How Vertebrates Got Teeth... And Lost Them Again 

It is extremely interesting that Mammals are the only lineage of tetrapod to develop ear pinna (the outer ear). I would love for a video on this as well!

@@horse14t yeah and if it has any evolutionary advantage for us

@@andrearivera1622 Well it does have purposes as Ear Pinna can serve to filter sounds better into our ear canals for better hearing and in most other mammals apart from many primates including us and some other mammals; communication purposes and a warning system. The position of say a dog or cat's pinna can very clearly tell you how they are feeling or what they are listening to without them having to vocalize it. Additionally having the ability to swivel your ear to listen in on sounds of interest without having to move your head, body or neck is a huge advantage when listening out for predators or other animals that may want to harm or eat you. Now that I think about it perhaps Ear Pinna evolved in tandem to the evolution of the more complex mammalian ear 🤔

IIRC, owls have feather structures that help guide sound into their ears, though not the type of outer ear that mammals have.

Outer ears wouldn't really show up in the fossil record often. They are not made of bone. It's made of cartilage (I believe) and wouldn't fossilize or be preserved well.

I would love to learn more about the teeth on skin option too!

sharks have dentin scales! unfortunately i don't know much more than that basic fact, but it might be a cool thing to research :)

Dentin scales are very hard and have ridges on them (going from head to tail), allowing for increased defense and aerodynamics in sharks

i’m gonna wow at parties when i say this instead of “the chicken or the egg”

I'd imagine, if it was skin teeth to mouth teeth we'd have animals around today that have skin teeth. Instead I think this fish is an outlier

@@Stevie-J @Ryan Colligan Also the Toothless Toads

As is her passion for bad jokes. 😂

What are her squirtistics

her voice too

So much better than the painted lady

@@stevenkanzler2319 - Love them both!

Except for egg teeth?😜 Are the beaks of baby birds too soft to make it out of the shell?🤷‍

I heard that the loss of teeth in birds was a weight-saving device. Beaks are a lot lighter than jaws.

@@icollectstories5702 typically, yes. The newborn bill is more like cartilage than bone in terms of "squishiness". Having an egg tooth helps zip open a hardshelled egg. Its also not a real tooth, but more of an extra hard nub at the tip of the bill- or nose, if youre a reptile. Snakes have one too! I'm not sure about other reptiles but I'm sure if snakes and birds have them, the others also must

@@kitgodsey monotremes have em too

You should watch the video named When Birds Had Teeth too.

Hmm yeah it has been found that theory is not true.

I mean it hurts enough biting your tongue while chewing - can't imagine impaling it while sling shotting it. No wonder they evolved to be toothless.

I want an adapted game of rock paper scissors. But I think rock still beats ballistic tongue.

@@Cat_Woods tounge wets paper, that's all I got.

@@benhalpin7306 LOL

@@Stevie-J something about this doesn't add up. Tounge is very much under powered. There needs to be a 5th element. The interesting thing is though, that tounge vs tounge isn't just a draw it's very sexual.

Its tricky because fossils for land arthropods are the same as aquatic ones. (Legs and lungs already were a thing). "foot"print evidence is the earliest known evidence of arthropods on land.

I was actually looking at this question a few weeks ago. There are three main groups of terrestrial arthropods are myriapodia (centipedes and millipedes), arachnids (spiders, scorpions, ticks, mites, and others), and hexapoda (insects and "wingless insects"). A few other arthropods are terrestrial, but those are the three main groups and by far the oldest.

From my limited understanding of arthropod taxonomy, I think with insects the idea is that wingless insects like springtails were likely the first to arise, as they live in incredibly damp environments even when terrestrial, and then they diversified from there. I really dont know much about bug evo though, lol

I don't know but ... crabs look like giant spiders to me and crayfish look like baby lobsters. The movement to land was either coastal like crabs to spiders (just hanging out on the beach for longer and farther inland) or moving upstream (salt water to freshwater first) like lobster to crayfish and then colonizing interior. Darn cool question.

The existing land lineages are so far apart that it is unlikely that they had a terrestrial common ancenstor. Their LCA was probably before land plants and terrestrial life was possible. So most likely independent movements to land.

I'd also assume that calcium may sometimes play a role.

But if your beak got broken, would it heal before you starved? I'd imagine a jaw would be easier to heal.

@@icollectstories5702 I just imagined beaks made of dentine... Curse you, lmao

@@icollectstories5702 a tooth never heals

@@parthbonde2106 But, depending on the animal, it gets replaced

I second this!

Insects? Arthropods appear on land 419 MYA, before insects evolved.

Inside the walking fish

@@AndrewTBP Pedantry doesn’t make you look smart nor cool, you knew what OP meant

That's probably straight up wrong. Why would animals ever wander out of the sea if they have nothing to eat onshore? Escaping predators might be a thing, but that's hardly enough to develop a whole new breathing system. Animals should have been very busy on land to develop such adaptation.

​@@hellstorm300 insects

Pretty sure beaks can get infected too. And being that they only have one, it's a huuuuge problem if that does happen, or if a bird loses any part of their beak

@@StonedtotheBones13 yeah but a beak is overall more sturdy

@@stanpines9011 I never said it was or wasn't. I said they can definitely get infected. Next time you rush to correct someone, maybe make sure you're actually correcting the right thing.

@@StonedtotheBones13 Yeah but by chance is way more easy to infect teeth, in the great game beaks are more stable, more difficult to be damaged and thus it can be more reliable

😂

Did she grow a beak, too?

Ukoppoiu Kbpllljjjhkkkklkklppp00 J6opllppploôi9

@@vangmua3260 What

Angiosperms vs gymnosperms.

Yeah. What could go wrong with having a relatively big ballistic tongue shooting back into a mouth of sharp teeth?

I read they managed to do it to a chicken embryo a few years ago, the chicken starting to produce alligator-like teeth.

"Life... uh.. finds a way. " - Some guy in a movie from the 90's.

Check out the Stephen King short story "Rainy Season" ;)

Southeast asia has fang frogs.

Mammals : You gotta spend money to get money.

Someone tell the squirrels to not put so much into tooth regeneration!

It's like VCR

​@@naamadossantossilva4736 Meanwhile, 400 million years later... Humans: *eating the pizza diet* Meh, are teeth REALLY necessary? We just need softer pizzas...

@@Zaxares and bigger beards to hide the weak jaws

And how all mammals have atleast basic night vision

@@onyxgrnr666 And lost some color vision with that, but primates re-evolved a third cone, losing some night-vision in the process for most of them ^^

How would teeth help them swallow?

@@Cillana from what I've seen, the eyeballs of frogs sorta push the food down their throat. The projectile tongue occupies most of the skull and only while eating the frog closes its eyes to push the food down.

@@adityamohan1773 Yes, I know. I'm asking what do teeth have to do with swallowing.

@@Cillana in reptiles for an example teeth/fangs help in pushing the food back into the mouth.

@@adityamohan1773 okay 👍 thanks for answering Edit: I have seen video where frogs use their hands to shove food in their mouth. Then they use their eyes to swallow.

I remember reading something a while back that said that the reason us mammals don't have beaks is due to the fact that we have to drink milk as infants, and if you had a beak, you can't make the sucking motion that's required to drink milk. So basically the reason us mammals never evolved beaks is because we suck. Platypus get away with a beak because the mothers sweat milk

I think 1 of the reasons why mammals in general have not lost its teeth are that the mammalian teeth is more moldable than the sauropsid teeth.

I think to answer this you have to go back to our therapsid ancestors one of the defining characteristics of cynodonts is anatomical changes to the structure of jaws which granted them the ability to chew. Chewing is a unique adaptation to Cynodonts and all their living descendants offering one of the most effective ways of predigesting food. No other vertebrate group is capable of chewing their food they instead rely on tripping tearing and or slicing food into smaller pieces, with the closest analog seeming to be gizzards of birds at least among extant animals. In this sense chewing adapted jaws are a powerful evolutionary advantage which largely necessitates the preservation of teeth and the ability to produce enamel. From the fossil record we can see that our ancestors and their cousins in fact convergently further specialized their jaws and teeth for better filling this ecological role such as by reducing the jaw bones over time through repeated secondary losses or repurposing as those bones were adapted to build the mammalian ear and analogous ears of close synapsid cousins. In effect the jaws and teeth of mammals are our evolutionary lineages most defining characteristic dating back to our Permian therapsid ancestors. Beaks while versatile are unable to be used to perform similar roles as beaks but can conversely perform most of the same functions which make beaks successful so from an evolutionary perspective switching from mammalian chewing jaws to beaks would require adapting to an increasingly different mode of lifestyle which would only be an option if there was an open ecological niche that provided an opportunity to do so. In this sense the competition from archosaurs and to a lesser extent dicynodonts was probably one of the main limitations that locked cynodont descendants into the chewing mode lifestyle as it allowed them to exploit food sources archosaurs couldn't allowing them to persist despite having a vastly inferior respiratory system compared to archosaurs. Basically mammalian jaws and teeth adapted for chewing were probably the defining traits that allowed cynodonts and their descendants to avoid getting out competed by archosaurs. Then when the archosaurs either went extinct or became so specialized they were no longer in direct competition and the few mammals that survived were finally able to diversify and so we see mammals start to experiment more giving us stuff which fills now vacant niches such as baleen whales. Beaked mammals however would still have to compete with chewing mammals and beaked birds which would put them at an evolutionary disadvantage without some similarly impressive adaptations.

The platypus _is_ a mammal, a monotreme. It doesn’t have a beak like birds do, the bill is fleshy and flexible.

Beaks and tongues may have beaten teeth but we're still the ones eating chicken and frog legs, not the other way around. Certain traits do not pair well with others. As noted, lactation and beaks don't work well. It's possible that teeth end up having some hidden advantage for certain lifestyles and diets. It's hard to be an apex predator without teeth, for example.

Oh! They already did this one! Look up PBS Eons: Where are all the Mid Sized Dinosaurs?

ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-YXe9IHVX17U.html think you mean this video? It's about mid sized dinosaurs.

This missing ones are the ones that got eaten. It's a race to get big enough so you are too big to be predated. If you don't make it, you get torn to pieces and wind up in somebody's stomach.

@@dingfeldersmurfalot4560 but even when they get eaten we can still find fossils- also idk if its true i just want them to do a vid on it lol

@@dingfeldersmurfalot4560 you would still find the bones tho...

you do know all of this is just guesswork, right? we dont know any of this as fact

@@fingersmcoy at any point did i state it was factual? actually no, i did not. i was complimenting eons and this will be my only response to you. check yourself homie

Yeah. I want my beak genes back.

I agree. Check out the Dollo's law of irreversibility. In birds that circumstances when they need something to grasp using their mouth, they never evolved teeth, instead to evolved keratin parts that act like teeth in their beaks.

I don’t think building nests is a trait that gets evolved, it seems more like an adapted behavior than a genetic trait, don’t u think? Or did u just mean how they started building nests and not necessarily how they “evolved?”

I think its hard to get fossil record of nests

For the time IG…

Normal for PBS Eons. They have a video on the sea scorpions. The largest arthropods ever.

They're not teeths stricto-sensu, because they're not made of dentine, but of keratine, as the rest of the beak. But yeah, they have teeth-like structures, and they even have other teeth-like structures on their tongues (a close-up look on a geese mouth is terrifying XD). Although it may hurt, they're not meant to bite, but to filtrate water, just like the baleens of a whale. Baleens are not teeths either (although primitive whales and some seals do use teeths to filtrate water), they're made in keratine and support hairs).

I was just about to say that! Geese are terrifying!

I think that what they have is called tomial teeth.

Evolution has no direction. So perhaps there will eventually be descendants with no teeth, shorter tongues, or both -- or no descendants at all. I'd be interested to know how they avoid biting their tongues, or if they heal quickly. Perhaps they learn tongue coordination well as younglings.

@@icollectstories5702 If you watch chameleons videos, they do everything slowly, even chewing their prey once caught, I guess they never really bite their tongue because they're very cautious ^^

My one eyed Toad struggles to eat certain things such as Worms because they use their eyes to create suction to swallow.

yes. Sturgeon have no teeth, for example.

Parrotfish as well. And I'm not sure, but I think Catfish don't have teeth either. They just kinds inhale their prey

@@rowanmelton7643 Yeah suction feeders, those that rapidly open their mouths casing water to rush in to fill the void sucking in hapless prey within that water generally lose their teeth which makes sense since teeth would produce added drag to lower the effectiveness of suction feeding.

Also as another fossil example if I remember correctly some of the heavily armored Placoderms also lost their teeth developing wicked looking crushing bladed beaklike protrusions on their heavily armored skulls. We have even found some early placoderms with teeth and their vicious built in armored jaws so it too fits the trend of coexistence before eventual teeth replacement.

@@rowanmelton7643 I think catfish still do have some teeth. There might be completely toothless variants, but I'm pretty sure that most catfish species do still have vestigial teeth.

They are tetrapods, so yes. They shared a commmon ancestor with dinosaurs. For most of their evolution, pterosaurs had beaks. It wasn't until the latter part of the Cretaceous that toothlesness became the norm.

Eyes have evolved multiple times in different lineages, might be too broad for just one video.

@@mboatrightED300 Though that fact makes it even more worth to talk about

Have they not talked about that yet? Shoot, I'll second this one.

Glad to hear you like Chanel, I prefer Gucci myself

@@curiodyssey3867 bruh

I think if teeth were so much worse than beaks, they wouldnt have survived up to today. They probably are just less suitable that beaks for some things. And it can happen relatively easily that a animal evolves a beak to adapt to a new environment compared to how rarely it will happen to evolve back from beaks to teeth. (So basically, for some animaly teeth would nowadays probably be better than beaks but evolution doesnt go backwards so they keep their beaks and at most develop some tooth-like things in their beaks)

Yes, but they do have specialist beak-doctors.

Wow that was tough to read

1) from vibration sensors useful in the water, onto land earbones evolved from gill arches. 2) think about how évolution works, everything comes from a common ancestor. The common ancestor had five bones in his limbs that will become fingers, but then adding fingers may have become impossible because of wrist composition (it happens, put ain't beneficial or useful). So tetrapods can only "lose" fingerbones.

@@dani.lepore9410 2) It also may be a matter of more than four or five fingers not being biologically cost effective.

@@curiodyssey3867 dink jy Engels is die enigste taal? Not everyone is a native English speaker.

@@emilyjadeoliver Ray Leaf’s last comment was perfectly clear. Pretty sure this one’s just a series of goofs

I’m pulling most of this out of my rear here but, one thing is humans helping each other out, another is myopia increasing with glasses as people survive as well as myopia getting worse as our eyes adjust to constant screen staring not so far away. I wonder I go near sighted people would do close work such as making arrowheads and tools?

Those arent real teeth. Afaik its called horn papillas and used to filtrate water (like some wales do)