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The last time I asked something similar, I asked if it would be possible for xenarthran mammals (armadillos, sloths and anteaters) to be thrown off of South America from life-giving rafts to other parts of the world. The possibility is very strong that they could survive the long treks across oceans. So the odds of armadillos and sloths colonizing other continents outside South America within the Paleocene-Eocene window are high.

But what of perhaps the most charismatic of South American mammals, the meridiungulates? If you've never heard of them, don't be disappointed. This clade died out during the Younger Dryas climate chaos 11,000 years ago. The meridiungulates were a group of hoofed mammals that were sister to the perissodactyls (horses, rhinos and tapirs) but were strictly original to the island continent of South America, which no longer became an island when Panama connected North to South as recently as the late Pliocene epoch some three million years ago. They ruled South America from the Paleocene all the way to the Pleistocene, their reign undone by a combination of climate change and competition from northern hemisphere ungulates.

But what makes the meridiungulates particularly interesting is that not all of them lived their lives like the other hoofed mammals. Some of them were small enough to look and act like rabbits!

So within the Paleocene-Eocene window (59-36 million years ago), would it be possible for some of those small, rabbit-like meridiungulates to get rafted out of South America and eventually land on other parts of the world (preferably North America, Africa or both)?

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  • $\begingroup$ If they were rabbit-like, I'd vote "yes possible". But the picture on Wikipedia doesn't lend much credence to your theory... they weren't climbers/graspers, and rafting across an ocean for that proto-rhino seems far-fetched even considering you'd only need a single event over spans of millions of years. $\endgroup$
    – John O
    Apr 23 '20 at 21:39
  • $\begingroup$ @JohnO What picture? $\endgroup$ Apr 23 '20 at 23:44
  • $\begingroup$ I suspect this one $\endgroup$ Apr 24 '20 at 5:29
  • $\begingroup$ That wasn't a Paleocene specimen. $\endgroup$ Apr 24 '20 at 11:45
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Wikipedia says

Most Meridiungulata died out following the invasion of South America by North American ungulates and predators during the Great American Interchange

Which makes it plausible to say: they didn't manage to survive in the environment they were the best adapted to, it's likely that any adventurer that reached (by whatever means) the North America shores most likely died without leaving offspring. That is: even if they did, the results are inconsequential for the species/biomes evolution.

This, to my mind, means: if you plan to write a saga about Meridiungulata heroic adventurers during pre-"Great American Interchange" times, it's safe to do so as long as the books in your saga don't end with "and they lived happily ever after"; we see no evidence of them today, very likely they ended - flesh, bones and hooves - as food.

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  • $\begingroup$ I'm afraid I don't follow. $\endgroup$ Apr 24 '20 at 11:45
  • $\begingroup$ @JohnWDailey If "some of those small, rabbit-like meridiungulates did not get rafted out of South America" but you need them to have done it in the interest of your story, make it happen anyway. Just make sure your story is not about a successful evolution of the species at destination, because in reality they likely failed at it. $\endgroup$ Apr 24 '20 at 12:00
  • $\begingroup$ World comes before history, and history comes before story. That is the reality of things. $\endgroup$ Apr 24 '20 at 12:56
  • $\begingroup$ @JohnWDailey well, in an alternate-history context, it may have happen, so an alternate history story is allowed to contain it. The reality-check doesn't show such a thing have happened, it's an indication (but not a proof) that in our history may have not happened. $\endgroup$ Apr 24 '20 at 13:54

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