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Hidden in plain sight, the third tardigrade fossil on record has been found suspended in a 16-million-year-old piece of Dominican amber.
The find includes a newly named species, Paradoryphoribius chronocaribbeus, as a relative of the modern tardigrade family known as Isohypsibioidea. It is the first tardigrade fossil of the Cenozoic, our current geological era that began 66 million years ago.
Under a microscope, tiny tardigrades look like water bears. Although they are commonly found in water – and sometimes, serving as an enemy in “Ant-Man and the Wasp” – tardigrades are known for their ability to survive and even thrive in the most extreme environments.
These plump little animals measure no more than a millimeter. They have eight legs with claws at the end, a brain and central nervous system, and something sucker-like called a pharynx behind the 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, right down to its tiny claws.
“The discovery of a fossil tardigrade is truly a once-in-a-generation event,” said Phil Barden, lead author of the study and assistant professor of biology at the New Jersey Institute of Technology, in a statement.
“What is so remarkable is that tardigrades are an ancient ubiquitous lineage that has seen everything on Earth from the fall of dinosaurs to the rise of terrestrial colonization of plants,” Barden said. “Yet they are like a ghost line to paleontologists with almost no fossil record. Finding the remains of tardigrade fossils is an exciting time where we can empirically see their progression through Earth’s history.”
The fossil allowed researchers to see evolutionary aspects that are not present in modern tardigrades, meaning they can understand how they have changed over millions of years.
At first, the researchers didn’t even notice that the tardigrade was trapped in the piece of amber.
“It’s a slight dot in the amber,” Barden said. “In fact, Pdo. Chronocaribbeus was originally an inclusion hidden in the corner of a piece of amber with three different ant species that our lab had studied, and it hasn’t been spotted for months.”
Extensive observational analysis helped researchers determine where the new species belongs in the tardigrade family tree.
“The fact that we have had to rely on imaging techniques usually reserved for cell and molecular biology shows how difficult it is to study fossil tardigrades,” said Javier Ortega-Hernández, co-author of the ‘study and assistant professor of biological and evolutionary biology at Harvard University, in a statement. “We hope this work will encourage our colleagues to take a closer look at their amber samples with similar techniques to better understand these cryptic organisms.”
The new species is the first definitive fossil of the modern tardigrade family Isohypsibioidea found today in marine and terrestrial environments.
“We are only scratching the surface when it comes to understanding living Lateigrade communities, especially in places like the Caribbean where they have not been studied,” Barden said. “This study is a reminder that as little as we can get any tardigrade fossils, we also know very little about the living species on our planet today.”
Tiny animals are related to arthropods and have a deep origin during the Cambrian Explosion, when several species of animals suddenly appear in Earth’s fossil record 541 million years ago. Other tardigrade fossils could be lurking in other pieces of amber that have already been studied – researchers just need to look closely enough and have the expertise of what they are looking for when it comes to microscopic fossils.
And tardigrades could outlive humans. This is because they would largely not be affected by things that could potentially be fatal to Earth and human life in the future, such as asteroids, supernovae, or gamma ray bursts. Until the world’s oceans evaporate, tardigrades will live.
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