Sloths: South American Icons

Despite their rather minor status in modern times, the sloths were once a highly diverse and successful group of mammals. A part of the endemic South American order Xenarthra, sloths first emerge in the fossil record during the Early Oligocene but almost certainly diverged before this. Developing into browsing and grazing herbivores, an early lineage of sloths, the Megalocnids, successfully colonized the Caribbean and survived there until roughly 5000 years ago. All more derived sloths belong to two major clades: the Mylodontoids and the Megatherioids. Both of these lineages greatly diversified, with genera entering North America during the Late Miocene before the Great American Interchange. Some forms such as Megatherium and Eremotherium developed massive body sizes, weighing as much as modern elephants, while others took to the seas to exploit a boom in sea grasses. Despite possessing a range that covered the entirety of both American continents by the Pleistocene, the mainland ground sloths all died out by the Early Holocene c. 10,000 years ago. This was due to a mixture of climate change and human hunting, leave only two small arboreal genera to persist into modern times.
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[@vladimirlagos2688]

Also, worth mentioning, as an inhabitant of Central American, I can testify that there are quite a few examples of flora in here that coevolved to depend on giant Xenartrans that are barely surviving after the extinction of these wonderful creatures. It always gives me a strange sense of loss when I stumble upon one of these trees calling for a partner that is no longer there.

[@dr.polaris6423]

Great point! It’s a sad reminder of the lost megafauna of the Americas.

[@julioalbertoherrera1339]

Very clever comment, mastodons and sloths ate some kinds of tropical pumpkins 🎃🎃🎃. Actually some green and yellow smooth pumpkins, called *"squash"* in english, *"chilacayote"* in spanish (the word is náhuatl, or aztec language). At first glance, it looks like a watermelon.

[@bruceswinford4901]

We need to bring back ground sloths fr

[@bobsmith-jc9mj]

Avocados, mangos, and what else?

[@vladimirlagos2688]

@@bobsmith-jc9mj You are right on about avocados, but mangos actually were brought to America from the Phillipines by the Spanish. I don't know the names of these fruits in English, but some other local examples (listed with their local Spanish names) are zapotes, guacales, papayas, and about four or five more non-edible (to humans) fruits with big seeds that spring near the base of the trunk of thick trees. Some are artificially being kept around because they are considered ornamental, medicinal, or just plain exotic looking. And yes, pumpkins (there is a whole range of local pumpkins over here different from the one popular in the US) and squash. It is also believed a series of tubers (like yucas, and malangas) became toxic in their raw form to defend against giant xenartran diggers among other threats.

[@theicepickthatkilledtrotsk658]

In a more accurate Ice age movie, Sid would be the most dangerous of the group.

[@charlesthethomas8591]

Who said he already isn't

[@DISTurbedwaffle918]

Isn't he?

[@voodoojedizin4353]

I just read an article, about human footprints being found in white sands New Mexico. Being alongside a giant Sloth footprint trail. What was interesting were the footprints of children, that looked like they were playing in the water filled Sloth footprints. The article described them as children jumping up and down and splashing in the muddy footprints of the Sloth.

[@JaviBee]

thats amazing

[@PaleoAnalysis]

I love sloths, I actually did a video a while ago talking about different species of sloths and the possibility that some (like Thalassocnus) may have been hairless.

[@mhdfrb9971]

The giant sloth is like the equivalent of Therizinosaurus

[@dr.polaris6423]

Classic convergent evolution!

[@ecurewitz]

And chalicotheres, and gorillas

[@vladimirlagos2688]

Hands down the most thorough overview of the once great group of the sloths that I have ever found on KZbin. Awesome content as usual!

[@carolynallisee2463]

The body plan of the ancient ground sloths seems to be a favourite of Nature's. The combination of short tail and stocky back legs, barrel body, longer front legs, often armed with big, curved claws, and smallish head with teeth suited for munching leaves, has evolved several times, with some differences due to available plants and ancestral animal lines. There was Moschops and it's relatives, the Therizinosaurs, and Chalicotheres, as well as the ground sloths. And by pushing the body-plan boundaries abit, you could also include such creatures as some sauropod lines, gorillas and giraffe and okapis, too. All have their own slight differences, but same general shape. Perhaps, for a land living large bodied browser, Nature found the perfect set of characteristics...

[@brianzulauf2974]

Imagine a sloth dominated world where all mammals are related to basal sloths and they have diversified to fill every niche.

[@invisiblejaguar1]

An interesting addition to speculative evolution there

[@christosvoskresye]

Better yet, imagine a kaiju movie in which an enormous sloth emerges from the sea to destroy Tokyo -- very, very slowly.

[@petrfedor1851]

@@invisiblejaguar1 Serina but it was not canary but two toed sloth as the only terrestial verbates!

[@invisiblejaguar1]

@@petrfedor1851 that's the one!

[@brianzulauf2974]

@@invisiblejaguar1 imagine huminoid interdimesinal time traveling sloths that have advanced beyond computers and time.

[@deinowolfhybridhero5101]

It's wonderful how sloths (and Xenartrans in general) have occupied the most various ecological niches

[@bkjeong4302]

The really sad thing is that the vast majority of ground sloths actually did better during interglacials, so they would likely be MORE common today than during the last ice age if not for humans.

[@beastmaster0934]

Same could be said with many species of megafauna, especially in North America. Mastodons, Castoroidee, and many more actually relied on forests for their survival. So whenever an interglacial occurred, their populations would INCREASE in size.

[@bkjeong4302]

@@beastmaster0934 Exactly. We really cannot argue they got killed off by climatic factors.

[@rl9217]

I’d like to suggest a video idea on New Zealand’s extinct giant birds, like the haast eagle or moa. Extinct birds seem to get less coverage than most other groups of extinct creatures. And on the topic of birds, perhaps another idea being a video on the topic of the terror birds or Cuba’s predatory raptors? Good video I really like your content.

[@maxmustermann5271]

always happy to see a new upload from you ^^ I think mammal evolution is a vastly underappreciated topic, I'm glad you are there to fill that niche on yt

[@DoodersDen]

As someone whom was never really well versed when it comes to sloths in general, this video was such a treat!! I was barely even aware of the lineage and ecology of the milodontids, let alone all the other fascinating families and locals of these animals! Awesome video doc!

[@davidgusquiloor2665]

I remember the first time i heard sloths can swim i didn't believed it. It is very interesting how similar circunstances made all sloths extinct except the current ones that had a very speciallized niche.

[@ChicagoScorpion]

I know what you mean. I didn't know there were aquatic sloths til a couple of years earlier. I also found out there were at least a few species of carnivorous kangaroos....prehistoric times sure did have alot of diverse species of animals we already know today.

[@alextanasy4361]

Very interesting creatures, I would also love to see you do videos on the Dire Wolf, Short Faced Bear or The Terror Birds.

[@vjbele]

Been waiting for this one for a long time!

[@denderrant]

Fantastic video, and I am stoked for that Sebecid one coming up!!

[@benmcreynolds8581]

It's just facinating at how diverse this group of animals were. I could only imagine how well they could dig and scrape in caves. They probably tunneled really well. Ant eaters have insane claws and can easily gore a human or Jaguar if unlucky and get swatted by one of those ant eaters set of claws. Just imagine the type of potential and power some of these guys had? They have such strong skeleton structures. I can just Invision them being so tough and dense.

[@curledup]

Love your channel so much. Its so chill

[@thelaughinghyenas8465]

Thank you for the episode.

[@theprehistoricprofessor9076]

New subscriber here, I'm enjoying your content, both Prehistoric and Cryptid base! Enjoyed this video too and I can't wait for the next one!

[@kuitaranheatmorus9932]

Now this video was really awesome,so that's very nice to see,espically from a group of amazing prehistoric mammals

[@Flame-Bright-Cheer]

I literally love all of your videos this one especially but all the others as much as thank you for all your hard work you are very well spoken and interesting to listen to you

[@KGBZeka]

I really enjoyed the drawing at 16:37 with the penguins and seals down by the water.

[@vasantmasurekar4826]

Great video as always. I wish atleast 1 or 2 of these giant sloth species had survived till modern times and we could have seen them alive. What a sight it would be

[@douglasthescottishtwin3989]

10:01 Correction: Paramylodon inhabited a wide range stretching from Alberta in the north to Guatemala in the south.

[@gattycroc8073]

from herbivorous xenarthrans and meridiungulates to carnivorous sparassodonts, phorusrhacids, and sebecosuchians there should be a paleo project similar to Saurian or Prehistoric Planet that takes place in Cenozoic South America.

[@douglasthescottishtwin3989]

@@indyreno2933 Nasuina you mean

[@douglasthescottishtwin3989]

@@indyreno2933 Nasuina is a subgroup of Procyonidae.

[@douglasthescottishtwin3989]

@@indyreno2933 Have you got any source for this information?

[@douglasthescottishtwin3989]

@@indyreno2933 It's Nasuina, not Nasuidae.

[@douglasthescottishtwin3989]

@@indyreno2933 It's Nasuina not Nasuidae how many times am I going to have to tell you this?

[@JohnPaul_kun]

man I wonder what the wildlife would be like if these big sloths are still around today

[@jaynehorn151]

Absolutely fascinating.

[@George_M_]

"And then the humans ate them all" is the paleontology version of what "and then she was sent to be scrapped" for the stories of famous warships.

[@gamingindominus1049]

Hearing about the semi aquatic sloth bagged this question in my mind: what if sloths evolved to be more aquatic rather than arboreal, quite a interesting alternative evolution.

[@julioalbertoherrera1339]

I'm still not very convinced about marine sloths, but they have a point. Modern sloths are good swimmers. They swim very slooooowly but they are able to cross a river.

[@gamingindominus1049]

@@julioalbertoherrera1339 yes.

[@icecoldlow652]

Good commentary

[@RollandMcGriggs]

Dr. Polaris, I would like your educated opinion on ground sloths, please. For the sake of fun and curiosity, if a ground sloth was to be found with a population deep within the amazon rainforest, what ground sloth species would you say would be most plausible? I know you aren't a cryptozoology kind of person, and I understand why. But sometimes I think it's fun to entertain the idea. It's just that there have been accounts from natives in South America who say they've encountered large animals, roughly the size of a cow with reddish brown fur and four peg-like teeth in front of their regular teeth in the amazon. From my limited knowledge if it were possible, then they would have to be browsers to be able to live in a rainforest, right? Anyways, thanks for the effort and research that you put into your videos!

[@canis2020]

This is my spirit animal

[@robwalsh9843]

An animal that we now mock for being slow was once an animal that would make us cower like fearful little kids.

[@jonathanotero1987]

I suggested caribbean sloths a while ago now I want a video about Nesophontes (caribbean shrews)

[@PoshLifeforME]

"Do you want some sloth with your mammoth dear?" Is my suspicion for their decline.

[@jointgib]

really good

[@modelwiz2138]

Your content is awesome and packs a lot of interesting information not readily available elsewhere, but I wish you would omit the periodic booming sound running in the background of your videos. Very distracting when I am trying to absorb all the data.

[@Casmaniac]

Algorithm comment, this channel deserves a helluva lot more subs

[@GetToThePointAlready]

God i love that intro

[@adamhegedus5707]

What's the music you used for this video? I've noticed it in a bunch of your other videos, particularly those about animals from the Cenozoic, and it sets a pleasantly nostalgic mood no matter what you're talking about. It reminds me of The Jungle Book.

[@raghaviyer3065]

To me ground sloths are kind of terrifying

[@dr.polaris6423]

I agree in a way. You would certainly not want to anger them, as their claws and powerful forelimbs could rip through almost anything.

[@ecurewitz]

But also cool

[@azzman9947]

Yes another dr Polaris video

[@Captain_Gargoyle]

I never knew this was such a diverse lineage.

[@blackopal3138]

They are in Darwin, too. Saw it with my own eyes, in the open, it came out of a gully and crossed in front of me, about 15-20m. It was bigger than anything in this video, about the same as that dragon he visited. Same markings as the tree crocs here. I thought it was awesome, but had no idea I was seeing something so rare. It was 25 years ago, I knew monitors, but I remember thinking I didn't know they got that big. Must be in the north peninsula as well.

[@jessepitt]

I want some of what you are smoking.

[@blackopal3138]

@@jessepitt lol, oh, I see what you meant... do da do My god, could you imagine one of these crossing through a parking lot, lmao

[@robrice7246]

5:14 Would these types of sloths ever occupy the Florida Keys (and possibly mainland South Florida) not too long after that island chain formed (between 125 & 100,000 B.C.E.)? Or are there certain geographical barriers (such as the Gulf Stream) that prevent them from doing this (despite 9:43)?

[@dr.polaris6423]

I think they were only limited to the Caribbean, although they apparently never reached Jamaica either.

[@PaleoAnalysis]

@@dr.polaris6423 the only sloth species I'm aware of being found in Florida are Eremotherium, Paramylodon and Megalonyx. There may be others that I'm not aware of occuring here.

[@stevem.o.1185]

... you're thinking skunk ape too, aren't you? That swimming one looked so much like the famous picture from the everglades.

[@MikeWazowskixxx]

My idea is that Megatheriums & Eremotheriums in warm forests had thin fur like Cape buffalo, & in colder forests in North America, it was a bit thicker

[@Mint_P_Cane]

This funny british (bri’ish) polar bear is funny and educational

[@dr.polaris6423]

Why thank you 🙂

[@marcialjamaro6425]

Hello maybe we could get a new crypitds or unusual animal that be cool maybe like explain why u thing a crypitd is a real life animal love all your videos good doctor!!!!

[@keithprice475]

Yes, awesome content! I do though feel a bit like a broken record in pointing out that there is a THIRD explanation for the disappearance of SO MANY species, including ground sloths, at the end of the Pleistocene, and that it already has very solid evidence. I speak of course of the Younger Dryas Comet Impact Hypothesis. I will shower the first mainstream KZbin presenter to acknowledge it at all positively with effusive praise. Please be the first Dr Polaris!

[@DragonFae16]

Does anyone know why giant extinct ground sloths are all shown with long giraffe-like or anteater-like tongues? Is there evidence in the fossils of that?

[@davidguelette7036]

There are native populations in S.America that claim creatures resembling giant ground sloths still exist.

[@julioalbertoherrera1339]

Mapinguari. I read a book called *"Amazonas: Pleistocene Park"* written by an argentinian, *Luis Jorge Salinas.* He was a traveler in the late 70s and early 80s and he tells a very weird story. He arrived to Brazil and worked in a farm there. People there was very superstitious and believdd that in the night, there were "werewolves" _(lobizón)_ 🐺. He took a rifle and wanted to see the creatures himself. In a rural road, late at night, he saw a strange creature that he described as a _" walking gorilla with a dog's head"_ Reddish brown hair. He shot at one of these creatures, it seems that it was injured. But later he realized they were not dangerous or carnivorous and not "werewolves" and later he saw a whole herd of these creatures. He started a research, he concluded it was probably the creatures were *Megalonyx* survivors.

[@SteveWray]

I remember hearing about something described as the body of a tapir with the head of a jaguar. Maybe a surviving mesonychid :)

[@chpet1655]

I’m sceptical of the idea that humans wiped out all the large animal species. It just seems to me there weren’t enough people in any one area it has to be a possible contributor but I just can’t see it in every case.

[@sciencegeekgrandpa8]

Great video, as always. I now understand that the survival of juveniles must have been due to low reproductive rate and intensive parental care. But I still don't understand how they could manage with those hind feet....

[@kamion53]

@1:48 this depiction with the ground sloths having elephant like skin is probably more accurate then the tradional shaggy coated once. likely take from the modern sloths, but one cannot just "blow up"the beast with serious heat regulation problems. the first picture of a "naked"giant sloth I saw was dor by Marl Witton and it looked weird, this one does not look weird at all. @13:43 Would Thalasocnus not have a coat like a seaotter instead of the shaggy coat, the Pacific waters it lived in were probably then as cold as they are now.

[@differous01]

Myodon's osteoderms and the pangolin's external armour suggest a clade converging on the same strategy as armoured saurians: some glyptodons even evolved thagomizers.

[@dennismason3740]

Two miles from where I type is La Brea Park, an active bubbling tar pit where literally tens of thousands of critters died in the last million years. In the seventies you could sit right next to the dig and talk to the diggers. Now it's Disneyfied. The Pits are still bubbling away.

[@warrendargusch5873]

Mortal sin lives on!

[@gtprime2410]

1:57 Sid the Sloth in real size 😂

[@grandpa_puppet_69]

can you please do a video on desmostylians

[@douglasthescottishtwin3989]

Desmostylians are based

[@aaronlaluzerne6639]

Quite a size difference between old extinct sloths to the ones that are alive today.

[@bkjeong4302]

The extinct ones aren’t old. They were actually contemporaries of the living ones and only went extinct recently.

[@SteveWray]

Xenarthra are just weird. They remind me a lot of Australian marsupials. Their reproductive tracts seem kind of similar too.

[@robrice7246]

16:37/16:40 And watching out for everyone's favorite monster shark & Moby Dick during feeding trips.

[@denizen9998]

I saw the bones of huge sloths at the La Brea tar pits in Los Angeles. I forgot the species name.

[@eybaza6018]

Probably Megatherium

[@termitesc.aardwolf3644]

Is it bad I misread the title as South American lions?

[@ecurewitz]

Too bad we can’t resurrect these things and have a sort of Pleistocene Park

[@crisantinapangilinan8375]

South American sloth so huge how can it fit inside the truck or a car

[@spacewarsfight281]

The slow bois

[@greenkoopa]

*click the bell icon to receive all the latest videos!* I haven't been getting notified. My interests are on a wheel but the wheel has been stuck on ww2 for months. I'll be random and honest and say that the new star wars movies took away my interest in the franchise, I cant even enjoy KotoR anymore 🐢🐢🐢

[@petrfedor1851]

8:50 this doesn´t even sound that wierd, mylodon kinda look like someone try to draw bear out of memory and get distracted so it´s not suprising it might have comparable ecological niche.

[@jeroylenkins1745]

Who is Alexandra?

[@RA-dq4ro]

Did anyone else read south american lions?

[@indricotherium4802]

Well, personally, I would have named the two extant species the ten-toed sloth and the twelve-toed sloth. But who am I to challenge the logical perspectives of biologists?

[@luismiguelguevarahinojosa6662]

Sloth

[@Kurotitan7125]

Only in Ohio could ancient humans kill a giant ground sloth

[@scottmccrea1873]

With the exception of the island forms, it's preposterous to think that tiny numbers of humans armed w rocks & sticks systematically slaughtering dozens of gemera of sloths. Their size many & the osteoderms makes this farcical. Before agriculture, there just weren't enough people in the Americas to do this. Until the invention of high powered rifle cartiedges in the 1870s, whole sale slaughter of huge numbers of animals simply wasn't possible. Note - 2 toed sloths cannot swim!

[@nicelydunwell5681]

The good doctor is in! Prime candidate for de-extinction... easily domesticated, good for the ecosystem, but mostly bc I want to ride one!!!

[@cynthiajelsema968]

Seems kind of cruel for anything to weigh 4 tons, be a grazer and walk on your knuckles. 😬

[@nicksweeney5176]

Firrrrst...!!!

[@nicksweeney5176]

@LeoTheBritish-Eurasian I've spammed your mother; she likes it. It's time you come to terms with it all. Remember our bargain: You ignore me, I'll always ignore you. Kk, Flipper?😁👍🏻

[@markshort9098]

🏆

[@garcemac]

Nice thumbnail. Try harder.

[@eviljoel]

Nobody wants to see your fursona interrupt the video randomly. Why do you do this? What's the purpose?

[@chir0pter]

have to say i really hate the intro music. doesn't sound clear and also sounds like some creepy clown music. just saying