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(CNN)Microscopic tardigrades have thrived on Earth for more than 500 million years, and may well outlive humans, but the tiny creatures don't leave behind many fossils.
Hiding in plain sight, the third-ever tardigrade fossil on record has been found suspended within a piece of 16-million-year-old Dominican amber.
The find includes a newly named species, Paradoryphoribius chronocaribbeus, as a relative of the modern living family of tardigrades known as Isohypsibioidea. It's the first tardigrade fossil from the Cenozoic, our current geological era that began 66 million years ago.
The study published Tuesday in the Proceedings of the Royal Society B.
Beneath a microscope, tiny tardigrades look like water bears. Although they are commonly found in water -- and at times, serving as the nemesis in "Ant-Man and the Wasp" -- tardigrades are known for their ability to survive and even thrive in the most extreme environments.
These tiny, pudgy animals are no longer than one millimeter. They have eight legs with claws at the end, a brain and central nervous system, and something sucker-like called a pharynx behind their mouth that can pierce food. Tardigrades are the smallest-known animal with legs.
All of these details are incredibly well preserved in the new fossil specimen, down to its tiny claws.
"The discovery of a fossil tardigrade is truly a once-in-a-generation event," said Phil Barden, senior author of the study and assistant professor of biology at New Jersey Institute of Technology, in a statement.
"What is so remarkable is that tardigrades are a ubiquitous ancient lineage that has seen it all on Earth, from the fall of the dinosaurs to the rise of terrestrial colonization of plants," Barden said. "Yet, they are like a ghost lineage for paleontologists with almost no fossil record. Finding any tardigrade fossil remains is an exciting moment where we can empirically see their progression through Earth history."
The fossil allowed researchers to see evolutionary aspects that aren't present in modern tardigrades, which means they can understand how they've changed over millions of years.
At first, the researchers didn't even notice the tardigrade was trapped in the piece of amber.