Indeed, similar megafauna were present in North America as well. The West Virginia state fossil is Megalonyx jeffersonii, a giant ground sloth present until the end of the Pleistocene. They're estimated to have been 10 feet "tall" and to weight roughly a ton. Fossil bones were discovered in Haynes Cave, Monroe County near the present day Virginia border, and the species is named for Thomas Jefferson, who examined bones and authored the paper that identified this genus. (Though the history of exactly which bones he identified is slightly murky.)
It seems likely that they were using these limestone caves for shelter, though it is also not uncommon for other Pleistocene fossils to be found and preserved in caves after washing in as sediment. I've never seen claw marks on cave walls quite large enough to attribute it to a ground sloth, but there are occasionally very large claw marks on cave walls... and I wouldn't want to be trapped in the dark with whatever creature left them behind.
Giant sloths was not really on my list of expected answers but
"One species, Glossotherium robustum, a
South American sloth that lived between 4 million and 12,500 years ago, reached more than
3 metres in length and weighed up to 1,500 kilograms"
> Giant sloths was not really on my list of expected answers
Despite not looking very alike at the first glance, sloths are grouped together with armadillos in the clade Xenarthra[1]. Both lineages descend from a common ancestor from around the time the dinosaurs went extinct. So it's not that surprising there were burrowing sloths. I guess the burrowing behaviour surely came handy to their shared ancestor by the time the dinosaurs were screwed by the asteroid that carved the Chicxulub crater[2]. What is mind-boggling for me is that once there were aquatic sloths[3]. Some sloths followed the steps from the ancestors of whales and dolphins, and rehearsed a return to sea. Unfortunately that evolutionary experiment was cut short when the gap between south and north america closed, isolating atlantic from pacific oceans and dooming the niche where the critters thrived. Had they persisted, I wonder if by now we could have whale-like sloths (whaloths?).
The giant sloth was the first thing that came to my mind. Nearly every time I'm at the grocery I think about the giant ground sloth theory of avocado evolution:
A number of authors, including Connie Barlow in her 2001 book The Ghosts of
Evolution, have speculated that the avocado is an "evolutionary anachronism"
with megafaunal dispersal syndrome (a concept originally proposed in the
1980s by Paul S. Martin and Daniel H. Janzen), arguing that the avocado
likely coevolved dispersal of its large seed by now-extinct megafauna. Barlow
proposed that the dispersers included the gomphothere (elephant relative)
Cuvieronius, as well as ground sloths, toxodontids, and glyptodonts. The
concept of evolutionary anachronisms/megafaunal dispersal syndrome has been
criticised by some authors, who note that many large fruit are readily
dispersed by non-megafaunal animals, with it being noted that living agoutis
disperse avocado seeds, with spectacled bears have also having been observed
eating domestic avocados.
My aunt has a big avocado tree in the north west of Argentina. The avocato are very small, probably an inch long. They are very tasty, but you must collect a lot of them to prepare a dish.
as is often the case, one species will make a burro only to have other species take over and modify it, with choice locations, used contiously for several millenia, so an odd scratch here and one there adds up, and we have no other behavioral evidence for this last mega fauna, so who knows?
might find more of these in different stages, with perhaps fossil evidence
I visited MOAS in Daytona last week, and learned about the ground sloth for the first time in my life. Fascinating. I thought I knew just about every animal to have lived on earth, but I was so wrong. Curious what other creatures like this I don't know about.
> The longest described so far is in Pará state in the Amazon region, with combined internal galleries some 1,500 metres long ...
I'm not a Mining Engineer, to know when CO2 accumulation would become a problem (if the giant sloths were living in the tunnels). But the effort needed to manually remove the tailings from a tunnel is O(n^2) - because the working face keeps getting further from the exit.
So as the article asks - how could the effort needed possibly be worthwhile?
Dig slightly up so CO2 doesn’t accumulate in low areas and spread the tunnels around like a tree or a mesh? Work with your fellow sloth team, take turns, dilly-dally around. What else would sloths do ;-)
Carving could have been done by natural processes, instead of creatures? Many large caves are created by simple process of chemical reactions and water flow over time. Any scratches on the surface could be from creatures.
From what I've read, these burrows have distinct claw marks ("claw-like markings on the walls") and structural patterns that don't match typical natural cave formation processes
In most of the western world it's illegal to excavate any significant volume without a bunch of permitting and oversight. Additional regulations surrounding living spaces. Plus the fact that you don't generally own the volume underneath your lot in the first place.
If you make it past all that (regardless of whether you selected the legal or illegal route) there's the expense of doing so safely. Then add on the expense of maintenance (by which I mostly mean water management).
Indeed, similar megafauna were present in North America as well. The West Virginia state fossil is Megalonyx jeffersonii, a giant ground sloth present until the end of the Pleistocene. They're estimated to have been 10 feet "tall" and to weight roughly a ton. Fossil bones were discovered in Haynes Cave, Monroe County near the present day Virginia border, and the species is named for Thomas Jefferson, who examined bones and authored the paper that identified this genus. (Though the history of exactly which bones he identified is slightly murky.)
https://en.wikipedia.org/wiki/Megalonyx
It seems likely that they were using these limestone caves for shelter, though it is also not uncommon for other Pleistocene fossils to be found and preserved in caves after washing in as sediment. I've never seen claw marks on cave walls quite large enough to attribute it to a ground sloth, but there are occasionally very large claw marks on cave walls... and I wouldn't want to be trapped in the dark with whatever creature left them behind.
The article at its source, Nature, with many more photos and a different title:
"Did giant ice age beasts carve these vast caves in South America?"
https://www.nature.com/articles/d41586-025-00216-x
The sheer size of these tunnels is mind-blowing
Giant sloths was not really on my list of expected answers but "One species, Glossotherium robustum, a South American sloth that lived between 4 million and 12,500 years ago, reached more than 3 metres in length and weighed up to 1,500 kilograms"
But who was really in charge?
> Giant sloths was not really on my list of expected answers
Despite not looking very alike at the first glance, sloths are grouped together with armadillos in the clade Xenarthra[1]. Both lineages descend from a common ancestor from around the time the dinosaurs went extinct. So it's not that surprising there were burrowing sloths. I guess the burrowing behaviour surely came handy to their shared ancestor by the time the dinosaurs were screwed by the asteroid that carved the Chicxulub crater[2]. What is mind-boggling for me is that once there were aquatic sloths[3]. Some sloths followed the steps from the ancestors of whales and dolphins, and rehearsed a return to sea. Unfortunately that evolutionary experiment was cut short when the gap between south and north america closed, isolating atlantic from pacific oceans and dooming the niche where the critters thrived. Had they persisted, I wonder if by now we could have whale-like sloths (whaloths?).
[1] https://en.wikipedia.org/wiki/Xenarthra
[2] https://en.wikipedia.org/wiki/Chicxulub_crater
[3] https://en.wikipedia.org/wiki/Thalassocnus
Manatees and dugongs feel like "whale-like sloths", though I have no idea if they're taxonomically related
They are more closely related to elephants.
Thank you for the aquatic sloth link, that's so cool!
The giant sloth was the first thing that came to my mind. Nearly every time I'm at the grocery I think about the giant ground sloth theory of avocado evolution:
https://en.wikipedia.org/wiki/Avocadohttps://link.springer.com/article/10.1007/BF02904012
Early wild avocado seeds were smaller at around 2cm/.8in in diameter.
My aunt has a big avocado tree in the north west of Argentina. The avocato are very small, probably an inch long. They are very tasty, but you must collect a lot of them to prepare a dish.
Glossotherium robustum looks quite chunky. There's a skeleton of one in the Natural History Museum London https://en.wikipedia.org/wiki/Glossotherium
and an artists impression https://static.wikia.nocookie.net/fossil/images/9/95/Reconst...
Good question, species do not put that much compulsive effort into preemptive escape without cause.
Thermal regulation is a possibility mentioned outside of predation.
Bears aren’t afraid of being eaten, but they still dig dens because they’re warm in the winter.
Maybe humans just used the claws of dead giant sloths to carve the caves for their own purposes.
Tunels are 100 millions year old. We split from chimps 5 millions years ago.
Modern humans are .11 million year old, and we arrived to America .015 million years ago.
No, what is 100 million years old is the rock layer. The tunnels are `recent`.
the sandstone formation is 100 million years old, not the tunnels
Just in time to kill the giants sloths?
as is often the case, one species will make a burro only to have other species take over and modify it, with choice locations, used contiously for several millenia, so an odd scratch here and one there adds up, and we have no other behavioral evidence for this last mega fauna, so who knows? might find more of these in different stages, with perhaps fossil evidence
Bruce Chatwin mentions the tunnels and sloths in his book "in Patagonia" 1977
I visited MOAS in Daytona last week, and learned about the ground sloth for the first time in my life. Fascinating. I thought I knew just about every animal to have lived on earth, but I was so wrong. Curious what other creatures like this I don't know about.
So not the Shrike?
I think they were carved by "the builders"...
> The longest described so far is in Pará state in the Amazon region, with combined internal galleries some 1,500 metres long ...
I'm not a Mining Engineer, to know when CO2 accumulation would become a problem (if the giant sloths were living in the tunnels). But the effort needed to manually remove the tailings from a tunnel is O(n^2) - because the working face keeps getting further from the exit.
So as the article asks - how could the effort needed possibly be worthwhile?
It appears to be combined lenght for the whole tunnel complex. Not 1,500 meters to the nearest exit.
Dig slightly up so CO2 doesn’t accumulate in low areas and spread the tunnels around like a tree or a mesh? Work with your fellow sloth team, take turns, dilly-dally around. What else would sloths do ;-)
How would the animal determine that the effort is no longer worthwhile?
I don't know. But pretty much every burrowing animal has to decide when the RoI has gotten too low to keep digging.
Do they use a spreadsheet?
No, a Burroughs mainframe.
Neural network.
Carving could have been done by natural processes, instead of creatures? Many large caves are created by simple process of chemical reactions and water flow over time. Any scratches on the surface could be from creatures.
From what I've read, these burrows have distinct claw marks ("claw-like markings on the walls") and structural patterns that don't match typical natural cave formation processes
I wish there were more pictures.
https://www.google.com/search?udm=2&q=paleoburrows
https://news.ycombinator.com/item?id=43083213
Since no one has said, but I strongly feel like it should be said and it's so great and positive abd triggers many memories.
Secret tunnel!
the irony is if it was some Stone Age counterpart to Seymour Cray
god I wish I could live in tunnels. like a hobbit. these sloths had it all figured out ...
https://discover.hubpages.com/living/The-Pitfalls-of-an-Unde... gets posted here every so often.
What's stoppin' ya?
In most of the western world it's illegal to excavate any significant volume without a bunch of permitting and oversight. Additional regulations surrounding living spaces. Plus the fact that you don't generally own the volume underneath your lot in the first place.
If you make it past all that (regardless of whether you selected the legal or illegal route) there's the expense of doing so safely. Then add on the expense of maintenance (by which I mostly mean water management).
government, money, local geology.
okay badger moles