New Delhi: The discovery of a tooth fossil belonging to a capybara that lived in the Atacama Desert in northern Chile almost nine million years ago has stunned scientists. The finding not only provides the first and oldest record of a capybara in coastal Chile — a country where no capybaras live today — but it also calls into question the longstanding textbook version of the Atacama Desert being one of the oldest continuously dry regions on Earth, going back an estimated 40 million years, they said.
Native to South America, except Chile, capybara is the largest rodent and can be found living near water bodies due to its semi-aquatic lifestyle. The fossil, described in a paper published in the journal Scientific Reports, was found in a layer of sediments deposited in a shallow marine environment between 10 and seven million years ago, at a site called El Morro, the researchers said. El Morro is part of the fossil-rich Bahia Inglesa Formation, which also hosts Cerro Ballena, or “Whale Hill,” recognised as the world’s largest concentration of whale fossils.
“Finding a capybara tooth in a marine deposit in what today is one of the driest regions on Earth is just freakish,” lead author Priscilla Martinez, a doctoral student at the University of Arizona’s Department of Geosciences, said. The Andean mountain chain would have presented a formidable barrier jutting up to 18,000 feet, beginning long before capybaras appeared roughly nine million years ago, geologists have previously estimated. It effectively walled off the Atacama Desert from the eastern lowlands stretching across parts of Venezuela and Colombia down to northeastern Argentina and Uruguay, the animal’s current range, they said.
The researchers, however, proposed a scenario in which the capybaras took advantage of low-elevation wetlands connecting their original range along the coastal areas going “counterclockwise” around the northern portion of South America — from today’s Venezuela into Colombia, Ecuador and Peru, into northern Chile. “We have multiple lines of evidence indicative of really wet conditions that are typically associated with capybara today. The same deposits contain fossils of freshwater fishes and gavials (freshwater crocodiles),” co-author Mark Clementz, a paleobiology expert and head of the department of geology and geophysics at the University of Wyoming, US, said.
The team also unearthed phytoliths — microscopically small accumulations of silica forming inside plant cells and tissues as they absorb dissolved silica from groundwater through their roots — revealing evidence pointing to palms and other flowering plants, none of which would grow in the Atacama Desert of today, they said. “All this supports the idea that there was enough of an ecological community to support capybara populations long term,” Clementz added. No other remains of capybaras this old have been found in Chile to date, so finding a lone tooth within a three-foot-thick bed preserved in the desert that turned out to be the linchpin in this discovery was a miracle, according to Martinez. “Many of the fossils originally discovered at that location are lost in time, but certain merchants were interested in understanding them a little bit better, and so they donated them to local scientists,” Martinez said. Clementz added that the findings show it is worth challenging assumptions about the Atacama being an ancient desert for millions and millions of years.
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