WASHINGTON - A unique 46-million-year-old mosquito fossil with a belly full of dried blood has been found in a Montana riverbed, US researchers said Monday.
"It is an extremely rare fossil, the only one of its kind in the world," said Dale Greenwalt, lead author of the study in the Proceedings of the National Academy of Sciences.
Cutting-edge instruments detected the unmistakable traces of iron in her engorged abdomen, but just what creature that blood came from is a mystery since DNA cannot be extracted from a fossil that old.
Greenwalt said it might have been blood from a bird, since the ancient mosquito resembles a modern one from the genus Culicidae, which likes to feed on our feathered friends.
"But that would be pure speculation," said Greenwalt, a retired biochemist who volunteers at the Smithsonian Museum of Natural History in Washington.
While far from the oldest known mosquito fossil - that honour goes to a 95-million-year-old mosquito in amber in Myanmar - entomologist Lynn Kimsey of the University of California said it was "a very exciting find."
"Having an actual blood-engorged female mosquito associated with males in the same fossil formation is hugely unlikely," said Kimsey, who was not involved in the research.
"Here, the authors have been able to use mass spectrometry to elucidate the abdominal contents and thus blood-feeding in a fossil some 40 million years old," she added, describing the research as "impressive."
Greenwalt said he became fascinated with fossilized insects several years ago.