How the sloth and cenote might have appeared 10,000 years ago How the sloth and cenote might have appeared 10,000 years ago. carmen rojas, inah

Giant sloth identified as a new species

Fossilized remains of 10,000-year-old animal have been pieced together

Experts have pieced together the fossilized remains of a giant sloth discovered in 2010 in a cenote, or sinkhole, in Quintana Roo and describe it as a new species.


The bones of the animal, estimated to have roamed the region more than 10,000 years ago, were not removed from the cenote until 2014. National Institute of Anthropology and History (INAH) underwater archaeologist Carmen Rojas Sandoval led a team that extracted the animal’s skull, its jawbone, nine vertebrae, three long bones, three ribs and seven claws.

Experts had to wait two years before the fossilized samples could be properly examined. During that time they had to transition from their freshwater cenote environment to one of distilled water. After that, a gradual dehydration process started in April 2015.

Specialists at the Mass Spectrometry Lab (Lema) at the National Autonomous University of Mexico (UNAM) were then able to carbon-date the sloth’s remains, concluding that it had lived between 10,647 and 10,305 years ago.

Direct observations made in the cenote at a depth of between 50 and 55 meters under water have concluded that the animal’s skeleton is mostly complete. This has led to the theory that the sloth fell into the cenote when it was dry, or mostly so.

The deepest recesses of the cenote started to fill up with water 10,000 years ago when Caribbean Sea levels started rising, a process that would completely submerge the network of caves in the Yucatán peninsula.

That same process allowed the “extraordinary conservation” of the sloth’s remains, as well as those of countless other mammals and humans that lived at the time in that part of the country. The sloth, nicknamed Pote for the cenote called Zapote in which it was found, is just one of 14 fossilized sloth remains found in 11 submerged caves so far.


A second expedition is scheduled for next year when INAH expects to retrieve the rest of Pote’s skeleton. The first expedition was funded by the institute, along with the Desert Museum of Coahuila, Heidelberg University in Germany and the Quintana Roo-based American Prehistory Institute.

The new species, Xibalbaonyx oviceps, has been named after the place it was found and its physical characteristics. Xibalba is the Maya term for the underworld, the interpretation given by that culture to the network of underwater caves that crisscrosses the Yucatán peninsula. Onyx is claw in Greek, while ovum describes the ovoid shape of the skull.

Mexico News Daily

  • sloth1
  • sloth2
  • sloth4
  • sloth3

Stories from our archives that you might enjoy

  • owl905

    Interesting article. 10,000 years ago was about half way through the sea-level rises that paralleled the meltdown of the great Laurentide Ice Sheet. The discovery not only retrieved a new species, but actually has some context about the habitat and factors that led to the bone bed.

  • Happy Girl

    Present day sloths are animals that spend most of their time in the forest canopy, coming down only to defecate…so the presence of these and other animals tells us a lot about the climate and the environment at the time. The artist’s rendering is terrible …such a bleak and uninhabitable desert scape with what I suppose are rocks but look like an ice field or crumpled sheets of paper blowing in the wind…but the sloth is o.k. The sloth most likely fell out of a tree surrounding the cenote. Even if these giant sloths lived on the forest floor they would have moved so slowly that they would have had time to turn around. Even now, 10,000 years later there is a forested area around the cenote.Time to send the artist back to the drawing board.