Rare fossils of a carnivorous plant have been found preserved in a piece of Baltic amber.
The find has shed light on the origins of a plant that traps its food using leaves that act like fly paper.
The rare fossils, described in this week's Proceedings of the National Academy of Sciences, date back to between 35 and 47 million years ago, during the Eocene.
"This is the first discovery of a carnivorous plant fossil of this type," says one of the study's authors, Professor Alexander Schmidt, of the University of Gottingen in Germany.
The researchers suggest the fossil may be an early member of the Roridulacea family of carnivorous plants, which includes Roridula.
They found the fossil leaves are strewn with multicellular stalked glands or tentacles and unicellular hairs closely resembling those found on the leaves of Roridula, which is endemic to the Cape flora of South Africa.
Roridula traps insects on sticky leaves that act like fly paper and relies on resident symbiotic insects to digest its hapless prey.
"Carnivorous plants are found in many modern plant families, each with their own way of catching prey," says Schmidt.
"This specific trap is unique to the plant in South Africa."
Widespread distribution Schmidt says the leaves were well preserved and very distinct from other flowering plant leaves, and were able to be compared with modern plant families still around today.
The researchers say the discovery shows the distribution of the Roridulacea family of carnivorous plants was far more wide spread during the Eocene than previously thought, challenging earlier notions about a Gondwanan origin of this family.
"We didn't expect to find these leaves in the European fossil record, because Roridula is restricted to South Africa," says Schmidt.
"However the amber insect fossil record does include many examples of Eocene insects that are today only found in areas like South Africa and Australia."
This means that while Europe wasn't geographically very far from its current location during the Eocene, Schmidt believes the climate of the day must have been slightly warmer.
Schmidt says most carnivorous plants on Earth today have no fossil record, the exception being seeds from the sundew Aldrovanda.
"Because they're not large, or made of wood, and because they decay quickly, carnivorous plants don't survive easily in the rock record, and so amber provides a chance to preserve something that is so rare," he says.
Schmidt and colleagues discovered two tiny leaves from the ancient carnivorous plant encased in Baltic amber which had been collected by a Hamburg couple who regularly collect and trade in amber.
"Baltic amber is the world's largest amber deposit, containing many fossils of insects and other arthropods, as well as some plant fossils," says Schmidt.
The amber was originally extracted from a mine near Kaliningrad in Russia.
While the tiny fossilised leaves were each only five millimetres long, Schmidt believes the original plant would have had much larger leaves as well.
"We have a problem with the preservation of organisms in amber, because resin flows from trees are usually too small to trap larger animals or larger fragments of plants, it's hard to enclose something the size of a maple leaf in a resin flow," says Schmidt.
"This discovery adds to a larger project trying to reconstruct the habitat of the Baltic amber forests," he adds.
"We want to find out if it was a dense dark forest, or if it was more a landscape of meadows intermixed with open woodland."