That would mean…not very. Reptiles are an extremely broad and diverse group, containing everything from penguins and crocodiles to tuataras and pythons. Mammals are the most closely-related extant clade that is generally not considered “reptile”, to reptiles.
Arachnids, on the other hand, are more distantly related to insects. Crustaceans form their closest relatives, followed by myriapods (centipedes & millipedes). Only then do arachnids appear.
Yup. Birds are reptiles! If you want to define a monophyletic clade that includes crocodiles and lizards, there is no way to do that without also including birds. To define a clade, you take the evolutionary tree and make a “cut” somewhere on it. Everything below that cut is part of the same clade, you can’t selectively remove some branches but not others, unless it’s by changing where you make your single cut.
So in this diagram:
The green circle notwithstanding, you would usually define reptile as a cut at the “C” on the diagram. You could put the cut at Lepidosauria, but that would mean crocodiles and turtles are no longer considered reptiles either.
A more zoomed-in look would show that after crocodiles and birds branched apart, you also get another branch where pterosaurs branch away from dinosaurs, and that birds are one of many branches and subbranches of dinosaur.
I really appreciate the info and the way you laid it out. Just curious, is that knowledge part of a hobby and/or career? Or was that like just one of the random tidbits you picked up somewhere?
Yeah just a casual interest. Not enough that I’d really call it a hobby, and certainly not a career. But a little more than a few random titbits. This video’s not a bad quick intro to the reasoning I used in my previous comment.
Reptiles, as traditionally defined and therefore as usually meant, do not include birds or mammals. It’s a paraphyletic classification (of which there are boatloads).
Mammals, Birds and therefore non-mammal, non-bird amniotes (reptiles) are class-level classifications, as are insects and arachnids.
Sure, but we’re having this conversation in 2025, after phylogenetic classification has long since taken over as the way we describe the relations between species.
Birds are unambiguously reptiles.
Mammals are not reptiles, but are the most closely-related animals to them.
Who is “we”? It certainly isn’t most people. It’s like these interminable “no such thing as a fish” bollocks. Or “AcKsHuAlLy bananas are berries OHOHOHOHO.”
Keep that kind of jargon for your academic articles. In pop-sci contexts like here, it’s not unreasonable to use, but it deserves a health warning because of the intersection of audiences. Insisting that there’s only one correct usage is insufferable.
They’re separate biological classes.
So they’re about as far apart as you are from a reptile, bird or fish.
No, because spiders are super many, tiny, and scary, exactly like insects.
Lembot_0006 is orders of magnitudes larger than most reptiles, and is one of a kind.
I expect to lose this argument, but mom didn’t raise no quitter.
That would mean…not very. Reptiles are an extremely broad and diverse group, containing everything from penguins and crocodiles to tuataras and pythons. Mammals are the most closely-related extant clade that is generally not considered “reptile”, to reptiles.
Arachnids, on the other hand, are more distantly related to insects. Crustaceans form their closest relatives, followed by myriapods (centipedes & millipedes). Only then do arachnids appear.
Hold on…
Yup. Birds are reptiles! If you want to define a monophyletic clade that includes crocodiles and lizards, there is no way to do that without also including birds. To define a clade, you take the evolutionary tree and make a “cut” somewhere on it. Everything below that cut is part of the same clade, you can’t selectively remove some branches but not others, unless it’s by changing where you make your single cut.
So in this diagram:
The green circle notwithstanding, you would usually define reptile as a cut at the “C” on the diagram. You could put the cut at Lepidosauria, but that would mean crocodiles and turtles are no longer considered reptiles either.
A more zoomed-in look would show that after crocodiles and birds branched apart, you also get another branch where pterosaurs branch away from dinosaurs, and that birds are one of many branches and subbranches of dinosaur.
I really appreciate the info and the way you laid it out. Just curious, is that knowledge part of a hobby and/or career? Or was that like just one of the random tidbits you picked up somewhere?
Yeah just a casual interest. Not enough that I’d really call it a hobby, and certainly not a career. But a little more than a few random titbits. This video’s not a bad quick intro to the reasoning I used in my previous comment.
Reptiles, as traditionally defined and therefore as usually meant, do not include birds or mammals. It’s a paraphyletic classification (of which there are boatloads).
Mammals, Birds and therefore non-mammal, non-bird amniotes (reptiles) are class-level classifications, as are insects and arachnids.
Sure, but we’re having this conversation in 2025, after phylogenetic classification has long since taken over as the way we describe the relations between species.
Birds are unambiguously reptiles.
Mammals are not reptiles, but are the most closely-related animals to them.
Who is “we”? It certainly isn’t most people. It’s like these interminable “no such thing as a fish” bollocks. Or “AcKsHuAlLy bananas are berries OHOHOHOHO.”
Keep that kind of jargon for your academic articles. In pop-sci contexts like here, it’s not unreasonable to use, but it deserves a health warning because of the intersection of audiences. Insisting that there’s only one correct usage is insufferable.