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Almost all known have been in the Northern Hemisphere, and it’s long been “an enigma” that scientists have found few in southern regions that once comprised the supercontinent Gondwana, said David Grimaldi, an entomologist at the American Museum of Natural History who was not involved in the discovery.

This marks the first time researchers have identified ancient beetles, flies, ants and wasps in fossilized tree resin in South America, said Ricardo Pérez-de la Fuente, a paleoentomologist at the Oxford University Museum of Natural History, who also was not involved in the new study.

“Amber pieces are little windows into the past,” Pérez-de la Fuente said, adding that the discovery will help researchers understand the evolving interactions between flowering plants and insects that lived during the era of the dinosaurs.

The researchers uncovered hundreds of fragments of amber, some containing ancient insects, pollen and tree leaves, at a sandstone quarry that’s on the edge of what is today the Amazon basin.

But today’s rainforest is much different from what dinosaurs roamed through, Herrera said. Based on an analysis of fossils in the amber, the ancient rainforest contained species of ferns and conifers, including the unusual Monkey Puzzle Tree, that no longer grow in Amazonia.

“It was a different kind of forest,” said Herrera.

The amber deposits were previously known to geologists and miners who worked at the Genoveva quarry. Study co-author Carlos Jaramillo at the Smithsonian Tropical Research Institute first heard of them about a decade ago and set out to find the exact location, aided by geology field notes.

“I went there and realized this place is amazing,” Jaramillo said. “There’s so much amber in the mines,” and it’s more visible in the open quarry than it would be if hidden under dense layers of vegetation.

Researchers will continue to analyze the amber trove to learn more about Cretaceous-era biodiversity -- including the insects that contributed to evolution by feeding on flowering plants. “Amber tends to preserve things that are tiny,” said Grimaldi.

“It’s the time when the relationship between flowering plants and insects got started,” said Pérez-de la Fuente. “And that turned out to be one of the most successful partnerships in nature.”

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