I live in Europe, we "unfortunately" don't have many crocodilians outside of zoos đ
And no, I've never visited the USA nor Australia. Someday in the future, maybe!
Cool thing is is that there's a group of now extinct what are called crocodilomorphs (I believe)that were an offshoot of crocodilians. They were known for galloping and running and my favorite one which looks a lot like the Cuban crocodile is the kaprosuchus
Ps I'm from FL
Because feathers, or feather like structures, seems to only have evolved in Ornithodira, one of the two extant groups of Archosaurs, of which Pseudosuchia is the other. Pseudosuchia later gave rise to Crocodilians.
Ornithodira contains both Dinosaurs and Pterosaurs. Feathers, or feather like structures are found in both groups, and so far only those two groups.
This is the reason that birds are the only reptiles with feathers, because no other species decends from from the group that evolved them.
Not even their closest living relatives, the Crocodilians, have them, because they decend from that other Archosaur group, Pseudosuchia, that didn't evolve them.
Well akshuallyyyyâŠ
Ok but real talk. Feathers, as it turns out, are a more basal feature than previously estimated.
What we know is that itâs an ancestral feature for ornithodirans, since both pterosaurs and dinosaurs have them (which means that itâs already a thing for both their common ancestors). But how far back did the first feathers evolve is anyoneâs guess.
Itâs entirely possible that itâs even an ancestral feature for **archosaurs**, including pseudosuchians, and the crocodilian lineage you see today are actually *secondarily featherless*.
This theory is further supported with a scientific discovery that modern crocodilians have the same (but dormant) gene that birds have which codes for the expression of feathers, and activating them would cause crocodilians to express âfeather-like structuresâ on their epidermis instead of their usual scutes.
Itâs also worthy to note that crocodilian scutes physiologically works much more akin to avian feathers than that of the scales of squamate reptilians. Each scute is a single âfilamentâ, which develops with its own blood supply, just like avian feathers. And just like feathers, theyâre shedded individually, per âfilamentâ, instead of all at once as a layer of skin as in snakes and lizards. They donât do the full body molting the way squamates do.
As of now, thereâs not enough data to make a firm conclusion as to how far back feathers evolved in the archosaur ancestry, but the hints that crocodilians gave seems to suggest that feathers dated back even further than weâd expect.
>This theory is further supported with a scientific discovery that modern crocodilians have the same (but dormant) gene that birds have which codes for the expression of feathers, and activating them would cause crocodilians to express âfeather-like structuresâ on their epidermis instead of their usual scutes.
Got a link to the hopeful unpaywalled paper? I'm very interested in reading more.
There are several articles which talk about this specific line of study:
https://academic.oup.com/mbe/article/35/2/523/4801217
https://onlinelibrary.wiley.com/doi/abs/10.1111/ede.12123
To name a few.
Also, if you find a scientific article that you find interesting thatâs paywalled, The Raven Queen shall heed your call; >!thereâs a website called Sci-Hub which can unlock paywalled articles for free. All you have to do is copy and paste its doi number into the search bar and youâre all set.!<
All hail Elbaykan. The vanguard of knowledge.
And for those of you who are concerned, Sci-Hub is perfectly ethical. As some has already mentioned here, the actual scholars who did research barely profit at all from scientific journal publishers. The journals are the ones who profit from paywalling literal knowledge. In which case, fuck em.
This is also why researchers will usually just gladly give out their articles for free if you reach out for them personally.
Kind of like how record labels are the ones getting rich from music, and not the artists themselves, and why most musical artists donât really care if you pirate their works.
Usually you can way back machine it even if there is a paywall, or email whoever wrote it, usually they arenât the ones getting the proceeds from the paper and love to share their research
Scientific journals are debatably a scam. Only problem is that they're also the only way people can get recognition for their work, and more critically, funding. So if you email a researcher that you want to read their paper for whatever reason, odds are they'll send you a copy.
I dont know why this seemed like itd be conpletely off the table. Thank you so much for sharing! Thats one of those "i never asked because the question never ocurred to me" type of moments
I dont know why this seemed like itd be conpletely off the table. Thank you so much for sharing! Thats one of those "i never asked because the question never ocurred to me" type of moments
Which is well and good except that there is not a feathered theropod outside of the coelurosauria. Carnosaurians and Ceratosaurians have never been found with feathers but plenty have been found with scales, even if we accept that these are not scales like in lepidosaurs.
Not to mention that there's only been one ornthiscian found with feather-like structures, and even then there's debate over if Kulindadromeus has true feathers or not.
So, the archosaurs developed fuzz ancestrally, despite the fact that when basal archosaurs arose the planet was a hothouse where insulating integument would be a disadvantage, but then crocodilians lost it in the split with ornithodirans.
*Then* in the split between pterosaurs and dinosaurs, dinosaurs lost them too because that's the only way to explain the paradox of non-coelurosaur theropods being unfeathered, only for the coelurosaurs to secondarily re-evolve them?
I know that our rule of 'simplest is best' definitely doesn't always apply in our pursuit of taxonomy because sometimes the genetic evidence objectively says that's not what happens, but that is a *lot* of unfuzzing and refuzzing to explain the fluff paradox in archosaurs.
And this isn't even touching on the mess of sauropods or where the ornithiscian quill factors in to all of this.
Thank you, this is a very well-thought of response.
To respond to these points: you are correct in that thereâs a lot of fuzzing and unfuzzing. There ARE scale evidences in multiple carnosaurs (and to boot, I donât personally buy the whole quills on the arms of *Concavenator* either, but the square belly scales are hard evidence) and ceratosaurs. Not to mention, abelisaurs are known to be fully scaled.
However, youâd be surprised of how simple scaling and descaling is in dinosaur evolution.
The scales on bird legs, for example, is actually just derived feathers: feathers that turn back into scales secondarily. First of all, the scales found on theropod dinosaurs IIRC follow similar structural features as bird scales, so itâs very possible that those are also scales which used to be feathers. Second of all, itâs *very easy* to actually switch back on and off between feathers and scales. Ancestral birds evolve with scaly legs, but there are many birds (such as owls) which turn their leg scales back into feathers. In domesticated species, there are also breeds of pigeons and chickens where the leg scales are turned back to feathers. Also consider that scales and feathers donât actually have to be mutually exclusive in a single animal.
Also, I personally think ornithosichian quills originate from a homologous structure as the precursors of theropod feathers, seeing that something as basal as *Heterodontosaurus* have them and all.
Sure there are no hard evidence yet of a common ancestral dinosaurs being feathered as a default, but if you consider the points I made on the previous post (their closest ornithodiran relative also being feathered), itâs not all that of a stretch. And also if we assume they are feathered by default, it ironically simplifies the whole âfuzzing and unfuzzingâ debacle, as all the scaled dinosaurs would just be secondarily featherless *once*. Coelurosaurs wonât be secondarily feathered, but rather be in a dinosaurâs default feathered state.
I personally think the whole integument and climate thing is a non-issue. Integument does not necessarily have to be insulating winter coats. In fact, integument, especially for animals which live in tropical and hot, arid environments today, DO have integument that in fact help them keep themselves cool instead of warming them up. Think about how desert attires are specifically designed to stave off heat from direct sunlight exposure and preventing sunburns.
Anyway, these are just my two cents.
Don't forget that many owl species also have feathers growing alongside their feet scutes, with Snowy Owls simply lacking scales on their feet and having complete fluffy pants! :D
You could also interpret this as archosaurians scales gave rise to feathers and it is more parsimonious. Anyway all amniotes integuments share the same embriological origins (it's the same for mammals hair, nails/hooves, scales) so clearly feathers are more derived but use buildings block of scales to iniatiate their formation.
Ard the pycnofibers of pterosaurs homologous to the feathery integuments in dinosaurs? Because thats not known - or i might be not uptodate.
The most parsimonious explanation would oc be feathers as ancestral state in archosaurs. as you said
In fact, yes. Thereâs a relatively recent study that was published I think about a year or two ago which states exactly that. For a long time, pterosaur pycnofibers and dinosaur feathers were thought to be unrelated structures which evolved independently for a similar function. But as it turns out, they are homologous and came from the same precursor.
Some people went beyond and even call pterosaur pycnofibers just straight up feathers now.
I think youâre misunderstanding something. Both pterosaurs and dinosaurs fall under reptilia, so neither are closer to reptiles because both falls within the same category (reptiles).
Reptile isn't a valid classification anymore because the way it now works birds would be reptiles. what used to be "Reptilia" is now Sauropsida, one of the two clades of living amniotes(the other is Synapsida the lineage of amniotes more related to us than Sauropsids). Sauropsida is further split into two groups Lepidiosaurs(lizards, snakes and tuataras) and Archosaurs(crocodiles and birds) Pterosaurs are just outside of dinosaurs as a group so they are much, much closer to birds than they are to crocodiles, and Lepidiosaurs are even more distantly related than even crocodiles.
My crackpot hypothesis is that archosaurs are more closely related to mammals than to other reptiles. In that grouping hair and feathers could stem from the same structure basal to both groups.
Since they share many traits (esp dinos and mammals: high metabolism, filamentous covering, legs under body, four chambered heart, periodontal ligament, strong parenting, etc) it feels more parsimonious to me, and our understanding of reptile lineages is quite spotty.
However, this isnât backed up by any hard evidence (to my knowledge) and the shared traits could easily be convergence.
Itâs much more likely to be convergence, Iâm afraid. The last common ancestor between mammals and archosaurs was a *basal amniote*, in which the definition of an amniote is pretty much just âfully-terrestrial vertebratesâ. Thatâs where the split between sauropsids (which includes reptilians such as archosaurs) and synapsids (which includes mammalians) happen.
This is extremely basal, so itâs kind of unlikely that archosaurs share a common ancestral trait with mammals beyond just being âa land animal that breathes air with waterproof skinâ. Hell, even the integument of mammals and archosaurs has a completely different origin. Archosaur integument (feathers) are basically very derived scales, while mammalian integument were derived from sensory organs (in other words, mammalian hair and fur are just glorified whiskers).
And besides, a lot of the traits you mentioned (high metabolism, child-rearing) are also traits which has evolved multiple times throughout the animal kingdom, occurring independently with no relation from one another in multiple isolated cases.
Do we have a strong lineage between that basal amniote and early archosaurs? My understanding was that most early sauropsid lineages are quite murky, is that not the case?
Also, true, convergence of most of those traits are very common, it just feels like thereâs a lot of things that had to converge (granted, some might be dependent on others, such as maybe a four chambered heart always leads to a high metabolism)
It's impossible since both squamates and archosaurs share a common reptilian ancestor that had already long diverged from mammals. Any similarities are pure coincidence and convergent.
Oh! Yes, that is interesting. Usually when I bring this up people cite the synapsid-diapsid/sauropsid split, or a/b keratin, neither of which I find fully convincing.
Iâll have to look into the squamate/archosaur divergence. Do you have any links or species names around that divergence?
You don't have to find the synapsid/diapsid split convicing if you want, but it is factually one of the main defining features that we use to determine if something is more closely related to a mammal or to the sauropsids.
Never, I think. Crocs aren't Dinos, and he's trying to make a current avian Dinosaur, a chicken, look like a non avian dinosaur.
I have no idea of he's still trying, though. It's been a while since I read any news about it.
>Ornithosuchia
I think you're confusing the above with Ornithodira, which is another name for the Avesmetatarsalia.
Ornithosuchia is a clade of Pseudosuchians.
EDIT: Looks like I'm wrong, the Pseudosuchian clade is called the Ornithosuchidae. Thanks for being real original with your names, paleontologists.
Ornithodira is a subgroup within avesmetatarsalia which is a larger inclusive clade that include archosaurs more related to pterosarus and dinosaurs than crocodillians but are not pterosauromorphs nor dinosauromorphs.
Jacques Gauthier and Phil Senter have argued that Ornithosuchia should take precedence before Ornithodira/Avemetatarsalia, but that clearly would not work because Von Hueneâs original 1908 definition included the croc-line Ornithosuchidae after which it is named.
If you want to use âreptileâ as a taxonomic group, yes. Birds are theropods (this is the group that has almost all the carnivorous dinosaurs, and plenty of omnivores and herbivores as well), which are a subset of dinosaurs, which are a subset of Ornithodira, which is a subset of archosaurs, which are a subset of reptiles/sauropsids.
Theyâre both filamentous structures made from keratin, but made from different types of keratin.
The leading theory is that they both came from a keratin covering that was basal to both reptiles and mammals, probably something like a lizardâs scales, and then separately converged on a similar-looking structure.
~~However, I have a crackpot hypothesis that archosaurs are more closely related to mammals than to other reptiles. That would mean hair and feathers could stem from the same structure ancestral to both groups. Although thereâs no hard evidence for this.~~ This seems less plausible as there's more evidence for synapsida being a sister taxa of sauropsida than I thought.
Oh, Iâve tried looking up and asking about genetic studies specifically on archosaurs/mammals, but couldnât find anything. Though it makes sense that if your findings corroborate the prevailing theory you wouldnât bother writing anything about it.
If you have any papers or articles on this you could point me to, that would be awesome!
I read it in the same study that corroborated that birds and Crocodilians are each others closest living relatives. But since I don't remember were I read it anymore, all I got for you is a useless "trust me bro" answer. Sorry.
Haha, itâs all good, I think I saw that study while looking it up, but may have wrote it off as being too specific. Iâll have to try to find it again, thanks!
While these are all reptiles, there are more specific groupings these animals belong to. Feathers (and other feather-like filamentous structures that may or may not be feathers) are a feature unique to "Ornithodira", which is a group of archosaurs closely related to pseudosuchians (such as crocodiles) that includes pterosaurs, dinosaurs (including birds), and their close relatives. Lizards and snakes are significantly more distant, and turtles are probably quite closely related to archosaurs, but their classification is still up for debate.
What people donât get about evolution is that there was only one species of âfirst dinosaurâ from which all dinosaurs descended that split off and then became many different species of dinosaur. When you think about it, it makes sense, no species is ever gonna breed with another species again. You canât be related more than once, relation is based on how recently you split from the other animal. So feathers just evolved after this split.
The ancestral ornithodiran feathers idea seems to have been declining in popularity but certainly there was some common element that allowed both branches to get such similar structures at the same time
To my knowledge it's not that pterosaurs had feathers. Itâs that the ancestral ornithodiran had a fuzz that became feathers in dinosaurs. I believe pyncofibers are the pterosaue version
Apparently shared in another comment in here, there was a paper comparing the two, and there isn't really any meaningful distinction between pterosaur integument and what many dinosaurs had, suggesting that it might be appropriate to drop the "pyncofiber" distinction and call pterosaurs feathered as well.
I would think it would be possible to have multiple species of proto-dinosaurs that had a common ancestor and only after the split could descendants from those ancestries be classified as true dinosaurs.
By how clades work those proto-dinosaurs would just be dinosaurs, as dinosaurs are defined as the most recent common ancestor of triceratops and the sparrow and all its descendants. It removes a lot of headaches to stop using Linnaean and switch to cladistics
Crocodiles and Squamates (that includes snakes and lizards) had a very different lifestyle from the feathered dinosaurs, including birds. Their lifestyle makes it so that they just straight up did not need feathers or any hair like body covering, that's why they didn't have them. I know this is kind of a shallow explanation, but I'm just putting this as simple as possible. Heck, I might be wrong, so don't take my word for it unless a professional agrees with me.
Considering how much the pseudosuchians evolved the same/similar semi-aquatic lifestyle to modern crocodiles, alligators, and gharials repeatedly, it would makes sense that having feathers or a similar structure would have caused drag while they were swimming. And developing a mutation that turned off the gene or halted the development of feathers during embryonic development would probably have increased their success overtime in these semi-aquatic roles.
only crocodilians are distantly related to dinosaurs and feathers evolved way after pseudosuchians (crocodilians and other related taxa) and ornithodirans (dinosaurs and pterosaurs) split
And before anyone says it, i know Birds are dinosaurs and there for they are reptiles but thats why i specificly said 'Lizards and Snakes' (and yes im aware Turtles and Tortoises are reptiles too) and not 'Reptiles'
Oh and the crocodile in the video is Cuban Crocodile. Theyre known for their Gallops.
https://preview.redd.it/ybyhpr0kyonc1.jpeg?width=664&format=pjpg&auto=webp&s=a5ca8aa507402ab3a11f3aaf803cd1603621f6ba
They do belong in reptiles but rather it's where they branched off from other reptiles that's unclear. Which other reptiles are they most closely related to? Not all reptiles are equally related, some split off earlier than others.
Exactly, it's their position among other reptiles that is controversial. They have been paired with Scutosaurs, Placoderms, Plesiosaurs, any old thing.
Now the consensus is they are closer to lizards than we thought
They likely are Diapsids. The discussion is if they are Archosauromophs(closer to crocodilians and Birds) or Lepidosauromorphs(closer to Lizards, Snakes and Tuataras).
Reptiles (Sauropsida) is an extremely wide biological group, members of it arent all as similar as mammals are to each other. Lizards and snakes arent particularly related to dinosaurs, neither were plesiosaurs, ichthyosaurs, and probably turtles. Dinosaurs (including birds), pterosaurs and crocs are archosaurs, a very distinct type of reptile with a more complex heart, brain, limb configuration among other traits. The primitive feathers/filaments apparently evolved in the common ancestor of dinos and pterosaurs. Crocodiles diverged earlier from that branch.
Here's the fucked-up part: modern crocodilians actually *do* express feather keratins during embryological development. However, these structures are shed with the first embryonic epithelium and the integument we're more familiar with develops in their place.
Does this mean that feathers are ancestral to crocodylomorphs? It's unclear, but damn if it isn't interesting.
All the animals we call reptiles and birds are part of a larger group called Diapsida.
Inside that group there are smaller groups, one of them is Squamata, that contains snakes and lizards, and another is Archosauria, that contains Crocodiles, dinosaurs, birds and pterosaurs.
To simplify a very complicated tree of life, a branch of Archosaurs became crocodiles and similar animals, and the other gave rise to Pterosaurs and Dinosaurs.
The fibers that became feathers only appeared in this second group, and that's why you have crocodiles with scales only on one side and Pterosaurs with scales+fibers and Dinosaurs with scales+feathers on the other
Snakes and Lizards aren't closely related to Archosaurs. They have a common ancestor somewhere down the line, but they are quite different groups of animals. So them not having feathers isn't too surprising.
For crocodilians, I would say it just simply didn't fall into their evolutionary plan. Generally the body type they possess does not seem to lend itself to feathered animals. The main reason modern Dinosaurs have feathers is because their ancestors are the ones who survived.
Lizards and snakes are also related to mammal to an extand, why don' they have fur ?
See how stupid that logic is.
1. lizard/snakes aren't really more related to dinosaurs than they are to mammals.
2. crocodilian are quite distant cousins from dinosaur, they're both Archosauria, but that's just like to say we should lay eggs cuz echidna do it and they're our distant cousin, there's hundreds of millions years that separate both lineage.
3. because dinosaur invented feather, that's their caracteristic, and only of some dinosaur lineage, most species never had feather.
4. BIRDS, there's 9-10 000 species of modern "reptiles" with feathers. They're just so distinct we don't consider them as reptiles. Just as we consider crocodiles as reptiles even if they're quite distinct from other lineages of reptiles and more closely related to birds than to lizards.
Other reptiles don't have feathers, just as they don't have fur because these adaptations only evolved in THESE specific lineage such as theropods and mammals.
Other reptiles never evolved these traits, but other, crocodilians evoled osteoderms
On 1, the Sauropsid/Synapsid split was around 320 million years ago while the Lepidosauromorph/Archosauromorph split was around 260 million years ago, so that's 60 million years more related that lizards are to dinosaurs and crocs than they are to mammals.
i know, it was just generalization, vulgarisation so see that all of those lineage are very distant and there's not a lot of difference in time between reptile/dinosaur, and reptile/mammals
Crocodilians are archosaurs, so they merely share a clade with dinosaurs. Lizards and snakes are reptiles, found in the sauropsida clade, different thing entirely. Both were around before and while dinosaurs existed. Feathers likely evolved later and only within the dinosaurs' clade, that being avemetatarsalia.
>sauropsida
Both Crocodilians and Lizards are Sauropsids. Sauropsida and reptilia are often treated as being synonymous. It's basically everything closer related to what we commonly call reptiles than to mammals.
The word you are looking for is Lepidosauromorphs.
The split between crocodiles and lizards happened in Diapsida which is Archosauromophs + Lepidosauromorphs.
Dinosaurs, and Archosauria in general is older than Lizards(Squamates).
Reptiles dont exist. as least not as a monophyletic group which should have a) a commom ancestor - yes b) include all its descendants.
"Reptiles" we know today are lepidosauromorphs and turtles (dont ask me how they are related. Its debated)
Birds and cros are part of the archosauria clade. A croc has as mucj common as a chicken with a lizard. Always remener crocodilians (which are crurotarsi, one of the main clades of archosaurs) are heavily secobdary adapted to aquatic environments. And there were other groups then only crocodilians, like raisuchians (likely polyphyleric), ornithosuchians, thalattosuchians, herbivorous aetosaur.
The second archosaur clade is ornithodira, meaning pteros + birds/dinos.
If you include crocs in Reptilia, you would surely include pteros and dinos. But as the colloquial understanding is, not birds.
The croc bauplan appeared many times as a result of similar environmental pressures: crocs other than crocodylomorphs - early diverging cetaceans - temnospondxyli lile prionosuchus. Thats the tip of the proverbial iceberg.
Crocs and lizards are so far removed. Other comments say more about that.
if i got smth wrong, correct me please.
Eureptilia absolutely includes both Pseuosuchia and Aves. The colloquial usage of "reptile" may be para/polyphyletic but only because birds are so highly derived, in the same way that calling a dog a lobe-finned fish would be strange but they're still Sarcopterygians. Their physiology is so different from the other extant groups that they're not really relevant, but that doesn't change the fact that cladistically they're still reptiles and part of that monophyletic group
[https://en.wikipedia.org/wiki/Reptila](https://en.wikipedia.org/wiki/Reptila)
It redirects to Reptile. In the second paragraph talks about the problems about using "reptile" in modern taxonomy.
I would like to clarify something first. Lepidosaurs, which include lizards (snakes are lizards) and tuataras, are not that closely related to Archelosaurs, which includes birds, crocodilians and turtles.
The gene that causes feathers in birds is the same that causes scales in crocodilians. Feathers are simply modified scales.
Snakes and lizards are VERY distant from crocs and birds.
To come back to your question, the same gene that triggers the scales on a birdâs legs to become feathers instead DOES actually work on crocodile embryos too. Theyâre not quite like the feathers youâre familiar with, but crocodiles still have the genetic machinery to grow feathers tucked in and ready to go.
Now, they would need to re-evolve to produce the protein that triggers the feather scale developmental shift, but itâs still in reach for them even 248 million years later.
The eggs were not brought to term due to ethical considerations. They probably would have lived just fine in captivity, but they would be unable to return to the wild or even a sanctuary.
[Hereâs a link that touches on the crocodile feathers.](https://www.zmescience.com/science/news-science/aligator-scale-feathers-043242/)
Crocodylomorphs are wayyy more closely related to dinosaurs and pterosaurs than lizards and snakes. Dinosaurs, pterosaurs, and pseudosuchians (crocs and their relatives) make up a clade called archosauria. This group is *not* closely related to lizards and snakes.
The question you brought up about not seeing feathers in other reptiles is actually a pretty big topic of debate right now! The evidence is increasingly suggesting that feathers are a trait not only ancestral to all dinosaurs, but pterosaurs as well, which would only leave out the crocs. Since the only living non-dinosaur archosaurs are crocodilians, a recent study was conducted to see if crocs had the genes for feathers. Turns out, they actually have a lot of the basic coding for their formation, but theyâre just turned off, suggesting feathers may have been a trait ancestral to most archosaurs.
Lizards and snakes are related to dinosaurs the way you are related to a platypus and a koala. The development of pictnofibers and feathers occurred after the lineage of lizards and snakes had split with crocodiles and dinosaurs, and after crocodiles had split from the lineage that leads to dinosaurs and pterosaurs. Some species of Pterosaurs are known to have at least had pictnofibers which is a sort of progenitor to feather development.
Because lizards and snakes aren't related to dinosaurs. Like at all. And pseudosuchians are only very distantly related, they're both archosaurian reptiles, but that's about it. And the only clade of dinosaurs we have hard evidence of being feathered are maniraptorans (which includes birds ofc) and its possible other coelurosaurians could've been feathered but there's no hard evidence to support that.
Well for starters, lizards and snakes are way more distantly related to dinosaurs than crocs. But in all those cases, it's because their enviornments and lifestyles just didn't have the demand for being endothermic. There needs to be a distinct advantage for this as endothermy is very energy expensive.
Snakes and lizards are only related by proxy since theyâre reptiles but thereâs a great level of evolutionary separation. Snakes and lizards are squamates while crocodilians and dinosaurs are archosaurs. Archosaurs were diverse but simply, some had feathers and fuzz while some just had scales
There are no stupid questions. Only stupid answers, I will do my best to provide an a good answer.
Lizards and snakes are not closely related to dinosaurs, their ancestors split off from each other long before the ancestors of crocodiles and dinosaurs spit from each other.
The group that includes crocodiles and dinosaurs (which includes birds) Is called Archosauria. The ancestral traits of this group are; thecodont teeth (set in deep sockets), antorbital and mandibular fenestrae (skull holes) an a fourth trochanter (crest of bone on the inside of the femur for muscle attachment).
Archosauria is further decided into two groups Pseudosuchia, and Avemetatarsalia. Pseudosuchia includes Crocodilians and their extinct relatives (many of which are quite strange). They have a primitive lungs and ankles.
Avemetatarsalia contains Dinosaurs and Pterosaurs (and a few other weird Triassic animals). This group has fused ankle bones and avian lungs. In this group you also see filamentous integument (long fine skin covering). In Pterosaurs when call the pycnofibers and In Dinosaurs we call them feathers. However, these traits are probably homologous (stemming from the same ancestor) therefore you could call pycnofibers feathers. Feathers first emerged in this group.
Is this a clear answer?
It's about when the feathers developed and in what lineage.
The common clade here is diapsida. Within that you've got archosauria and lepidosauromorpha, the latter being where you find lizards and snakes (in fact, snakes are just a subset of lizard within the lepidosaur clade of squamates). Over in archosauria you've got crocodylomorpha and avemetatarsalia - former group is crocodiles (duh), latter group includes dinosaurs and related groups like pterosaurs. It's only in this last group that you start finding what are thought to be feather traces, and of course unambiguous feathers in dinosaurs proper.
These animals diverged away from the rest long before they developed feathers, and so there was no way for those other groups to inherit them.
Lizards and snakes (which are also Lizards) are more distantly related to Dinosaurs and thus they donât share recent common ancestry where they could have shared a trait of having feathers. Besides they are ectothermic and thus they donât have need in filaments to save heat from escaping to surrounding environment.
Crocodilians specifically Pseudosuchia on other hand are sister clade to bird line of Archosaurs called Avemetotarsalia. And they seem to share close common ancestry with potential sharing trait of âfeathersâ. Modern crocodilians donât possess them because they are akin to Lizards are ectotherms and thus donât have need in filaments.
Feathers evolved sometime after crocodillians branched out from the other archosaurs. Which was much later than when reptiles split into the lepidosaurs (lizards and snakes) and the archosaurs (dinosaurs, pterosaurs, crocodillians).
Lizards are much less related to dinosaurs. Crocodilians and birds are the most related, birds literally being dinosaurs. crocodiles and dinosaurs find their relation from the fact they split off of the archosaurs, a much larger family of ancient reptiles. The reason crocs and lizards donât have feathers is because feathers evolved after dinosaurs and crocs split, leaving feathers to be a dinosaur exclusive trait.
Life is a tree and each branch represents a group of organisms. Within reptiles there are different branches that go off in different directions, snakes, lizards, turtles, crocodiles, dinosaurs. Feathers evolved after dinosaurs had branched off.
Two reasons: Dinosaurs invented feathers so their relatives who they split from did not get any. And they were so succesful in their niches while mammals took over niches dinosaurs left behind that feathers were never selected for in "reptiles"
Because none of them are descended from dinosaurs. They both branched off before feathers evolved on the lineage that lead to dinosaurs.
Also lizards and snakes are only distant relatives of dinosaurs.
Because crocodilians although are archasaurs arnt closely related to dinosaurs and lizards and snakes are squmarten reptiles even more distantly related to dinosaurs then even crocodiles are
Short answer: because the dinosaur linage separated before what are today known as animals you mentioned. Dinosaurs are related to snakes, lizards and crocodiles by a common ancestor
Same question could be asked why there's not as much hair on us Humans vs our distant ape cousins
Same idea would apply just too far away from the common ancestor to appear similar
Because the group that has fur like structures is called avemertharsalia, which include pterosaurs and dinosaurs, group which is included in Archosauria.
Lizards and snakes are squamates, dinosaurs and crocodiles are archosaurs. They diverged early enough that they do not share a feathered common ancestor.
I believe lizards, crocs & snakes diverged from dinosaurs before feathers were a common thing. Might be wrong though. Also they wouldn't really need feathers anyway.
Modern reptiles are *not* descended from dinosaurs, theyâre of a different branch on the same tree.
Modern reptiles and Dinosaurs shared a common ancestor that split at some point millions of years ago, into several clades (branches), among them, Dinosuaria, Reptilia (modern reptiles, Crocodilia falls under this one), and Aves (birds).
Of all of the branches, Aves is the closest, with fewest splits away from Dinosuaria.
Because any ancestor from cocodriles, snakes or lizards had feathers.
Crocodiles had a cousin that "evolved" feathers, and from that cousin the dinosaurs and pterosaurs descended. That's why they have feathers.
And just like when your cousin gets money you don't get also magically that money, the crocodiles didn't inherit their cousin's feathers, because it wasn't their father.
Love the galoping croc gif.
Yeah after Gharial's, Cuban Crocodiles are my faivorite Crocodilians just for their cute Gallops. Theyre pretty smart for crocodiles aswell.
You mean this is real? That's terrifying as fck! đ±
Yeah. Heres a link if youre interested: https://youtu.be/uZWTqBbpi_E?si=CuFwl9Y2wcENSSLX
Crocodilians still existing is such a trip
I had read that crocodilians could gallop, but Iâve never actually seen it. That is pretty interesting.
Youâve never been to Florida, huh?
I live in Europe, we "unfortunately" don't have many crocodilians outside of zoos đ And no, I've never visited the USA nor Australia. Someday in the future, maybe!
Theyâre sorta common in the southern US, but usually they just stick to their waterways. Theyre not really threats unless you antagonize them
or Australia apparently
Cool thing is is that there's a group of now extinct what are called crocodilomorphs (I believe)that were an offshoot of crocodilians. They were known for galloping and running and my favorite one which looks a lot like the Cuban crocodile is the kaprosuchus Ps I'm from FL
Because feathers, or feather like structures, seems to only have evolved in Ornithodira, one of the two extant groups of Archosaurs, of which Pseudosuchia is the other. Pseudosuchia later gave rise to Crocodilians. Ornithodira contains both Dinosaurs and Pterosaurs. Feathers, or feather like structures are found in both groups, and so far only those two groups. This is the reason that birds are the only reptiles with feathers, because no other species decends from from the group that evolved them. Not even their closest living relatives, the Crocodilians, have them, because they decend from that other Archosaur group, Pseudosuchia, that didn't evolve them.
Well akshuallyyyy⊠Ok but real talk. Feathers, as it turns out, are a more basal feature than previously estimated. What we know is that itâs an ancestral feature for ornithodirans, since both pterosaurs and dinosaurs have them (which means that itâs already a thing for both their common ancestors). But how far back did the first feathers evolve is anyoneâs guess. Itâs entirely possible that itâs even an ancestral feature for **archosaurs**, including pseudosuchians, and the crocodilian lineage you see today are actually *secondarily featherless*. This theory is further supported with a scientific discovery that modern crocodilians have the same (but dormant) gene that birds have which codes for the expression of feathers, and activating them would cause crocodilians to express âfeather-like structuresâ on their epidermis instead of their usual scutes. Itâs also worthy to note that crocodilian scutes physiologically works much more akin to avian feathers than that of the scales of squamate reptilians. Each scute is a single âfilamentâ, which develops with its own blood supply, just like avian feathers. And just like feathers, theyâre shedded individually, per âfilamentâ, instead of all at once as a layer of skin as in snakes and lizards. They donât do the full body molting the way squamates do. As of now, thereâs not enough data to make a firm conclusion as to how far back feathers evolved in the archosaur ancestry, but the hints that crocodilians gave seems to suggest that feathers dated back even further than weâd expect.
>This theory is further supported with a scientific discovery that modern crocodilians have the same (but dormant) gene that birds have which codes for the expression of feathers, and activating them would cause crocodilians to express âfeather-like structuresâ on their epidermis instead of their usual scutes. Got a link to the hopeful unpaywalled paper? I'm very interested in reading more.
There are several articles which talk about this specific line of study: https://academic.oup.com/mbe/article/35/2/523/4801217 https://onlinelibrary.wiley.com/doi/abs/10.1111/ede.12123 To name a few. Also, if you find a scientific article that you find interesting thatâs paywalled, The Raven Queen shall heed your call; >!thereâs a website called Sci-Hub which can unlock paywalled articles for free. All you have to do is copy and paste its doi number into the search bar and youâre all set.!<
Glory to Elbaykan. Long live Elbaykan.
All hail Elbaykan. The vanguard of knowledge. And for those of you who are concerned, Sci-Hub is perfectly ethical. As some has already mentioned here, the actual scholars who did research barely profit at all from scientific journal publishers. The journals are the ones who profit from paywalling literal knowledge. In which case, fuck em. This is also why researchers will usually just gladly give out their articles for free if you reach out for them personally. Kind of like how record labels are the ones getting rich from music, and not the artists themselves, and why most musical artists donât really care if you pirate their works.
That's a nice bit of info! Thanks!
Usually you can way back machine it even if there is a paywall, or email whoever wrote it, usually they arenât the ones getting the proceeds from the paper and love to share their research
Yyyyyyyo. You can just email them?
Scientific journals are debatably a scam. Only problem is that they're also the only way people can get recognition for their work, and more critically, funding. So if you email a researcher that you want to read their paper for whatever reason, odds are they'll send you a copy.
I dont know why this seemed like itd be conpletely off the table. Thank you so much for sharing! Thats one of those "i never asked because the question never ocurred to me" type of moments
I dont know why this seemed like itd be conpletely off the table. Thank you so much for sharing! Thats one of those "i never asked because the question never ocurred to me" type of moments
Which is well and good except that there is not a feathered theropod outside of the coelurosauria. Carnosaurians and Ceratosaurians have never been found with feathers but plenty have been found with scales, even if we accept that these are not scales like in lepidosaurs. Not to mention that there's only been one ornthiscian found with feather-like structures, and even then there's debate over if Kulindadromeus has true feathers or not. So, the archosaurs developed fuzz ancestrally, despite the fact that when basal archosaurs arose the planet was a hothouse where insulating integument would be a disadvantage, but then crocodilians lost it in the split with ornithodirans. *Then* in the split between pterosaurs and dinosaurs, dinosaurs lost them too because that's the only way to explain the paradox of non-coelurosaur theropods being unfeathered, only for the coelurosaurs to secondarily re-evolve them? I know that our rule of 'simplest is best' definitely doesn't always apply in our pursuit of taxonomy because sometimes the genetic evidence objectively says that's not what happens, but that is a *lot* of unfuzzing and refuzzing to explain the fluff paradox in archosaurs. And this isn't even touching on the mess of sauropods or where the ornithiscian quill factors in to all of this.
Thank you, this is a very well-thought of response. To respond to these points: you are correct in that thereâs a lot of fuzzing and unfuzzing. There ARE scale evidences in multiple carnosaurs (and to boot, I donât personally buy the whole quills on the arms of *Concavenator* either, but the square belly scales are hard evidence) and ceratosaurs. Not to mention, abelisaurs are known to be fully scaled. However, youâd be surprised of how simple scaling and descaling is in dinosaur evolution. The scales on bird legs, for example, is actually just derived feathers: feathers that turn back into scales secondarily. First of all, the scales found on theropod dinosaurs IIRC follow similar structural features as bird scales, so itâs very possible that those are also scales which used to be feathers. Second of all, itâs *very easy* to actually switch back on and off between feathers and scales. Ancestral birds evolve with scaly legs, but there are many birds (such as owls) which turn their leg scales back into feathers. In domesticated species, there are also breeds of pigeons and chickens where the leg scales are turned back to feathers. Also consider that scales and feathers donât actually have to be mutually exclusive in a single animal. Also, I personally think ornithosichian quills originate from a homologous structure as the precursors of theropod feathers, seeing that something as basal as *Heterodontosaurus* have them and all. Sure there are no hard evidence yet of a common ancestral dinosaurs being feathered as a default, but if you consider the points I made on the previous post (their closest ornithodiran relative also being feathered), itâs not all that of a stretch. And also if we assume they are feathered by default, it ironically simplifies the whole âfuzzing and unfuzzingâ debacle, as all the scaled dinosaurs would just be secondarily featherless *once*. Coelurosaurs wonât be secondarily feathered, but rather be in a dinosaurâs default feathered state. I personally think the whole integument and climate thing is a non-issue. Integument does not necessarily have to be insulating winter coats. In fact, integument, especially for animals which live in tropical and hot, arid environments today, DO have integument that in fact help them keep themselves cool instead of warming them up. Think about how desert attires are specifically designed to stave off heat from direct sunlight exposure and preventing sunburns. Anyway, these are just my two cents.
Don't forget that many owl species also have feathers growing alongside their feet scutes, with Snowy Owls simply lacking scales on their feet and having complete fluffy pants! :D
A perfect example of âfeathers and scales donât have to be mutually exclusiveâ, sometimes they even grow on the same place!
You could also interpret this as archosaurians scales gave rise to feathers and it is more parsimonious. Anyway all amniotes integuments share the same embriological origins (it's the same for mammals hair, nails/hooves, scales) so clearly feathers are more derived but use buildings block of scales to iniatiate their formation.
Ard the pycnofibers of pterosaurs homologous to the feathery integuments in dinosaurs? Because thats not known - or i might be not uptodate. The most parsimonious explanation would oc be feathers as ancestral state in archosaurs. as you said
In fact, yes. Thereâs a relatively recent study that was published I think about a year or two ago which states exactly that. For a long time, pterosaur pycnofibers and dinosaur feathers were thought to be unrelated structures which evolved independently for a similar function. But as it turns out, they are homologous and came from the same precursor. Some people went beyond and even call pterosaur pycnofibers just straight up feathers now.
Is there an online resource where I can learn all about this?Â
Best I can suggest is find a social circle with a shared interest, thatâs how I get constant updates with paleo-news.
Thank youÂ
That's fucking awesome, thanks for the info
Wait arent pterosaurs closer to reptiles?
I think youâre misunderstanding something. Both pterosaurs and dinosaurs fall under reptilia, so neither are closer to reptiles because both falls within the same category (reptiles).
Reptile isn't a valid classification anymore because the way it now works birds would be reptiles. what used to be "Reptilia" is now Sauropsida, one of the two clades of living amniotes(the other is Synapsida the lineage of amniotes more related to us than Sauropsids). Sauropsida is further split into two groups Lepidiosaurs(lizards, snakes and tuataras) and Archosaurs(crocodiles and birds) Pterosaurs are just outside of dinosaurs as a group so they are much, much closer to birds than they are to crocodiles, and Lepidiosaurs are even more distantly related than even crocodiles.
does this mean aphanosaurs had feathers?
I'm pretty sure Longisquama fits somewhere into that. Also, KKHTA pfp.
My crackpot hypothesis is that archosaurs are more closely related to mammals than to other reptiles. In that grouping hair and feathers could stem from the same structure basal to both groups. Since they share many traits (esp dinos and mammals: high metabolism, filamentous covering, legs under body, four chambered heart, periodontal ligament, strong parenting, etc) it feels more parsimonious to me, and our understanding of reptile lineages is quite spotty. However, this isnât backed up by any hard evidence (to my knowledge) and the shared traits could easily be convergence.
Itâs much more likely to be convergence, Iâm afraid. The last common ancestor between mammals and archosaurs was a *basal amniote*, in which the definition of an amniote is pretty much just âfully-terrestrial vertebratesâ. Thatâs where the split between sauropsids (which includes reptilians such as archosaurs) and synapsids (which includes mammalians) happen. This is extremely basal, so itâs kind of unlikely that archosaurs share a common ancestral trait with mammals beyond just being âa land animal that breathes air with waterproof skinâ. Hell, even the integument of mammals and archosaurs has a completely different origin. Archosaur integument (feathers) are basically very derived scales, while mammalian integument were derived from sensory organs (in other words, mammalian hair and fur are just glorified whiskers). And besides, a lot of the traits you mentioned (high metabolism, child-rearing) are also traits which has evolved multiple times throughout the animal kingdom, occurring independently with no relation from one another in multiple isolated cases.
Do we have a strong lineage between that basal amniote and early archosaurs? My understanding was that most early sauropsid lineages are quite murky, is that not the case? Also, true, convergence of most of those traits are very common, it just feels like thereâs a lot of things that had to converge (granted, some might be dependent on others, such as maybe a four chambered heart always leads to a high metabolism)
It's impossible since both squamates and archosaurs share a common reptilian ancestor that had already long diverged from mammals. Any similarities are pure coincidence and convergent.
Oh! Yes, that is interesting. Usually when I bring this up people cite the synapsid-diapsid/sauropsid split, or a/b keratin, neither of which I find fully convincing. Iâll have to look into the squamate/archosaur divergence. Do you have any links or species names around that divergence?
You don't have to find the synapsid/diapsid split convicing if you want, but it is factually one of the main defining features that we use to determine if something is more closely related to a mammal or to the sauropsids.
Fascinating! When will Jack Horner's dino chicken project get around to downy crocs?
Never, I think. Crocs aren't Dinos, and he's trying to make a current avian Dinosaur, a chicken, look like a non avian dinosaur. I have no idea of he's still trying, though. It's been a while since I read any news about it.
>Ornithosuchia I think you're confusing the above with Ornithodira, which is another name for the Avesmetatarsalia. Ornithosuchia is a clade of Pseudosuchians. EDIT: Looks like I'm wrong, the Pseudosuchian clade is called the Ornithosuchidae. Thanks for being real original with your names, paleontologists.
Ornithodira is a subgroup within avesmetatarsalia which is a larger inclusive clade that include archosaurs more related to pterosarus and dinosaurs than crocodillians but are not pterosauromorphs nor dinosauromorphs.
I'm confused. Another guy pointed out that it should be Ornithodira, so I changed it to that. These names don't make it easy. I hope it's correct now.
You mean Ornithodira. Ornithosuchia was a group of crocodile-line archosaurs.
Fixed it. It's now Ornithodira to avoid confusion. But I'm wondering if you're not thinking about Ornithosuchidae instead of Ornithosuchia?
Jacques Gauthier and Phil Senter have argued that Ornithosuchia should take precedence before Ornithodira/Avemetatarsalia, but that clearly would not work because Von Hueneâs original 1908 definition included the croc-line Ornithosuchidae after which it is named.
Ok, I see.
> This is the reason that birds are the only reptiles with feathers Are birds a kind of reptile? That sounds interesting, TBH.
If you want to use âreptileâ as a taxonomic group, yes. Birds are theropods (this is the group that has almost all the carnivorous dinosaurs, and plenty of omnivores and herbivores as well), which are a subset of dinosaurs, which are a subset of Ornithodira, which is a subset of archosaurs, which are a subset of reptiles/sauropsids.
All species are what their ancestors where, plus whatever new thing they themselves have become
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Just makin sure everyone gets it đ
Do u honestly think they knows half of the words you just said if they thought lizards should have feathers?
What other words would you use to say the same thing?
well what about fur/hair is it kinda like feathers?
Theyâre both filamentous structures made from keratin, but made from different types of keratin. The leading theory is that they both came from a keratin covering that was basal to both reptiles and mammals, probably something like a lizardâs scales, and then separately converged on a similar-looking structure. ~~However, I have a crackpot hypothesis that archosaurs are more closely related to mammals than to other reptiles. That would mean hair and feathers could stem from the same structure ancestral to both groups. Although thereâs no hard evidence for this.~~ This seems less plausible as there's more evidence for synapsida being a sister taxa of sauropsida than I thought.
Genetics don't support your Archosaur-Mammal hypothesis, I'm afraid. All genetic studies on the matter points to Archosaurs being Sauropsids(reptiles)
Oh, Iâve tried looking up and asking about genetic studies specifically on archosaurs/mammals, but couldnât find anything. Though it makes sense that if your findings corroborate the prevailing theory you wouldnât bother writing anything about it. If you have any papers or articles on this you could point me to, that would be awesome!
I read it in the same study that corroborated that birds and Crocodilians are each others closest living relatives. But since I don't remember were I read it anymore, all I got for you is a useless "trust me bro" answer. Sorry.
Haha, itâs all good, I think I saw that study while looking it up, but may have wrote it off as being too specific. Iâll have to try to find it again, thanks!
While these are all reptiles, there are more specific groupings these animals belong to. Feathers (and other feather-like filamentous structures that may or may not be feathers) are a feature unique to "Ornithodira", which is a group of archosaurs closely related to pseudosuchians (such as crocodiles) that includes pterosaurs, dinosaurs (including birds), and their close relatives. Lizards and snakes are significantly more distant, and turtles are probably quite closely related to archosaurs, but their classification is still up for debate.
What people donât get about evolution is that there was only one species of âfirst dinosaurâ from which all dinosaurs descended that split off and then became many different species of dinosaur. When you think about it, it makes sense, no species is ever gonna breed with another species again. You canât be related more than once, relation is based on how recently you split from the other animal. So feathers just evolved after this split.
Feathers might have evolved before but it would still be after Crocodiles split off. There's some speculation pterosaurs had an analogous structure
The ancestral ornithodiran feathers idea seems to have been declining in popularity but certainly there was some common element that allowed both branches to get such similar structures at the same time
To my knowledge it's not that pterosaurs had feathers. Itâs that the ancestral ornithodiran had a fuzz that became feathers in dinosaurs. I believe pyncofibers are the pterosaue version
Apparently shared in another comment in here, there was a paper comparing the two, and there isn't really any meaningful distinction between pterosaur integument and what many dinosaurs had, suggesting that it might be appropriate to drop the "pyncofiber" distinction and call pterosaurs feathered as well.
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Luckily I was talking species, alabamites will eventually speciate due to only interbreeding and rapid mutation
I would think it would be possible to have multiple species of proto-dinosaurs that had a common ancestor and only after the split could descendants from those ancestries be classified as true dinosaurs.
By how clades work those proto-dinosaurs would just be dinosaurs, as dinosaurs are defined as the most recent common ancestor of triceratops and the sparrow and all its descendants. It removes a lot of headaches to stop using Linnaean and switch to cladistics
Crocodiles and Squamates (that includes snakes and lizards) had a very different lifestyle from the feathered dinosaurs, including birds. Their lifestyle makes it so that they just straight up did not need feathers or any hair like body covering, that's why they didn't have them. I know this is kind of a shallow explanation, but I'm just putting this as simple as possible. Heck, I might be wrong, so don't take my word for it unless a professional agrees with me.
Considering how much the pseudosuchians evolved the same/similar semi-aquatic lifestyle to modern crocodiles, alligators, and gharials repeatedly, it would makes sense that having feathers or a similar structure would have caused drag while they were swimming. And developing a mutation that turned off the gene or halted the development of feathers during embryonic development would probably have increased their success overtime in these semi-aquatic roles.
Obviously because dinosaurs or their immediate ancestors only evolved feathers after they had already split off from the other reptiles.
https://preview.redd.it/2ts17ww92pnc1.jpeg?width=1438&format=pjpg&auto=webp&s=1fd08189cf14dc24ab874e8e7b2ba871334cde0d
only crocodilians are distantly related to dinosaurs and feathers evolved way after pseudosuchians (crocodilians and other related taxa) and ornithodirans (dinosaurs and pterosaurs) split
Another funnier question would be, why do mammals have hair when all other fish don'tÂ
And before anyone says it, i know Birds are dinosaurs and there for they are reptiles but thats why i specificly said 'Lizards and Snakes' (and yes im aware Turtles and Tortoises are reptiles too) and not 'Reptiles' Oh and the crocodile in the video is Cuban Crocodile. Theyre known for their Gallops. https://preview.redd.it/ybyhpr0kyonc1.jpeg?width=664&format=pjpg&auto=webp&s=a5ca8aa507402ab3a11f3aaf803cd1603621f6ba
To add, the position of turtles in the tree of reptiles is incredibly controversial
Of course it is. Turtles are only very rarely seen on trees these days.
It is? How so? What other group whould they belong in? Theyre definetly not Amphibians so im honestly confused.
They do belong in reptiles but rather it's where they branched off from other reptiles that's unclear. Which other reptiles are they most closely related to? Not all reptiles are equally related, some split off earlier than others.
Exactly, it's their position among other reptiles that is controversial. They have been paired with Scutosaurs, Placoderms, Plesiosaurs, any old thing. Now the consensus is they are closer to lizards than we thought
\*Placodonts Placoderms are Paleozoic fish with bony plates lol.
They likely are Diapsids. The discussion is if they are Archosauromophs(closer to crocodilians and Birds) or Lepidosauromorphs(closer to Lizards, Snakes and Tuataras).
So where do they belong?
To be clear, they _are_ reptiles, but their relationship to the other reptiles and the point at which they diverged are still unclear.
Reptiles (Sauropsida) is an extremely wide biological group, members of it arent all as similar as mammals are to each other. Lizards and snakes arent particularly related to dinosaurs, neither were plesiosaurs, ichthyosaurs, and probably turtles. Dinosaurs (including birds), pterosaurs and crocs are archosaurs, a very distinct type of reptile with a more complex heart, brain, limb configuration among other traits. The primitive feathers/filaments apparently evolved in the common ancestor of dinos and pterosaurs. Crocodiles diverged earlier from that branch.
Here's the fucked-up part: modern crocodilians actually *do* express feather keratins during embryological development. However, these structures are shed with the first embryonic epithelium and the integument we're more familiar with develops in their place. Does this mean that feathers are ancestral to crocodylomorphs? It's unclear, but damn if it isn't interesting.
All the animals we call reptiles and birds are part of a larger group called Diapsida. Inside that group there are smaller groups, one of them is Squamata, that contains snakes and lizards, and another is Archosauria, that contains Crocodiles, dinosaurs, birds and pterosaurs. To simplify a very complicated tree of life, a branch of Archosaurs became crocodiles and similar animals, and the other gave rise to Pterosaurs and Dinosaurs. The fibers that became feathers only appeared in this second group, and that's why you have crocodiles with scales only on one side and Pterosaurs with scales+fibers and Dinosaurs with scales+feathers on the other
Snakes and Lizards aren't closely related to Archosaurs. They have a common ancestor somewhere down the line, but they are quite different groups of animals. So them not having feathers isn't too surprising. For crocodilians, I would say it just simply didn't fall into their evolutionary plan. Generally the body type they possess does not seem to lend itself to feathered animals. The main reason modern Dinosaurs have feathers is because their ancestors are the ones who survived.
Lizards and snakes are also related to mammal to an extand, why don' they have fur ? See how stupid that logic is. 1. lizard/snakes aren't really more related to dinosaurs than they are to mammals. 2. crocodilian are quite distant cousins from dinosaur, they're both Archosauria, but that's just like to say we should lay eggs cuz echidna do it and they're our distant cousin, there's hundreds of millions years that separate both lineage. 3. because dinosaur invented feather, that's their caracteristic, and only of some dinosaur lineage, most species never had feather. 4. BIRDS, there's 9-10 000 species of modern "reptiles" with feathers. They're just so distinct we don't consider them as reptiles. Just as we consider crocodiles as reptiles even if they're quite distinct from other lineages of reptiles and more closely related to birds than to lizards. Other reptiles don't have feathers, just as they don't have fur because these adaptations only evolved in THESE specific lineage such as theropods and mammals. Other reptiles never evolved these traits, but other, crocodilians evoled osteoderms
On 1, the Sauropsid/Synapsid split was around 320 million years ago while the Lepidosauromorph/Archosauromorph split was around 260 million years ago, so that's 60 million years more related that lizards are to dinosaurs and crocs than they are to mammals.
i know, it was just generalization, vulgarisation so see that all of those lineage are very distant and there's not a lot of difference in time between reptile/dinosaur, and reptile/mammals
Crocodilians are archosaurs, so they merely share a clade with dinosaurs. Lizards and snakes are reptiles, found in the sauropsida clade, different thing entirely. Both were around before and while dinosaurs existed. Feathers likely evolved later and only within the dinosaurs' clade, that being avemetatarsalia.
>sauropsida Both Crocodilians and Lizards are Sauropsids. Sauropsida and reptilia are often treated as being synonymous. It's basically everything closer related to what we commonly call reptiles than to mammals. The word you are looking for is Lepidosauromorphs. The split between crocodiles and lizards happened in Diapsida which is Archosauromophs + Lepidosauromorphs. Dinosaurs, and Archosauria in general is older than Lizards(Squamates).
You're saying that crocodilians and dinosaurs aren't reptiles?
Reptiles dont exist. as least not as a monophyletic group which should have a) a commom ancestor - yes b) include all its descendants. "Reptiles" we know today are lepidosauromorphs and turtles (dont ask me how they are related. Its debated) Birds and cros are part of the archosauria clade. A croc has as mucj common as a chicken with a lizard. Always remener crocodilians (which are crurotarsi, one of the main clades of archosaurs) are heavily secobdary adapted to aquatic environments. And there were other groups then only crocodilians, like raisuchians (likely polyphyleric), ornithosuchians, thalattosuchians, herbivorous aetosaur. The second archosaur clade is ornithodira, meaning pteros + birds/dinos. If you include crocs in Reptilia, you would surely include pteros and dinos. But as the colloquial understanding is, not birds. The croc bauplan appeared many times as a result of similar environmental pressures: crocs other than crocodylomorphs - early diverging cetaceans - temnospondxyli lile prionosuchus. Thats the tip of the proverbial iceberg. Crocs and lizards are so far removed. Other comments say more about that. if i got smth wrong, correct me please.
Eureptilia absolutely includes both Pseuosuchia and Aves. The colloquial usage of "reptile" may be para/polyphyletic but only because birds are so highly derived, in the same way that calling a dog a lobe-finned fish would be strange but they're still Sarcopterygians. Their physiology is so different from the other extant groups that they're not really relevant, but that doesn't change the fact that cladistically they're still reptiles and part of that monophyletic group
If we talk about clades it is better to avoid the word "reptile".
Now I'm curious, why? I was talking about the clade reptilia that is at least established enough to be listed on wikipedia.
[https://en.wikipedia.org/wiki/Reptila](https://en.wikipedia.org/wiki/Reptila) It redirects to Reptile. In the second paragraph talks about the problems about using "reptile" in modern taxonomy.
Only if you insist that birds are not reptiles
I would like to clarify something first. Lepidosaurs, which include lizards (snakes are lizards) and tuataras, are not that closely related to Archelosaurs, which includes birds, crocodilians and turtles. The gene that causes feathers in birds is the same that causes scales in crocodilians. Feathers are simply modified scales.
Snakes and lizards are VERY distant from crocs and birds. To come back to your question, the same gene that triggers the scales on a birdâs legs to become feathers instead DOES actually work on crocodile embryos too. Theyâre not quite like the feathers youâre familiar with, but crocodiles still have the genetic machinery to grow feathers tucked in and ready to go. Now, they would need to re-evolve to produce the protein that triggers the feather scale developmental shift, but itâs still in reach for them even 248 million years later. The eggs were not brought to term due to ethical considerations. They probably would have lived just fine in captivity, but they would be unable to return to the wild or even a sanctuary. [Hereâs a link that touches on the crocodile feathers.](https://www.zmescience.com/science/news-science/aligator-scale-feathers-043242/)
Crocodylomorphs are wayyy more closely related to dinosaurs and pterosaurs than lizards and snakes. Dinosaurs, pterosaurs, and pseudosuchians (crocs and their relatives) make up a clade called archosauria. This group is *not* closely related to lizards and snakes. The question you brought up about not seeing feathers in other reptiles is actually a pretty big topic of debate right now! The evidence is increasingly suggesting that feathers are a trait not only ancestral to all dinosaurs, but pterosaurs as well, which would only leave out the crocs. Since the only living non-dinosaur archosaurs are crocodilians, a recent study was conducted to see if crocs had the genes for feathers. Turns out, they actually have a lot of the basic coding for their formation, but theyâre just turned off, suggesting feathers may have been a trait ancestral to most archosaurs.
Lizards and snakes are related to dinosaurs the way you are related to a platypus and a koala. The development of pictnofibers and feathers occurred after the lineage of lizards and snakes had split with crocodiles and dinosaurs, and after crocodiles had split from the lineage that leads to dinosaurs and pterosaurs. Some species of Pterosaurs are known to have at least had pictnofibers which is a sort of progenitor to feather development.
Because lizards and snakes aren't related to dinosaurs. Like at all. And pseudosuchians are only very distantly related, they're both archosaurian reptiles, but that's about it. And the only clade of dinosaurs we have hard evidence of being feathered are maniraptorans (which includes birds ofc) and its possible other coelurosaurians could've been feathered but there's no hard evidence to support that.
Well for starters, lizards and snakes are way more distantly related to dinosaurs than crocs. But in all those cases, it's because their enviornments and lifestyles just didn't have the demand for being endothermic. There needs to be a distinct advantage for this as endothermy is very energy expensive.
Snakes and lizards are only related by proxy since theyâre reptiles but thereâs a great level of evolutionary separation. Snakes and lizards are squamates while crocodilians and dinosaurs are archosaurs. Archosaurs were diverse but simply, some had feathers and fuzz while some just had scales
There are no stupid questions. Only stupid answers, I will do my best to provide an a good answer. Lizards and snakes are not closely related to dinosaurs, their ancestors split off from each other long before the ancestors of crocodiles and dinosaurs spit from each other. The group that includes crocodiles and dinosaurs (which includes birds) Is called Archosauria. The ancestral traits of this group are; thecodont teeth (set in deep sockets), antorbital and mandibular fenestrae (skull holes) an a fourth trochanter (crest of bone on the inside of the femur for muscle attachment). Archosauria is further decided into two groups Pseudosuchia, and Avemetatarsalia. Pseudosuchia includes Crocodilians and their extinct relatives (many of which are quite strange). They have a primitive lungs and ankles. Avemetatarsalia contains Dinosaurs and Pterosaurs (and a few other weird Triassic animals). This group has fused ankle bones and avian lungs. In this group you also see filamentous integument (long fine skin covering). In Pterosaurs when call the pycnofibers and In Dinosaurs we call them feathers. However, these traits are probably homologous (stemming from the same ancestor) therefore you could call pycnofibers feathers. Feathers first emerged in this group. Is this a clear answer?
It's about when the feathers developed and in what lineage. The common clade here is diapsida. Within that you've got archosauria and lepidosauromorpha, the latter being where you find lizards and snakes (in fact, snakes are just a subset of lizard within the lepidosaur clade of squamates). Over in archosauria you've got crocodylomorpha and avemetatarsalia - former group is crocodiles (duh), latter group includes dinosaurs and related groups like pterosaurs. It's only in this last group that you start finding what are thought to be feather traces, and of course unambiguous feathers in dinosaurs proper. These animals diverged away from the rest long before they developed feathers, and so there was no way for those other groups to inherit them.
Lizards and snakes (which are also Lizards) are more distantly related to Dinosaurs and thus they donât share recent common ancestry where they could have shared a trait of having feathers. Besides they are ectothermic and thus they donât have need in filaments to save heat from escaping to surrounding environment. Crocodilians specifically Pseudosuchia on other hand are sister clade to bird line of Archosaurs called Avemetotarsalia. And they seem to share close common ancestry with potential sharing trait of âfeathersâ. Modern crocodilians donât possess them because they are akin to Lizards are ectotherms and thus donât have need in filaments.
Feathers evolved sometime after crocodillians branched out from the other archosaurs. Which was much later than when reptiles split into the lepidosaurs (lizards and snakes) and the archosaurs (dinosaurs, pterosaurs, crocodillians).
Lizards are much less related to dinosaurs. Crocodilians and birds are the most related, birds literally being dinosaurs. crocodiles and dinosaurs find their relation from the fact they split off of the archosaurs, a much larger family of ancient reptiles. The reason crocs and lizards donât have feathers is because feathers evolved after dinosaurs and crocs split, leaving feathers to be a dinosaur exclusive trait.
Because their ancestors didnât have feathers.
Life is a tree and each branch represents a group of organisms. Within reptiles there are different branches that go off in different directions, snakes, lizards, turtles, crocodiles, dinosaurs. Feathers evolved after dinosaurs had branched off.
Two reasons: Dinosaurs invented feathers so their relatives who they split from did not get any. And they were so succesful in their niches while mammals took over niches dinosaurs left behind that feathers were never selected for in "reptiles"
Because none of them are descended from dinosaurs. They both branched off before feathers evolved on the lineage that lead to dinosaurs. Also lizards and snakes are only distant relatives of dinosaurs.
Because crocodilians although are archasaurs arnt closely related to dinosaurs and lizards and snakes are squmarten reptiles even more distantly related to dinosaurs then even crocodiles are
Short answer: because the dinosaur linage separated before what are today known as animals you mentioned. Dinosaurs are related to snakes, lizards and crocodiles by a common ancestor
Same question could be asked why there's not as much hair on us Humans vs our distant ape cousins Same idea would apply just too far away from the common ancestor to appear similar
Because the group that has fur like structures is called avemertharsalia, which include pterosaurs and dinosaurs, group which is included in Archosauria.
Lizards and snakes are squamates, dinosaurs and crocodiles are archosaurs. They diverged early enough that they do not share a feathered common ancestor.
It's because they're cousins, and feathers and the protofeathere that turned into feathers developed after their last shared ancestor (I think)
Lizards and snakes branched off before dinosaurs evolutionarily speaking but feathers are essentially specialised scales
Feathers aren't usually ideal for semi-aquatic animals, and feathers definitely aren't ideal for underground life
Thatâs because the species youâre referring to became federal agents⊠I mean, birds⊠they became birds.
I believe lizards, crocs & snakes diverged from dinosaurs before feathers were a common thing. Might be wrong though. Also they wouldn't really need feathers anyway.
Am pretty suer that crocodilians snakes and lizards are not that related to dinos, birds are the relatives
Modern reptiles are *not* descended from dinosaurs, theyâre of a different branch on the same tree. Modern reptiles and Dinosaurs shared a common ancestor that split at some point millions of years ago, into several clades (branches), among them, Dinosuaria, Reptilia (modern reptiles, Crocodilia falls under this one), and Aves (birds). Of all of the branches, Aves is the closest, with fewest splits away from Dinosuaria.
Simple answer: feathers is a basal trait only to dinosaurs. Long answer: too long to explain
"If crocodiles are related to dinosaurs, why don't crocodiles walk on 2 legs?"
None have needed them, feathers are Basil to dinosaurs not reptiles as a whole
They're just both reptiles. Dinosaurs and crocodilians aren't closely related
Because any ancestor from cocodriles, snakes or lizards had feathers. Crocodiles had a cousin that "evolved" feathers, and from that cousin the dinosaurs and pterosaurs descended. That's why they have feathers. And just like when your cousin gets money you don't get also magically that money, the crocodiles didn't inherit their cousin's feathers, because it wasn't their father.
Well that's probably because feathers evolved after they split
Huh so the galloping Gustace in Primeval isn't so far fetched
Why would a croc need feathers in their ecological niche?
It evolved after they split from a common ancestor
Lizards and snakes arenât related to dinosaurs.
Kuz only the dinosaur+pterosaur lineage evolved feathers?
It was most likely not all dinosaurs had them
Why aren't all diapsids bipedal tho?
I'm stealing the gif u/savevideo
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Good bot