A fossilised louse that lived in the plumage of birds 44 million years ago has been found with the preserved remains of feathers in its gut.
By Paul Rincon
BBC News Online science staff
The specimen from Germany is in superb condition and may be the first example of a fossil bird louse on record.
The find confirms that lice are a very ancient group of insects and suggests birds may have inherited the parasites from early feathered dinosaurs.
Details of the discovery appear in the Royal Society journal Biology Letters.
Researchers Torsten Wappler, Vincent Smith and Robert Dalgleish found small structures in the insect's abdomen which they conclude are feather barbules - the smallest branching unit of a bird feather.
The lice eat away on bird feathers, chewing with their sharp mandibles. The barbules in the fossil look just like those that can be seen in the guts of modern avian lice when viewed under the microscope.
"It's very rare that you have evidence of the last meal of an ancient insect," co-author Dr Smith, a zoologist at the University of Glasgow, UK, told BBC News Online.
The specimen was discovered in the volcanic crater of Eckfeld maar near Manderscheid, Germany. The crater once formed a freshwater lake with an original depth of 110m.
Rapid sedimentation over 250,000 years, alkaline conditions and an absence of oxygen assisted the exceptional preservation of the fossil.
The louse, which has been assigned the name Megamenopon rasnitsyni, bears a startling resemblance to a present-day group of lice that live on aquatic birds.
"Because this specimen looks like modern lice that live on some shorebirds and ducks, we can place it in a phylogenetic context and get some idea of the host it was likely to have lived on," said Dr Smith.
Pin-like feather barbules can be seen in the louse fossil's abdomen
"What we can do is use this fossil to calibrate a molecular evolutionary tree for lice."
"If the age of lice predates that for birds, because the group as a whole are parasitic, the original host must have been a dinosaur."
It is not known what sort of birds were living at Eckfeld maar 44 million years ago, during the Eocene epoch. As a result, it is not possible to tell what species the louse might have lived on.
But the authors believe this raises the possibility that the original hosts for parasitic lice were dinosaurs and not mammals and birds as other researchers have suggested.
In 1998, researchers reported the discovery of fossil eggs, possibly mites, on a fossilised feather from Brazil dating to 120 million years ago, a time when the dinosaurs were very much in existence.