The secrets of amber fossils preserved in time

Frankfurt / DPA

With the help of a CT scan, Monica Solorzano Kraemer has discovered an ancient fly encased in a piece of amber from France. “Some ambers are too cloudy for a microscope,” says the scientist from Germany’s Senckenberg Society for Natural History. “With a CT scan I can look right through the stone.”
A 3D computer programme has made it possible to see every detail of the fossil, the completely preserved remains of a fly belonging to the phoridae family, a hump-backed species. And a 3D printer can produce a plastic copy that allows scientists to examine every aspect of the insect, which has been dead for millions of years.
Scientists believe that the oldest ambers are around 320 million years old. However, research into amber is one of the newest research areas at the Frankfurt-based Senckenberg society. Mexican-born Solorzano Kraemer is working together with colleagues in other countries to discover the secrets of fossils trapped in amber and copal, or tree resin, from all over the world.
The youngest ambers are 13 million years old and come from Peru. Copal is younger and a primary stage of amber. The researchers want to use the fossils to determine what the animals’ natural habitat was like back then. What did the forests look like?
They’re also comparing the fossils with today’s insects, to see the variation in species from the past and examine how changes in the environment have affected the development of the insects. They collect today’s insects with the help of sticky yellow strips.
They’ve presented their work, for example from a trip to Madagascar, in a comic, translated into four languages and aimed at children and adults alike. Their next expedition will take the scientists to New Caledonia, a group of islands off the north-east Australian coast, at the end of November.
Up to 300 insects can be encased in a piece of amber or copal just three or four centimetres in diameter. “Usually it’s only between one and 10 though,” says Solorzano Kraemer. It depends on where the amber originates.
Spiders, feathers and hair of small mammals are also sometimes found; pond skaters and flies are common, and butterflies are rare. Senckenberg has more than 13,000 pieces of amber and copal in its collection, including 300 holotypes, a single specimen upon which the identification of a new species is based.
Many of the pieces still need to be classified, says Solorzano Kraemer, who has been researching amber fossils for 14 years and has discovered 30 new species. “Amber oxidizes with time,” she says. “It gets darker until you can’t see anything.”
Storage conditions are therefore important, with 20 degrees Celsius and 40 per cent humidity considered ideal. As amber also reacts with carbon dioxide, the samples are also protected by coating them with a layer of synthetic resin.