One of the fossilized feathers of an ancient vulture. These feathers were preserved thanks to zeolite minerals. (Photo credit: Edoardo Terranova)
Scientists have finally solved the mystery of how the fossilised feathers of a 30,000-year-old vulture were preserved in such exceptional detail.
The Griffon Vulture (Gyps fulvus), first discovered in the Colli Albani volcanic complex southeast of Rome, Italy, in 1889, was found in remarkable condition, even retaining traces of its delicate wing and eyelid feathers.
Since its discovery, researchers have long speculated about how the bird was so well preserved. Now, in a new study published Tuesday (March 18) in the journal Geology, scientists suggest that the rare preservation of intricate detail may be due to tiny silica crystals known as zeolites, which formed when the bird's remains were buried in volcanic ash.
Experts say this is the first time that fossilised soft tissues such as feathers have been found preserved in volcanic ash.
“Fossil feathers are usually found in ancient mud layers that formed in lakes or lagoons. The vulture fossil was preserved in ash deposits, which is highly unusual,” said lead author Valentina Rossi, a paleobiologist at University College Cork in Ireland.
“We were in uncharted territory when we analyzed the plumage of the fossil vulture. These feathers are completely different from what we usually see in other fossils,” she added.
Rare preservation
The fossil was first discovered in the foothills of Italy's Mount Tuscolo in 1889 by a local landowner. Paleontologists at the time noted the unusual preservation of the feathers in the volcanic rock. However, over time, much of the fossil was lost, with only the feathers of one wing and the bird's head and neck remaining. In recent years, scientists have reanalyzed the fossil, revealing intricate details of the vulture's eyelids and skin.
In the new study, the researchers used electron microscopes and chemical tests to examine the fossilized feathers, which showed that the fossils were preserved in three dimensions. This is highly unusual for feathers, which usually leave only two-dimensional carbon imprints in rocks. Three-dimensional feathers have previously only been found in amber.
Scientists were able to see details of the feather structure down to one micron (0.001 millimetre) in size and found that the feather fossils were made of zeolite, a mineral often associated with volcanic environments.
“Zeolites are silica- and aluminum-rich minerals that are common in volcanic and hydrothermal geological settings,” Rossi explained. “Zeolites can form as primary minerals (with beautiful crystals) or can occur secondarily, through the natural alteration of volcanic glass and ash.”
This discovery marks the first time feathers have been found preserved in this way and with such a high level of detail. Additionally, no other fossils preserved in zeolite have ever been found.
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