Whitefly insect fossils have been found in Miocene-age crater lake sediments at Hindon Maar, near Dunedin, and they are so small, they can barely be seen by the human eye.
Study co-author and University of Otago geology Emeritus Prof Daphne Lee said the extremely rare fossils added to the expanding insect fauna revealed in the maar.
"These little fossils are the first of their kind to be found in New Zealand, and only the third example of such fossil puparia known globally."
She said it was difficult to see much with the naked eye, and it would have been easy to miss the fossils.
"So you see the fossilised leaf, and you look a bit closer and you see these little dots on it.
"Initially, I thought they were just little bits of dirt stuck to the fossil, and I would have just brushed them off.
"But my colleague [Dr Uwe Kaulfuss] has what I think are X-ray eyes — he can tell at a distance that there’s something really interesting there.
"He realised that there was something completely different about it."
The fossils are black with an oval-shaped body (about 1.5mm by 1.25mm in size), and have some similarities to modern-day whiteflies, such as the shape and colour.
However, they differ in that all the segments of the body are distinctly defined by deep sutures (grooves).
Co-author, University of Gottingen (Germany) researcher and former University of Otago geology postdoctoral fellow Dr Uwe Kaulfuss was most excited by the "extraordinary" way the fossils had been preserved — attached to the underside of a fossilised leaf.
"Fossils of adult whitefly insects are not uncommon, but it takes extraordinary circumstances for the puparia — the protective shell the insect emerges from — to become fossilised," he said.
"Some 15 million years ago, the leaf with the puparia must have become detached from a tree, blown into the small lake and sank to the deep lake floor to be covered by sediment and become fossilised.
"It must have happened in rapid succession as the tiny insect fossils are exquisitely preserved."
He said the new genus and species described in the study revealed for the first time that whitefly insects were an ecological component in ancient forests on the South Island.
Prof Lee said until about 20 years ago, the total number of insects in New Zealand that were older than the Ice Ages was seven.
"New discoveries such as these from fossil sites in Otago mean we’ve gone from knowing almost nothing about the role played by insects, to a new appreciation of their importance in understanding New Zealand’s past biodiversity and the history of our forest ecosystems."
She said while most people were interested in big fossils, most animals in forests are insects.
"There are 14,000 insects in New Zealand and 90% are found nowhere else in the world.
"Discovery of these minute fossils tells us this group of insects has been in Aotearoa New Zealand for at least 15 million years.
"This provides a well-dated calibration point for molecular phylogenetic studies."
Other small fossils new to science have also been found at Otago sites this year, including the first dancefly, cranefly, phantom midge and marsh beetle fossils from New Zealand.
"That’s really only the tip of the iceberg. There’s plenty more to be discovered," she said.
