48-million-year-old preen oil lipids discovered in a bird fossil
A fossil preen gland in a 48-million-year-old bird, showing the fossil gland in detail as it was found before sampling and after preparation. The creamy white material is fossilised preen gland oil/wax. Right hand side: Modern bird with the preen gland prepared out from a modern Sickle-Billed Vanga (artificially coloured to highlight the preen gland)
Researchers have shown that a well-preserved preen gland in a 48-million-year-old bird fossil contains its original fat molecules.
The fossil is from the famous Messel locality in Germany, well known to preserve birds, mammals, fish, reptiles, insects and leaves with exceptional details, including stomach contents and original colour.
“Animal soft tissue fossils are rare discoveries but, when found, provide exquisite insight into past biological diversity and fossil formation – that is why Messel is so special” said Dr. Shane O’Reilly, UCD geochemist and lead author on the study.
The study came about after co-author Gerald Mayr – an ornithologist from the Senckenberg Natural History Museum who has studied birdfossils from Messel for over two decades – and the Messel field crew unearthed a bird fossil that appeared to contain intact preen glands.
The preen gland, also called the uropygial gland, is an important gland in modern birds that produces a waxy oil birds use for waterproofing and maintaining the health of their feathers.
Dr. Mayr and his colleague, Dr. Jakob Vinther – a palaeobiologist from the University of Bristol and also co-author on the study – had been waiting for such a find for a number of years.
“Usually, only melanin is preserved in these sorts of fossils; all the keratin and other proteins are lost” said Dr. Vinther.
“Previously collected fossils have all been transferred to a plate of resin and covered in varnish, which would complicate any analysis of the organic composition of the glands” he added.
Jakob and Gerald quickly contacted Professor Roger Summons, a geochemist in MIT and global expert in studying molecular fossils in petroleum and sedimentary rocks, to look at chemical composition of the wax material.
“I was a postdoctoral researcher working with Roger and jumped at the opportunity to get involved” said Dr. O’Reilly.
“For decades, organic geochemists have been studying molecular fossils in petroleum and sedimentary rocks and making important discoveries about the history of life on Earth. Surprisingly, we have paid relatively little attention to preservation of organic molecules in vertebrate bone fossils and soft tissues fossil” said Dr. O’Reilly.
Using a technique called mass spectrometry to look at the chemical composition of a tiny amount of the fossil wax, the geochemist found distinct fat, or lipid, molecules preserved within the gland that were very different to the surround sediment and other parts of the fossil.
“By studying the fossils within the fossil, and picking out the molecules coming from the algae and plants that made up the sediment, we could clearly see that a portion of the original waxy molecules that make up preen oil were preserved in the fossil gland” said Dr. O’Reilly.
“Finding the intact preen glands and the fat molecules within them is a milestone in our understanding of fossil formation as it shows that fat molecules can preserve well and are important for preservation of certain animal soft tissues” he added.
When asked about what next, Dr. O’Reilly said: “This research raises exciting new questions and research directions. How far back in time can we find fossil preen glands? What other fat-rich animal tissues are preserved at the molecular level? Did feathered dinosaurs also engage in preening?”
‘Preservation of uropygial gland lipids in a 48-million-year-old bird’ by S. O’Reilly, R. Summons, G. Mayr and J. Vinther in Proceedings of the Royal Society B
Sven Tränkner, Gerald Mayr, Sonja Wedmann, Michael Ackermann
Shane O’Reilly, firstname.lastname@example.org
Additional media coverage of this research:
Nature Research Highlights https://www.nature.com/articles/d41586-017-04696-4