Swimming Ground Sloths

Posted by: Loren Coleman on August 8th, 2009

What if some South American “sea monster” stories were actually based on sea-going sloths? It is a wild idea, right?

From Peru, the discovery of these animals was first announced in May 1995, but have they swam under the sonar of most “sea cryptid” discussions?

The species, as suggested by this image, is certainly unique-looking. The animal is one that most people don’t even realize once existed.

Image used by permission of the artist, Bill Parsons.

“Ground sloths (Gravigrada, Xenarthra) are known from middle or late Oligocene to late Pleistocene in South America and from late Miocene to late Pleistocene in North America. They are medium to gigantic in size and have terrestrial habits. Discovery of abundant and well preserved remains of a new sloth (Thalassocnus natans), in marine Pliocene deposits from Peru drastically expands our knowledge of the range of adaptation of the order. The abundance of individuals, the absence of other land mammals in the rich marine vertebrate fauna of the site, and the fact that the Peruvian coast was a desert during the Pliocene suggest that it was living on the shore and entered the water probably to feed upon sea-grasses or seaweeds. The morphology of premaxillae, femur, caudal vertebrae (similar to those of otters and beavers) and limb proportions are in agreement with this interpretation.” [Nature 375, 224 – 227 (18 May 1995)] The research was reported by C. de Muizon and H. Greg McDonald in Nature.

In 2004, de Muizon, McDonald, Salas and Urbina reported on the evolution of the feeding strategy of the sloths: “The aquatic sloth Thalassocnus is represented by five species that lived along the coast of Peru from the late Miocene through the late Pliocene. A detailed comparison of the cranial and mandibular anatomy of these species indicates different feeding adaptations. The three older species of Thalassocnus (T. antiquus, T. natans, and T. littoralis) were probably partial grazers (intermediate or mixed feeders) and the transverse component of mandibular movement was very minor, if any. They were probably feeding partially on stranded sea weeds or sea grasses, or in very shallow waters (less than 1 m) as indicated by the abundant dental striae of their molariform teeth created by ingestion of sand. The two younger species (T. carolomartini and T. yaucensis) were more specialized grazers than the three older species and had a distinct transverse component in their mandibular movement. Their teeth almost totally lack dental striae. These two species were probably feeding exclusively in the water at a greater depth than the older species.” Journal of Vertebrate Paleontology: Vol. 24, No. 2, pp. 398–410.

Loren Coleman About Loren Coleman
Loren Coleman is one of the world’s leading cryptozoologists, some say “the” leading living cryptozoologist. Certainly, he is acknowledged as the current living American researcher and writer who has most popularized cryptozoology in the late 20th and early 21st centuries. Starting his fieldwork and investigations in 1960, after traveling and trekking extensively in pursuit of cryptozoological mysteries, Coleman began writing to share his experiences in 1969. An honorary member of Ivan T. Sanderson’s Society for the Investigation of the Unexplained in the 1970s, Coleman has been bestowed with similar honorary memberships of the North Idaho College Cryptozoology Club in 1983, and in subsequent years, that of the British Columbia Scientific Cryptozoology Club, CryptoSafari International, and other international organizations. He was also a Life Member and Benefactor of the International Society of Cryptozoology (now-defunct). Loren Coleman’s daily blog, as a member of the Cryptomundo Team, served as an ongoing avenue of communication for the ever-growing body of cryptozoo news from 2005 through 2013. He returned as an infrequent contributor beginning Halloween week of 2015. Coleman is the founder in 2003, and current director of the International Cryptozoology Museum in Portland, Maine.

7 Responses to “Swimming Ground Sloths”

  1. seandavis928 responds:

    I have seen video of sloths swimming, very strange looking moving so slow in the water. Never heard of the aquatic ground sloths before, very cool and creepy.

  2. Fhqwhgads responds:

    Interesting. It could explain a “horse-like head”. And maybe the Beast of Bray Road was a juvenile ground sloth; ground sloths seem to have been at least occasionally bipedal, and a young one might look somewhat wolf-like.

  3. CryptoInformant 2.0 responds:

    Wow – I didn’t even know that thing existed, to be honest. Pretty cool, and it would be interesting to find some that are still living.

  4. cryptidsrus responds:

    I’m willing to believe some of the sightings may indeed be these magnificent “sloths”—but not all of them.
    Were they strictly confined to tropical climates and/or South America?

    Because if they were, it would not necessarily explain their presence in colder, more northern climates, like Scotland or Vermont (i.e., Nessie and Champ).

    Most (not all) of the reports also describe an elongated, serpentine body—which is NOT quite what we see here.

    Like I said, may explain some but not all sightings.

    Good post as always, Loren. Thanks. Never knew these creatures existed.

  5. Fhqwhgads responds:

    According to Wikipedia, Megalonyx lived all the way up into Alaska. Taking into account that the climate is a good deal warmer than when the megafauna were alive (or prominent, if any survive), it seems unlikely that cold would be a serious problem for them.

    I’d like it if there were some surviving ground sloths, and there are a few sightings that could just possibly be sloths, but it’s really hard to see how a breeding population could survive without being discovered. Maybe sasquatch have the intelligence to remain hidden, but it’s unlikely ground sloths would see any point in hiding — the adults at least were too big for predators to risk a confrontation.

  6. shumway10973 responds:

    Never thought sloths would be fast enough to successfully swim under water and complete a task like eating. I have seen footage of a tree sloth swim a piranha infested pool and survived. The reason was because it moved so slow that unless it has an open wound, the piranhas think it is just a branch or something that’s not food. Some think that the lichen and such that regularly grow on most sloths might also have something to do with it, may even repulse the piranhas.

  7. Sordes responds:

    Some months ago I have seen a Thalassocnus skull at the NHM Karlsruhe, Germany. I was really amazed how small it was, only about the size of a medium sized dog. Ground sloths were not all giant monster, some of them were only very small.

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