Scientists Find Oldest Amber Arthropods on Record
Typical amber droplets. Researchers screened 70,000 drops, resulting in the three arthropod inclusions. Scale bar: 1 mm. (University of Padova/S. Castelli)
Preserved for 230 million years in droplets of amber just millimeters long, two newly named species of mites and a fly have set a record.
They are the oldest arthropods – invertebrate animals that include insects, arachnids, and crustaceans – ever found in amber, the name typically given to globules of fossilized resin. The results, published by an international team of researchers in theProceedings of the National Academy of Sciencestoday, pave the way for a better evolutionary understanding of the most diverse group of organisms in the world.
“Amber is an extremely valuable tool for paleontologists because it preserves specimens with microscopic fidelity, allowing uniquely accurate estimates of the amount of evolutionary change over millions of years,” said corresponding author David Grimaldi, a curator in the Museum’s Division of Invertebrate Zoology and a world authority on amber and fossil arthropods.
Even though arthropods are more than 400 million years old, until now, the oldest record of the animals in amber only dates to about 130 million years. The newly discovered specimens are about 100 million years older, the first amber arthropods ever found from the Triassic Period.
The amber was buried in outcrops high in the Dolomite Alps of northeastern Italy. About 70,000 of the miniscule droplets were screened for inclusions—encased animal and plant material—resulting in the discovery of the three arthropods that were brought to the Museum’s Fossil Insect Laboratory for further study.
Two of the specimens are new species of mites, named Triasacarus fedeleiand Ampezzoa triassica. They are the oldest fossils in an extremely specialized group called Eriophyoidea that has about 3,500 living species. These ancient gall mites are surprisingly similar to ones seen today, all of which feed on plants and sometimes form abnormal growth called “galls.”
The ancient mites likely fed on the leaves of the tree that ultimately preserved them, a conifer in the extinct family Cheirolepidiaceae. Although about 97 percent of today’s gall mites feed on flowering plants,Triasacarus fedeleiand Ampezzoa triassicaexisted prior to the appearance and rapid radiation of flowering plants. This finding suggests that gall mites evolved with their hosts over time.
The third amber specimen, a fly, was not well preserved and cannot be identified. But now that the researchers have shown that amber preserved Triassic arthropods, they are eager to find more specimens.
“There was a huge change in the flora and fauna in the Triassic because it was right after one of the most profound mass extinctions in history, at the end of the Permian,” Grimaldi said. “It’s an important time to study if you want to know how life evolved.”