In their study, recently published in the Journal of Anatomy, the scientists conclude on the basis of micro-computed tomography analyses that the tubercles may have served as part of an internal "armor" to protect against deadly neck bites from mammalian predators.

Over the course of evolution, many animal species have developed different strategies to defend themselves against predators—from sophisticated camouflage and venom to protective armor. A research team led by ornithologist Dr. Gerald Mayr from the Senckenberg Research Institute and Natural History Museum Frankfurt has now identified an unusual variant in a group of Eocene birds.

"We have examined a number of fossil avian cervical vertebrae, all of which exhibit a pronounced tubercular surface structure—a striking feature that is unknown in modern birds. We hypothesize that these tubercles are part of a protective 'reinforcement' of the cervical spine," explains Mayr.

Such cervical vertebrae covered by conspicuous tubercles were first observed in roughly 48 million-years-old fossils of various bird species from the Messel Pit in Hesse, and they were subsequently also identified in similar finds from the London Clay Formation with an age of up to 53 million years.