A tiny bug trapped in amber gives clues of tectonic movements

Amber is a fossilized tree resin, but if you encountered it in nature, you might not even realize what you were looking at – because it is very different from that of jewelry. The amber jewelry is bright yellow, transparent and beautiful, while the amber "rough" looks good, rough – essentially like pebbles. Miners who find amber send it to professionals for treatment purposes or, sometimes, to researchers who are looking for inclusions or other interesting aspects. Fortunately, it was also the case of the above sample, which came from Myanmar and was sent to Shuhei Yamamoto, at Chicago's Field Museum of Natural History.

After cleaning, cutting and polishing the sample, Yamamoto noticed something very unusual: a species of beetle ever discovered, linked to modern creatures living under the bark of trees.

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"This is a very rare find," said Yamamoto, a Field Museum researcher and senior author of an article in Journal of Systematic Palaeontology describing the new species.

While the giant dinosaurs dominated the land and the sea, these small insects conquered a milder environment: the parts under the bark of decaying trees. Its long and thin antennas are a smoking gun that tells Yamamoto Propiestus lived in an environment similar to today's paddle beetles. Its long antennas are a revealing sign of its heritage and, given its habitat, it is understandable that it was trapped in amber.

"The antennas probably had an extremely sensitive sensory organ capacity," said Yamamoto. Structures resembling smaller hair, attached perpendicular to the antennas, would have increased its ability to detect the environment. "There would not have been a lot of space available in the beetle habitat, so it was important to be able to detect everything," he says.

The same sample, with a pen for reference. Image credits: Field Museum.

The small insect also offers information on something much bigger: the tectonic movement. The fossil was found in Myanmar, but its closest relatives are found in South America – which is not even close to Myanmar, located in Southeast Asia. But 100 million years ago, they were much closer, linked in a supercontinent called Gondwanaland. Gondwana has finally separated, but the moment is still uncertain – this new evidence shows that the two geographical areas were always connected (or very close).

"Like koalas and kangaroos today, some animals that we believe lived in Gondwana are only found in one part of the world. Although Propiestus went extinct a long time ago, our discovery probably shows some amazing connections between the southern hemisphere and Myanmar, "said Yamamoto. "Our conclusion is consistent with the assumption that, unlike what is happening today, Myanmar was once located in the southern hemisphere."

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