Frozen in time 112 million years ago, an entire ecosystem preserved in amber has been unearthed from a quarry in Ecuador. The scene contains bugs, pollen, and even strands of spider web.
This is the first large discovery of insect-laden amber in South America, providing an unprecedented view of Cretaceous life in the Southern Hemisphere.
The amber, found at Genoveva quarry in Ecuador, has preserved at least five orders of insects, including a variety of flies, a fungus beetle, wasps, and a caddisfly.
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It also caught evidence of arachnid activity, in the form of a fragment of spider web. The way the strands are oriented suggests the web may have been built in the style of modern orb-weavers, though it lacks the sticky droplets typical of these kinds of webs.
"These findings provide direct evidence of a humid, resinous forest ecosystem and its arthropod fauna in equatorial Gondwana during the Cretaceous Resinous Interval," paleobiologist Xavier Delclòs from the University of Barcelona and colleagues explain in their paper reporting the finds.
Gondwana was an enormous ancient land mass or 'supercontinent' that began to break apart during the Triassic and Jurassic, forming many of today's southern continents, including South America, Africa, Antarctica and Australia.
Amber is fairly common in the Northern Hemisphere, but has only been discovered intermittently in the southern half of the planet. During the Barremian period, around 122 million years ago, massive amounts of resin were formed by coniferous trees around the world, which reigned over all plants until about 70 million years ago.
This sticky substance – a mixture of carboxylic acids, essential oils, and hydrocarbons – helps trees to heal from damage, and defends them from those who want to eat or infect their roots and branches.
This amber was formed by araucariacean trees, which, though widespread during the Jurassic and Cretaceous, are represented by just a few Southern Hemisphere species today.
Delclòs and his team identified two different kinds of amber in the quarry: one formed from the resin seeping from a tree's roots underground; the other formed above ground, when resin came into contact with the air and trapped insects moving through the trees.
While insect amber is definitely the most famous kind, it's actually relatively rare; most known amber deposits are from root resin, which tends to contain very few samples of other life forms.
However, even below ground, Cretaceous amber specimens from the Northern Hemisphere tend to include evidence of tree resin-eating fungi. While present, these were surprisingly scarce in the Genoveva samples.
This could explain why there was so much root resin to be found at this site: perhaps, the authors suggest, the soils were so saturated with water that the fungi were suppressed.
Above ground, tree resin can act like a sticky trap, collecting impressively intact specimens of the invertebrate population for us to study millions of years later.
"This discovery, and the associated plant remains in the amber-bearing rocks, enhance our understanding of the Gondwanan arthropod fauna and flora inhabiting forests along its western margin during a time interval of major ecosystem transformation," the authors write.
Future field work, they hope, could help scientists get a better idea of the way South American flora and fauna relate to other Gondwanan regions, where amber is also present, but yet to be investigated.
This research was published in Communications Earth & Environment.