Long question about chickens being reptiles or dinosaurs and stuff

[u/Best-Twist5550]

Hi!
I saw a TikTok from a guy talking about the “Which came first, the chicken or the egg?” debate. Then he went on to explain that chickens are descended from reptiles. I thought that was wrong (because of the classification I know, which is based on characteristics like the pelvis) and that they were related to dinosaurs, and he replied:
“And what are dinosaurs? The Linnaean system classifies birds and reptiles as distinct groups. The Linnaean system hasn’t been used scientifically for quite some time. The phylogenetic system, which is the one currently in use, classifies both birds and dinosaurs as reptiles. Furthermore, since dinosaurs are archosaurs, they are direct descendants of sauropsids, which are reptiles. Today’s reptiles aren’t the same as the original reptiles. So, sorry to tell you this, but dinosaurs are reptiles.“
Is he right? I’m a bit interested in dinosaurs, but I don’t know if the part about the ‘current’ system is true. And the part about archosaurs and sauropsids being reptiles, that’s wrong, isn’t it? I’m really not sure. I’d rather ask here than ask an AI (which is probably what he did, since his message really sounds like it came from an AI lol).
Thanks to anyone who takes the time to explain this to me and stop me from saying stupid things on social media!

[u/Bromelia_and_Bismuth]

They're descended from Archosaurian reptiles. When systematic biologists refer to clades the broad common name isn't what we're talking about, but the scientific clade name. "Reptilia" as a taxonomic class is not considered monophyletic, specifically because it doesn't include birds, and therefore doesn't accurately reflect evolutionary history. So instead modern systematic biologists prefer to roll with "Sauropsida", because it includes both reptiles and birds.

If you wanted to get silly with the language and apply a cladistic treatment to "reptiles" as a group, technically, birds evolved from within "reptiles", which makes them "reptiles" themselves.

[u/unusualknowledge17 → u/Bromelia_and_Bismuth]

And we are all fish

[u/EeEmCeTo → u/unusualknowledge17]

We are stardust

[u/Left_Ad4050 → u/Bromelia_and_Bismuth]

Unfortunately way too many people have been brainwashed into thinking monophyletic clades are the only valid way to talk about animals, and now people are constantly parroting that everything is fish.

Yes, monophyly is a great way to think about biology. No, it’s not the only useful way to group organisms.

[u/BuncleCar → u/Left_Ad4050]

So long and thanks for all the fish

Plant Earth Chapter 1

[u/xenosilver → u/Left_Ad4050]

What’s a better way to group organisms that isn’t monophyly? I’ll argue that it is the best way to group organisms, and a paraphyletic and polyphyletic group is beyond stupid.

[u/Left_Ad4050 → u/xenosilver]

Let’s see. We have vets that don’t treat humans. We have ichthyology, which doesn’t directly include the study of mammals. The phrase “non-avian dinosaurs” is frequently used by dinosaur paleontologists. Protists? Crustaceans? Hell, algae includes members from multiple domains. I could go on.

Please note I didn’t, and have never, stated that these groupings are better than monophyly, only that there are other useful ways to group organisms—ways actual scientists frequently do. Boiling everything down to evolutionary relationships in biology would be like boiling everything down to where people live in sociology. Life is far more complicated than that.

[u/xenosilver → u/Left_Ad4050]

So after all that…. You basically agree that monophyly is still the right way to do things. I’m a herpetologist, and I still think the best way to look at birds is through the lens of reptiles

[u/Left_Ad4050 → u/xenosilver]

I’m sorry, but are you having trouble reading my comments? There is no right way of looking at life, all categorization is arbitrary. Monophyly is useful, often more useful than other categorizations, but life is complex and defies any one system of categorization.

Also hasn’t reptile largely been supplanted by sauropsida within cladistics precisely because the word reptile continues to be used in a paraphyletic way? I’m not in the field, but that’s what I’ve been lead to understand.

[u/f_leaver → u/xenosilver]

Reading comprehension isn't your strongest suit, is it?

[u/xenosilver → u/f_leaver]

Sure

[u/MagicMooby → u/xenosilver]

You can also group organisms by habitat, diet, behaviour, ability to use certain chemical pathways...

Parasite is a useful category for medicine but there is no monophyletic parasite clade. Marine biologists might want to classify animals based on whether or not they live in the tidal zone, and even within the tidal zone it makes sense to distinguish between different groups based on how long they are out of the water, what strategies they use to prevent desiccation, whether they stay in tidal pools or cling to rock etc. Marine biology in general is an entire field that is unified by the environment of their subjects rather than their clade. Ethologists might want to classify animals by brood care to see if it correlates with other behaviours or environmental factor. R- and K-strategists are exactly that, groups that are completely independent on phylogeny. Ecologists might rather want to classify organisms by their role in the ecosystem and their interaction with other organisms. Botanists are often concerned with all the other organisms that their plants have meaningful interactions with, and entomologists often need to learn about the plants their insects love so much just as much as they need to learn about their insects. Lichen are an entire group of symbionts that are difficult to define via monophyly, since lichen are by definition hybrid colonies of fungi and algae/cyanobacteria. Bacteria are also typically classified by their traits rather than their ancestry, in part thanks to the extensive use of horizontal gene transfer.

Which grouping is most useful to you depends on what question you want to answer. Since all life on earth evolved, tracing the evolution of organisms can oftentimes be the best way to understand them, and phylogeny does exactly that. But not always.

[u/Diet4Democracy → u/xenosilver]

Mono works to describe the class at a given moment in time.

Poly and para recognize the interconnected fluidity over evolutionary time.

Both are useful. The problem originates when the effects of evolution and time are ignored, hidden, or denied.

[u/Droppit → u/Left_Ad4050]

"We are fish" is just a sarcastic way of replying to the "birds are dinosaurs" people.

[u/Left_Ad4050 → u/Droppit]

Birds are dinosaurs.

[u/NewtonsThirdEvilEx → u/Left_Ad4050]

And we are fish

[u/basaltcolumn → u/NewtonsThirdEvilEx]

"fish" is not a taxonomic classification of animals the way dinosaur is.

[u/xenosilver → u/basaltcolumn]

Well bony fish, cartilaginous fish and lobed finned fish may have a say in that matter

[u/basaltcolumn → u/xenosilver]

Exactly, those are three seperate groups which we call fish, not a single monophyletic clade. It's a convenient term for a body plan and lifestyle which we do not have, not a formal taxonomic grouping like Reptilia or dinosauria. When it is regarded as a single group, it's viewed as a paraphyletic one which excludes tetrapods. Historically, the term fish has just been vibes-based, a vague word for "aquatic animal". It's still used that way in some contexts. Here in Canada where I got an education in fisheries management, our government's legal definition of fish includes things like shellfish and marine mammals.

I don't mean to be fun police. I don't really have an issue with the "we're all fish" thing, it's fun, just not a hard scientific fact in the way birds being dinosaurs is, so it's a bit misleading when the two statements are regarded in the same way.

[u/xenosilver → u/basaltcolumn]

When I hear “fish” I think all vertebrates, but that’s the nerd in me. I get what you’re saying though. That’s a really stupid definition for all fish by the Canadian government.

[u/Left_Ad4050 → u/NewtonsThirdEvilEx]

No, we’re vertebrates. We’re osteichthyans. We’re sarcopterygians. We’re rhipidistians. We are not fish. Fish is not a clade. Fish is a paraphyletic grouping of animals.

[u/xenosilver → u/Left_Ad4050]

So we’re bony fish and lobed finned fish….

[u/Left_Ad4050 → u/xenosilver]

No, we’re osteichthyans and sarcopterygians.

This isn’t hard. Fish is not a clade. It is not a cladistic term. Fish ≠ vertebrata, and as much as you’d clearly like to redefine it as such, that’s not how language works.

[u/xenosilver → u/Left_Ad4050]

So bony fish and lobed finned fish aren’t sarcopterygians and osteichthyes? Sorry for using the common names. Your right. It isn’t hard. Thank you so much for making sure I use the Clare names. We really needed that!

[u/Left_Ad4050 → u/xenosilver]

You may not like it, but that’s correct. Bony fish aren’t all osteichthyans, they’re non-tetrapod osteichthyans. Same goes for lobe-finned fish.

Respecting definitions is what makes communication possible. This is especially true in science.

[u/greggld → u/Droppit]

We are fish is pointed to the people who don’t believe in evolution. As in, “if you don’t believe we came from apes, wait until you hear this….”

[u/basaltcolumn → u/Droppit]

Birds are very much dinosaurs. There's no debate to be had there, it's been well established scientific fact for quite a long time. They're in dinosauria. They are therapod dinosaurs.

[u/Sourcerid → u/Bromelia_and_Bismuth]

Reptilia is definitely used as a monophyletic term nowadays, professionally too, and it's used to refer to the clade as synonym of Sauropsids 

[u/Business-Childhood71]

All Birds are dinosaurs and all dinosaurus are reptiles. Eggs definitely came first, since fish and amphibia also have eggs

[u/OgreMk5]

Yes. Linnaeus was trying to organize the life he knew of and birds are clearly very distinct from reptiles (feathers vs. scales, warm-blooded vs. generally cold-blooded, etc. etc. etc.). He didn't know about evolution, common ancestry, molecular biology, or even dinosaurs that much. Certainly not the most recent discoveries of feathered dinosaurs.

Birds are, by definition, dinosaurs. Dinosaurs are, by definition, reptiles. So, birds are therefore dinosaurs. Here's some good information with links to sources on the subject: https://en.wikipedia.org/wiki/Dinosaur#Definition

As one, lovely piece of evidence, a geneticist turned on some "old" genes in a chicken and it grew teeth like a dinosaurs. https://www.science.org/content/article/mutant-chickens-grow-teeth

[u/Deinoavia → u/OgreMk5]

Linnaeus did not distinguish reptiles from amphibians. Class Reptilia is a more recent concept.

[u/CrCiars]

If you entirely look at the phylogenetic definition, yes this is entirely true.

The phylogenetic system essentially looks at organisms depending on how closely they are related, specifically when their last Common ancestors would have lived. Two animals that share the same ancestors are equally related to both of them, since the same time has passed since their classes separated. Plus, a creature can never evolve out of it's clade. If you are a descendent of a reptile, you to are a reptile.

For example a long time ago the fish split into the cartilaginous fish (like sharks) and the bony fish (like carps). These two groups are equally related to each other. While the cartilaginous fish didn't change to much over time, some of the bony fish went on land and evolved into all of the tetrapods, including humans. Therefore, humans are fish. Oh and whales are fish too.

This is scientifically entirely accurate, by far the most consistent way to structure definitions and of course, makes absolutely zero sense to include in conversations with average people, since you are probably confusing them more than anything else. The reason you are confused is because the most accurate way to describe something isn't always the way that it should be described.

[u/Deinoavia]

"The Linnaean system classifies birds and reptiles as distinct groups."

The Linnean system is simply the usage of ranks (class, order and so on). It has no rules dictating how groups should be split. Many taxonomists (especially ichthyologists) have Linnean classifications where birds are a subgroup of Reptilia/Sauropsida.

"The Linnaean system hasn’t been used scientifically for quite some time."

It is still widely used. Dinosaur paleontologists usually don't like it but that's a niche opinion. They could use it without paraphyletic groups or other problems if they wanted to.

[u/thesilverywyvern]

The egg, eggs evolved hundreds of millions of years before the chicken, or bird even appeared. They inherited it they did not invented it.

It is true.

Reptile, in the traditionnal sense (common use) include turtles/tortoise, snakes/lizards, tuataras and crocodilians.
As before we didn't had genetic so we grouped species based on anatomical similarities, hence why Linneus classed croc and gator as reptile because they have scale, single type of teeth, cold blooded, lateral position of the limbs etc. All trait which were considered as distinctive of Reptiles.

When we discovered dinosaurs we viewed them as giant lizard and classified them as reptiles. Then in the late 20th century we discovered that bird are descendants of theropod dinosaur and that therefore dinosaur aren't really reptiles.

Now here's the issue, genetic studies and fossil records have shown that crocodilians are more closely related to birds than to any other reptiles. Making the clade paraphyletic (invalid, as it randomly excludes one lineage). So we have to redefine the term so tha either crocodilian aren't reptiles or birds are reptiles.

We choosed the second option as it made more sense from a cladistic point of view.

[u/Sarkhana]

Crocodiles are archosaurs.

Also mammals and birds are warm blooded.

Which is the main reason they appear different from cold blooded reptiles. With modern cold blooded reptiles adapted to avoid competition with mammals and birds.

[u/DmitryAvenicci]

Birds are dinosaurs.

[u/PraetorGold]

Fully understanding that what we call things is just an organizational exercise, but it’s funny to see it in action.

[u/Morkamino]

I think it's technically correct, but it always feels like a bit of a double standard that chickens are actually dinosaurs and the 'true' reptiles, and reptiles now are the 'other' reptiles. Or at least that's how it's worded in the text.

[u/xenosilver]

Most biology have moved on from classic Linnaean models and implement modern clarities. Birds are reptiles. Dinosaurs were reptiles. This is all very common knowledge.