Soft tissues and lipids found in a fossil bird from 48 million years ago

Fossil bird from the Messel Pit. Markings show the uropygial gland (Photo courtesy Sven Traenkner/ Senckenberg)
Fossil bird from the Messel Pit. Markings show the uropygial gland (Photo courtesy Sven Traenkner/ Senckenberg)

An article published in the journal “Proceedings of the Royal Society B: Biological Sciences” describes the discovery of a fossil bird from 48 million years ago in which the uropygial gland was preserved, a gland that secretes an oil birds use to preen their plumage. The examination showed that it still contained lipids, the oldest ever found in the remains of a vertebrate.

The bird fossil examined was discovered in the so-called Messel Pit, a UNESCO World Heritage Site “Messel Pit” near Darmstadt in Germany. It’s an important site thanks to the vast amount and variety of fossils discovered in that area. A team of researchers led by Dr. Gerald Mayr, head of the Ornithology Section at the Senckenberg Research Institute, studied this bird fossil from 48 million years ago discovering a level of conservation that surprised the researchers.

Most vertebrate fossils are just bones because soft tissues tend to decompose long before they can fossilize. However, there are environmental conditions in which soft tissues get at least partially preserved for a time long enough to get fossilized. The consequence is that we have few bird fossils that include feathers and soft tissue but the Messel Pit is one of the places where conditions allowed the fossilization of part of them.

In the specific case, an uropygial gland was preserved and researchers were able to analyze it to try to get more information on those ancient birds. Lipids are particularly stable compounds and the detailed chemical analysis carried out by the researchers shows that in this case they retained their chemical composition at least partially over 48 million years. The lipids contained in a fossil uropygial gland can be clearly distinguished from the compounds present in the rock around the fossil.

The study of this fossil is particularly interesting for this discovery and the researchers wondered if there was a connection between the antibacterial component of the preen oil produced by the uropygial gland and its conservation. Bacteria are crucial in tissue decomposition so the presence of an antibacterial agent can increase the chances of fossilization.

Dr. Gerald Mayr stated that it would be interesting to find out if feathered dinosaurs had already a uropygial gland and if they used its oil preen their plumage as their bird “cousins” do. As often happens in paleontology, the lucky discovery of a fossil and its examination with modern technologies can reveal really important information.

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