New York: A new study co-led by researchers in the US and China has pushed back the first-known physical evidence of insect flower pollination to 99 million years ago - during the mid-Cretaceous period.
The revelation is based upon a tumbling flower beetle with pollen on its legs discovered preserved in amber deep inside a mine in northern Myanmar.
The fossil comes from the same amber deposit as the first ammonite discovered in amber, which was reported by the same research group earlier this year.
The fossil, which contains both the beetle and pollen grains, pushes back the earliest documented instance of insect pollination to a time when pterodactyls still roamed the skies - or about 50 million years earlier than previously thought.
"It's exceedingly rare to find a specimen where both the insect and the pollen are preserved in a single fossil," said David Dilcher, an emeritus professor in the Indian University's Bloomington College of Arts and Sciences.
Aside from the significance as earliest known direct evidence of insect pollination of flowering plants, this specimen perfectly illustrates the cooperative evolution of plants and animals during this time period, during which a true exposition of flowering plants occurred, he elaborated in a paper published in the journal of the Proceedings of the National Academy of Sciences.
The shape and structure of the pollen shows it evolved to spread through contact with insects. These features include the pollen's size, "ornamentation" and clumping ability.
The grains also likely originated from a flower species in the group eudicots, one of the most common types of flowering plant species, he said.
The insect in the amber is a newly discovered species of beetle, which the study's authors named Angimordella burmitina.
Prior to this study, the earliest physical evidence of insect pollination of flowering plants came from Middle Eocene.
The age of the new fossil was determined based upon the age of other known fossils in the same location as the fossilized beetle's discovery.
The co-lead author of the study is Bo Wang, an amber fossil expert at the Nanjing Institute of Geology and Palaeontology, where the specimen was procured and analyzed.