Fossil discovery reveals new species in 16-million-year-old amber

TORONTO —
U.S. scientists say they have discovered a new species of microscopic animals suspended in a piece of 16-million-year-old amber.

While these tiny creatures, known as tardigrades, have thrived on Earth for more than 500 million years, experts say the microscopic animals have almost no fossil record despite their “ubiquitous ancient lineage” and ability to survive extreme conditions, including space.

Researchers at the New Jersey Institute of Technology and Harvard University have uncovered the third clear tardigrade fossil ever found, noting that it is the “best-imaged” one to date.

“The discovery of a fossil tardigrade is truly a once-in-a-generation event,” Phil Barden, senior author of the study and assistant professor at New Jersey Institute of Technology, said in a press release. “Finding any tardigrade fossil remains is an exciting moment where we can empirically see their progression through Earth history.”

It is the first of tardigrade fossils found from the Cenozoic era, the Earth’s current geological era beginning 66 million years ago, according to researchers.

The findings were published Tuesday in biological research journal Proceedings of the Royal Society B.

Measured at just over half a millimetre, the specimen has been identified as a relative of the modern living tardigrade superfamily, Isohypsibioidea.

Scientists have named this never-before-seen species of tardigrade Paradoryphoribius chronocaribbeus. The name incorporates the Greek word for time, “chrono,” and “caribbeus,” referring to the Dominican region of La Cumbre where it was found, according to the study.

Marc Mapalo, lead author of the study and Harvard University graduate student, said in the release that the fossil appears similar to modern tardigrades at first glance given its “relatively simple external morphology.”

“However, for the first time, we’ve visualized the internal anatomy of the foregut in a tardigrade fossil and found combinations of characters in this specimen that we don’t see in living organisms now,” Mapalo said. “Not only does this allow us to place this tardigrade in a new genus, but we can now explore evolutionary changes this group of organisms experienced over millions of years.”

Tardigrades, or water bears, are known for their unusual appearance and self-preservation abilities. Researchers say the new fossil has captured “micron-level details” of the eight-legged invertebrate’s mouthparts and needle-like claws that are about 20 to 30 times finer than a human hair.

Researchers say the greatest challenge in unearthing tardigrade fossils is their size.

Barden noted that the new species is only a “faint speck in amber.” The amber also trapped a flower and other insects, including three ants, according to the study.

“In fact, Pdo. chronocaribbeus was originally an inclusion hidden in the corner of an amber piece with three different ant species that our lab had been studying, and it wasn’t spotted for months,” Barden said in the release.

Barden said tardigrades’ microscopic, non-biomineralized bodies are “uniquely suited” to be preserved in amber, which is capable of safely enveloping organisms as small as individual bacterium.

“This particular mode of fossilization helps explain the patchy fossil record,” he explained. “Fossil amber with arthropods trapped inside is only known from 230 million years ago to the present — that’s less than half of the history of tardigrades.”

While the new fossil is a major find, Barden says the research team is “just scratching the surface” of understanding living tardigrade communities.

Researchers suggests the rare fossil could provide new molecular estimates that offer insight into major evolutionary events that have shaped the more than 1,300 species found across the planet today.

“This study provides a reminder that, for as little as we may have in the way of tardigrade fossils, we also know very little about the living species on our planet today,” Barden said.