In 16 million-year-old Dominican Amber, a new species of Tardigrade (Water Bear) has been discovered.

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Tardigrades, also known as water bears, are a diverse group of charismatic microscopic invertebrates that are best known for their ability to survive extreme conditions. A famous example was a 2007 trip to space where tardigrades were exposed to the space vacuum and harmful ionizing solar radiation, and still managed to survive and reproduce after returning to Earth. Tardigrades are found in all the continents of the world and in different environments including marine, freshwater, and terrestrial.

Tardigrades have survived all five Phanerozoic Great Mass Extinction events, yet the earliest modern-looking tardigrades are only known from the , approximately 80 million years ago. Despite their long evolutionary history and global distribution, the tardigrade fossil record is exceedingly sparse. Due to their microscopic size and non-biomineralizing body, the chance of tardigrades to become fossilized is small.

In a paper to be published on October 6, 2021, in Proceedings of the Royal Society B researchers describe a new modern-looking tardigrade fossil that represents a new genus and new species. The study used confocal laser microscopy to obtain higher resolution images of important anatomical characteristics that aid in phylogenetic analyses to establish the taxonomic placement of the fossil.

The new fossil Paradoryphoribius chronocaribbeus is only the third tardigrade amber fossil to be fully described and formally named to date. The other two fully described modern-looking tardigrade fossils are Milnesium swolenskyi and Beorn leggi, both known from Cretaceous-age amber in North America. Paradoryphoribius is the first fossil to be found embedded in Miocene (approximately 16 million years ago) Dominican amber and the first fossil representative of the tardigrade superfamily Isohypsibioidea.

Co-author Phillip Barden, , introduced the fossil to lead author Marc A. Mapalo, Ph.D. Candidate, and senior author Professor Javier Ortega-Hernández, both in the Department of Organismic and Evolutionary Biology, Harvard University. Barden’s lab discovered the fossil and teamed with Ortega-Hernández and Mapalo to analyze the fossil in detail. Mapalo, who specializes in tardigrades, took the lead in analyzing the fossil using confocal microscopes located in the Harvard Center for Biological Imaging.

“The difficulty of working with this amber specimen is that it’s far too small for dissecting microscopes, we needed a special microscope to fully see the fossil,” Mapalo said. Generally, the light transmitted by dissecting microscopes works well to reveal the morphology of larger inclusions such as insects and spiders in amber. Paradoryphoribius, however, has a total body length of only 559 micrometers, or slightly over half… Brinkwire News Summary.

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