For the first time, amber with insects inside has been discovered in South America, capturing a moment from 118 million years ago when flies, beetles and other six-legged animals of Cretaceous Ecuador became trapped in the sticky resin secreted by trees.
Surely they struggled, but in vain. The insects died, but encased in this tree glue, they did not decay. The microbes that would have returned them to elemental form can’t survive without oxygen. As the resin hardened and slowly fossilized over millions of years, the insects were perfectly preserved – from the glare in their compound eyes to the little hairs on their little legs.
The amber bed was discovered during quarrying operations in the Hollín Formation of Ecuador’s Oriente Basin, according to Xavier Delclòs and colleagues, writing Thursday in Communications Earth & Environment.
Amber-encased insects and spiders are fairly common in the northern hemisphere and have even been found in the Middle East, as well as Australia, New Zealand and Antarctica. But until now, none had ever been reported from Mesozoic South America. Yet there they were, in what the researchers called a “major occurrence” of amber.
Back then, Ecuador was located near the equator and had been part of the southern supercontinent of Gondwana. The insects lived in a lovely humid, thick forest perfect for arthropod life and the animals that would eat them, though no predators have been found in the quarry – at least not yet.
The resin is believed to have been exuded by araucariacean conifers, the team deduced. The sheer volume of resin found in the Genoveva quarry suggests these resin-producing trees were dominant in this Gondwanan rainforest — a fact that had remained unclear until now.
This aligns with what we know of resin production in the Northern Hemisphere. Today, the main resin secreters – yew, pine, spruce and other conifers – can exude entire sheets of the stuff. That said, in many ancient amber deposits up north, we still don’t know which specific trees were responsible.
In this case, the researchers believe they do. It’s worth noting that ancient conifers didn’t look much like the conifers of today, but resin is resin – and apparently secretion evolved very early on, likely thanks to the resin’s protective, antibiotic properties.
When the resin drips out, it hardens within a few weeks. But the process of fossilization can take from about 2 to 10 million years, geologists estimate.
Insects apparently arose in the Devonian period, over 400 million years ago, and were fossilized in stone, but we don’t find them in resin if only because there were no trees yet. The earliest known amber was found in coal seams in Illinois and dates to about 320 million years ago. By then, resin-secreting conifers had emerged.
Such extremely early amber is rare. Paleontologists and geologists have noted a major leap in amber incidence around 120 million years ago – right in line with the age of the Ecuador deposit.
As mentioned, most amber has been found in the northern hemisphere. The amber found in the southern half of the planet includes the same suspects – chiefly bugs. But this is the first time that amberified bugs have been reported from South America – a discovery offering precious information about Gondwana’s ecosystem.
The researchers identified two different types of amber. Most formed underground around the resin-producing tree root. Some of them are bigger than footballs – though they contain no insects or plants inside. The ones that do, come from resin that dripped down tree bark and hardened in the air. These are packed with a wealth of flies, beetles, ants and wasps – even a bit of spider web (though preserved spider webs aren’t new: Amberified spider web has been found and with a spider to boot, and some with prey wrapped in primordial silk).
Both types of Ecuadorian amber are mostly translucent yellow but some are greenish or reddish, the authors say.
Sadly, so far no dinosaur tails or baby heads that could compete with the unbelievable specimens coming out of Myanmar have been found in Ecuador, but the day is young – even if it began 112 million years ago.