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Hyraxes are furry potatoes that look a lot like rodents, but at the mammal family reunion, you won’t find them sitting by the groundhogs and chinchillas. Instead, their actual cousins are elephants and sea cows…and we’re not sure which is closer.

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Sources:
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Images:
https://docs.google.com/document/d/1IJ4Bxw9ElN6XsVN6sPp3kgka7G0Wt5SPwAmI0EUma6U/edit?usp=sharing
This furry potato looks an  awful lot like a rodent.

It’s got the general size and  shape of your typical marmot. It has incisors that keep  growing for its entire life,   like a rodent.

And heck, could those whiskers lie? But at the mammal family reunion,   you won’t find the hyrax sitting by the  groundhogs and chinchillas of the world. Instead, its closest relatives hint at something  much weirder going on in its evolutionary history.

Because, its actual cousins  are elephants and sea cows… and we’re not sure which is closer. [ ♪♪ INTRO ♪♪ ] If you want to support the channel,   the Bizarre Beasts pin club is open  for subscriptions for the whole month! Sign up by June 20th and the first  pin you will get will be one of these incredible fuzzy potatoes. And stick around for the end of the  video for some bonus hyrax facts.

There are six or seven extant species  of hyraxes, depending on who you ask,   and they can be found in the Middle  East and throughout much of Africa. They may look cute, but they  can sound truly horrible. [Hyrax Noises] Some hyrax species are solitary and live in trees,   while others live socially  in groups on rock outcrops. And like a lot of animals their size,  they eat plants and bugs.

So far, nothing really out of the ordinary here. But before we get into their bizarre family tree,   we gotta say that hyraxes have some  noteworthy weirdness all their own. As a diurnal species, they can  often be found basking in the sun… But this isn’t just a comfort thing: they’re actually not great at regulating  their internal body temperature,   so they need that extra solar boost to stay warm.

Luckily, they have an easy  time climbing and clinging   to nice sunny spots thanks  to their suction cup feet! The muscular structure of their  foot pads combined with some fancy   gland secretions help them grip onto  surprisingly steep and smooth surfaces. Hyraxes also don’t eat like most other animals.

Their front teeth may at first glance look  like the gnawing incisors used by rodents,   but they’re actually simple tusks  used for displays and for grooming. So they have to turn their heads  sideways to bite with their molars – teeth that scientists at one point thought more  closely resembled those of rhinos and horses – and then chew normally. From there, things go right back to strange  again when the food makes its way into their   unique multi-chambered digestive system  that ferments with the help of microbes,   a lot like in cows and other ruminants.

But unlike true ruminants, hyraxes don’t  regurgitate a cud to continue chewing – their digestive system is one-way. And because they live in such dry habitats,   hyraxes also have pretty efficient  kidneys that help them conserve water. This means that their urine is extra  concentrated when nature finally calls,   and it quickly dries into  something resembling molasses.

Social hyrax species often use middens,  effectively common bathroom mounds,   to do their business, creating mountains  of pee crystals that fossilize over time. And fossilized hyrax waste  is so abundant and unique   that it even gets its own special mineral name: hyraceum. Fossilization of this thick, quick-drying  urine can also capture environmental data,   like atmospheric radioisotopes  and airborne pollen – you can think of it as a less glamorous  version of the “insect in amber” effect.

So while colder regions can use ice cores as  time capsules for studying climate change,   South Africa gets to use huge  piles of fossilized hyrax pee. All of that is weird and wild enough,   but let’s get back to the common  ancestor of the elephant in the room: what is the deal with hyrax taxonomy? They look like rodents.

They digest sort of like ruminants. They chew with teeth like horses’. They have incisors that are kinda like tusks.

So where in the mammal family tree do they fit in? By looking at bones and later at proteins,  scientists have concluded that hyraxes   belong in a clade called Paenungulata, literally “almost ungulates”. This group is comprised of  the orders Proboscidea (elephants), Sirenia (manatees and dugongs), and Hyracoidea (our friends, the hyraxes).

The Paenungulates likely arose  roughly 65 million years ago,   when mammals really started to go  nuts after the dinosaurs were gone. And although grouping these three orders together  has been pretty agreed upon since the mid-20th century,  figuring out how exactly each order  is related to the other two has been messy. Comparisons using anatomy, amino acids,   and different gene sets have  each given contradictory answers.

Even with the help of increasingly  sophisticated DNA tools, we still don’t   have a totally clear answer as to which  of the three orders branched off when – in other words, between hyraxes, elephants, and sea cows,    we still can’t really  tell who’s more closely related to whom. Right now, there is basically equal molecular evidence supporting any of the  three possible arrangements… Hyracoidea could have split off  first from Proboscidea and Sirenia,   Sirenia could be an outgroup  to Proboscidea and Hyracoidea,   or Hyracoidea and Sirenia could be more closely  related to each other than to Proboscidea. And the persistence of this uncertainty makes it   very possible that this specific  case is an example of a polytomy.

A polytomy is when speciation occurs not as a  two-way branching event on a phylogenetic tree,   but as a simultaneous branching of three or  more species from the same common ancestor. Usually this is simply a placeholder in an  evolutionary tree until we can figure out   which species branched off first, which  is a scenario called a “soft polytomy.” But it is possible for a  three-way species radiation to be,   for all intents and purposes, truly simultaneous – or, a “hard polytomy.” And chromosomal evidence suggests that  radiation among the Paenungulata orders   took 4 to 7 million years, and the  latest genetic analyses suggest   that this radiation began from an  honest-to-goodness hard polytomy. So hyraxes don’t just have surprising relatives: their speciation represents a rare  evolutionary occurrence as well!

And to cap it off, according to some researchers,   these screaming teddy bears may  also have an aquatic background. Red blood cells contain the protein hemoglobin,   which transports oxygen and  iron throughout the body. Muscles contain a similar  molecule called myoglobin,   and animals that dive deep underwater and  hold their breath for a long time tend to   have high concentrations of extra-positively  charged myoglobin molecules in their muscles.

The positive charge causes the molecules to  repel each other, allowing myoglobins to be   highly concentrated in the muscles without  sticking together and becoming useless. And this extra myoglobin helps  diving animals maximize their   oxygen usage until they can get another breath. Hyraxes and elephants have this  same telltale pattern of more   myoglobin than most terrestrial animals and  extra-charged myoglobin in their muscles.

It’s not as extreme as it  is in, say, modern whales,   but it is significantly higher than in species  with strictly terrestrial mammal ancestors. Because scientists have yet to pinpoint the  exact nature of the evolutionary branching   of the Paenungulates, we can’t say for sure  who this past aquatic common ancestor was. But all signs point to Proboscideans,  Sirenians, and Hyracoideans descending   from one of the earliest known placental  mammals to become underwater specialists.

You might see a weird, rock-hopping,  guinea pig-looking critter today,   but appearances alone don’t tell a fraction  of the long and storied history in play here. So the evidence is in! Hyraxes definitely  are not rodents, and definitely are the way-cool descendants of a common, possibly  aquatic, ancestor of elephants and sea cows.

And their superficial similarities to rodents  can be chalked up to convergent evolution – occupy the same ecological niche long enough,   and you’ll eventually end up with unrelated  species who share similar adaptations. The confusion about the hyrax’s  lineage is a reminder that taxonomy,   for all its structure and rules,  is at the end of the day a human construct. We love to understand the world around us,  what things are, and where they come from,   but our tools for answering these  questions always have limits.

And as those tools become increasingly  sophisticated, we can potentially solve   more of these evolutionary mysteries, making  beasts like the hyrax seem less bizarre to us. Don’t forget to sign up for the  pin club at BizarreBeastsShow.com   by June 20th if you want one of  these little potato-guy pins. And now for some bonus facts… [ ♪♪ BONUS FACTS ♪♪ ] Okay, hyraxes are just so weird that  we couldn’t fit all their weirdness   into the main part of the video, so  here are a couple of bonus facts: We mentioned that hyraxes aren’t great at  regulating their own body temperatures, so   along with basking in the sun, rock hyraxes will  also do a behavior called ‘heaping’ to keep warm.

And that’s pretty much  exactly what it sounds like. The hyraxes will pile themselves  together in a furry little stack   in their den to conserve body heat,  which sounds adorable, to be honest. Hyraxes also have relatively long  gestation periods for mammals of   their size, something like six to eight months.

And it’s been suggested that  this is just an evolutionary   leftover from their ancestors,  many of whom were much bigger – up to rhino-sized! [ ♪♪ OUTRO♪♪ ]