremely well preserved and give us new insights into what may also preserve in vertebrate fossils.”
After a couple of years, the field crew from Senckenberg that excavate in Messel had discovered a new bird preserving the wax gland.
Dr Vinther contacted his colleague at the Massachusetts Institute of Technology (MIT), Roger Summons, an expert on the analysis of fossil organic molecules and his post-doctoral student, Shane O’Reilly, who were equally excited to undertake the study of the fossil bird wax.
The Senckenberg preparator, Michael Ackermann, carefully scraped out the fossilised wax, which could be scooped out of the fossil like cold butter and carefully wrapped it in sterile aluminium foil.
When the material was analysed at MIT alongside control samples from the sediment and the preserved feathers associated with the bird fossil, a clear pattern emerged: the preening gland preserved the waxy molecules produced by the bird in beautiful detail.
The sediment that hosts the fossil is a so-called oil shale, which is full of various lipid molecules produced by decaying plant and algal matter. Shane O’Reilly could clearly see a difference between the lipid molecules in the sediment and the lipids from the preening gland, as those were much longer and more complex molecules than the ones in the sediment.
The next step will be to look for fossil preening glands in dinosaurs. Dr Vinther added: “The research is a milestone for palaeontologists.
“We have discovered preserved wax material in a bird and it is likely that we can look for the origin of this important gland and see if dinosaurs also used oil glands to preen their feathers.”