Three tiny creatures from the Triassic period are the oldest ever to be discovered preserved in amber - about 100 million years older than any other amber arthropod ever collected.
The specimens, one fly and two mites, were found in droplets of amber from northeastern Italy just a few millimeters across. They could help scientists understand the evolution of arthropods - the most diverse group of organisms in the world, including insects, arachnids, and crustaceans.
"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," says David Grimaldi of the American Museum of Natural History.
Amber, or fossilized resin, ranges in age from the Carboniferous (about 340 million years ago) to about 40,000 years ago. It's been produced by many plants, from tree ferns to flowering trees, but predominantly by conifers.
But even though arthropods are more than 400 million years old, until now the oldest record of the animals in amber dates to about 130 million years. The newly-discovered arthropods take that date back to 230 million years.
About 70,000 of the amber droplets, most between two and six millimeters long, were screened for inclusions.
Two of the specimens are new species of mites, named Triasacarus fedelei and Ampezzoa triassica. They are the oldest fossils in an extremely specialized group called Eriophyoidea that has about 3,500 living species, all of which feed on plants and sometimes form abnormal growth called galls. The ancient gall mites are surprisingly similar to ones seen today.
"You would think that by going back to the Triassic you’d find a transitional form of gall mite, but no," says Grimaldi.
"Even 230 million years ago, all of the distinguishing features of this family were there — a long, segmented body; only two pairs of legs instead of the usual four found in mites; unique feather claws, and mouthparts."
The mites likely fed on the leaves of the tree whose resinpreserved them, a conifer in the extinct family Cheirolepidiaceae.
The third amber specimen, a fly, can't be identified as there's not much left of it apart from the antennae.
Now that the researchers have shown that Triassic arthropods can be found preserved in amber, they plan to look for more.
"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," says Grimaldi. "It’s an important time to study if you want to know how life evolved."