Tardigrades are microscopic creatures notorious for surviving almost anything you can throw at them, but one thing they’re not good at is fossilizing. Now, an exceptionally well-preserved, “once-in-a-generation” tardigrade fossil has been found in a block of amber, and assigned to a new species and genus.
Tardigrades are positively adorable, even going by the cute nicknames of water bears or moss piglets, but don’t let that fool you – they’re extremely tough little critters. They’ve been known to handle extreme heat and cold, radiation, intense pressures at the bottom of the ocean, and even the vacuum of space. They’ve been revived after decades frozen, walked away after being fired from guns, and may live to see our Sun die in about five billion years’ time.
But there’s one hardship their little bodies don’t seem to stand up to – fossilization. In fact, only two examples are currently known in the fossil record. But now, researchers at Harvard and the New Jersey Institute of Technology have found a third, in a piece of 16-million-year-old amber found in the Dominican Republic. Funnily enough, the amber had already been well-studied but the tiny tardigrade went unnoticed for months.
“The discovery of a fossil tardigrade is truly a once-in-a-generation event,” says Phil Barden, senior author of a new study describing the find. “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. 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 newly-identified specimen measures about half a millimeter long, and is the best preserved example to date, allowing scientists to image tiny details right down to its claws and mouthparts. In doing so, they realized that it differed from living tardigrades so much that it was assigned not just as a new species but a new genus, Paradoryphoribius chronocaribbeus.
“At first glance, this fossil appears similar to modern tardigrades due to its relatively simple external morphology,” says Marc Mapalo, lead author of the study. “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. 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.”
The research was published in the journal Proceedings of the Royal Society B.