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Post by 0ldgrizz on Nov 24, 2014 15:00:58 GMT 5
Some paleontologists argue that dinosaurs were not reptiles. I have to agree with them. I believe that dinosaurs evolved from reptiles, as did mammals and pterodactyls. But, dinosaurs were warm blooded animals. To say that a dinosaur is a reptile is calling birds reptiles.
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Post by theropod on Nov 24, 2014 15:47:37 GMT 5
 Palaeontologists don’t argue that dinosaurs were not reptiles. In fact, no serious researcher living in the 21st century would do that. It’s now consensually accepted that reptilia should have a monophyletic definition and hence include all its descendants. Dinosaurs evolved from reptiles, therefore they are reptiles themselves. Their metabolism is irrelevant to their phylogenetic position. Mammals did not evolve from reptiles, but from synapsids–they therefore are not reptiles, but synapsids. Birds and pterodactyls are both reptiles (dinosaurs to be exact in the former case). That they are "warm blooded animals" does not mean they are not reptiles–throughout evolution there have been many endothermic reptiles besides dinosaurs (sauropterygians, ichthyopterygians, pterosaurs, mosasaurs). If you were just trying to make a joke, I’m sorry  |
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Post by creature386 on Nov 24, 2014 23:33:12 GMT 5
0ldgrizzIs there any possibility that you use "reptiles" as a synonym for lizards + snakes+ crocodiles + turtles?
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Post by theropod on Nov 24, 2014 23:37:29 GMT 5
^it seems that way, but not as a cladistic expression, rather as exclusively the named taxa, i.e. a polyphylum.
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Post by creature386 on Nov 25, 2014 0:00:01 GMT 5
I remember old books of mine that used such a definition. These definitions are (mostly due to outdated sources) still in the heads of people, so it is possible that the OP is serious. Sometime ago, I seriously wondered if dinosaurs are reptiles.
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Post by Godzillasaurus on Nov 27, 2014 1:04:15 GMT 5
They are most definitely reptiles. I don't know why anybody, especially gifted paleontologists or zoologists, would ever deny that.
Birds, too, are sauropsids; frankly something like a bird should not be part of its own class.
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Post by Godzillasaurus on Nov 27, 2014 1:07:52 GMT 5
So did mammals; are they reptiles? I agree that it is a stupid notion to think that dinosaurs are not reptiles, but this argument does not make sense. Amphibians also evolved from fish, so does that make them fish?
A synapsid is simply a grouping of animals based on skull anatomy: archosaurs and lepidosaurs are diapsids while turtles are anapsids. And note that synapsids too would have evolved from more basal lifeforms as well, whether or not you classify them as a group outside of reptilia
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Post by 0ldgrizz on Nov 27, 2014 1:29:41 GMT 5
So, you are saying that dinosaurs and birds are warm-blooded reptles? Birds are theropods; coelurosaurs. Are you then classifying birds as reptiles?
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Post by Godzillasaurus on Nov 27, 2014 1:35:17 GMT 5
Are you talking to me or theropod? Because the content of his post correlated more directly with what you are asking, yet you seem to be replying to me.
If you are talking to me, then my answer is YES. Birds should not be classified in their own class (example: mammalia is a class), but rather as an order within reptilia (after all, their closest modern relatives are crocodilians which are also reptiles).
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Post by Infinity Blade on Nov 27, 2014 2:05:47 GMT 5
No they didn't.
I'd say hypothetically speaking, even if mammals did evolve from reptiles (which they didn't), they actually would be considered reptiles, no matter how much one would find that baffling and/or ridiculous.
They're a valid clade of animals though, are they not?
Tell me, what of the other idea that turtles are diapsids that simply lost the default diapsid skull characteristics (ergo they only look like anapsids at first glance but are really derived diapsids)?
Yeah, they evolved from (basal) amniotes, as did sauropsids.
You mean tetrapods evolved from vertebrates? You know "amphibians" and "fish" are paraphyletic groups (and really, colloquial terms) that aren't exactly seriously used by scientists, right?
Oh and just in case (as I'm a bit paranoid as to how ambiguous this post may be to readers in terms of its "emotion"), I'm not angry or trying to be aggressive here.
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Post by theropod on Nov 27, 2014 3:18:33 GMT 5
So, you are saying that dinosaurs and birds are warm-blooded reptles? Birds are theropods; coelurosaurs. Are you then classifying birds as reptiles? Exactly! Godzillasaurus: That wasn’t just my fantasy, it’s the generally accepted terminology. Within Amniota there are two clades, the Sauropsida (which is a synonym of reptilia, all descendants of the most recent common ancestor of Passer domesticus and some turtle) and the Synapsida (which is the clade encompassing all amniotes that share a more recent common ancestor with us than they do with reptiles). As it happens, the layout of the cranial fenestrae happens to be a feature of this group, but that’s rather a side issue. Amphibians and fish are not valid clades, and actually both should be marked by quotation marks when used in a scientific text (hence "pisces"). Nobody is considering us "fish" because nobody actually uses "fish" any more ("Why?" you might ask. It’s because they never seem to have had a proper definition other than "some vertebrates that aren’t tetrapods, maybe gnathostomes if I’m feeling like it today, maybe also non-gnathostomes"). On the other hand, you should get used to the concept of being a bony fish, a sarcopterygian to be exact. That might not be so difficult because the vast majority of fishes as we know and eat them can be resumed in the clades of actinopterygia and chondrichthyes, which we luckily aren’t part of (and neither are elephants or pterosaurs for that matter). Infinity Blade: Yes, Synapsida is a valid clade, that’s why mammals are Synapsids. The problem I think arises from old-fashioned people still calling them "mammal-like-reptiles", which is frankly just as unscientific as it is inaccurate. Depends on the definition of Amniota, if it’s node based, there’s just one basal amniote and all others are either reptiles or synapsids. Somehow that definition seems the most intuiitive to me (it’s independent of how ), but that’s just my opinion. |
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Post by Godzillasaurus on Nov 27, 2014 21:10:41 GMT 5
Yes they did. You are forgetting that mammals too are synapsids. A synapsid is a grouping of animals based on skull morphology and should not be offshooted into its own class.
They are? They have characteristics that completely constitute them in their own class? That is like saying that only diapsids were reptiles; turtles are anapsids yet are still reptiles. And even if primitive synapsids and modern mammals are part of their own separate class, they would have still evolved from more primitive lifeforms in the first place. So your argument still does not hold true.
Possible, but unconfirmed. Including anapsids as reptiles and early synapsids like dimetrodon as their own clade does not make sense, especially when the latter possessed very reptile-like characteristics albeit much more mammal-like tooth arrangements and such.
You are missing the point... I do not believe that there has been ANY studies confirming the existence of new chordate classes (such as simply basal amniotes). Evidence shows that the first true chordate (which still lacked a true spine, BTW) was a fish. And soon these primitive fish evolved air-breathing/terrestrial capabilities and gave rise to amphibians, which in-turn soon developed more hardy eggs that could be laid outside of water. While early diapsids gave rise to both archosaurs and lepidosaurs, basal synapsids would have done the same to mammals.
Unfortunately, this still does not mean a thing. Tetrapods evolved from vertebrates consisting of very primitive fish species (ones that lacked a true skeleton; like lampreys or hagfish), yes, but these chordates during the time of anomolocaris (Cambrian) were, simply, FISH. These classes that evolved over time only kept evolving and differentiating as time went on, but they were still the same general class.
I think I can see where you are going, but unfortunately I still cannot quite see where the difference between "reptiles" and synapsids comes into play. They may be different clades entirely, sure (consider how these early synapsids were more closely related to mammals than archosaurs, lepidosaurs, or turtles), but that does not refute the notion that they may, in fact, simply be "reptiles" that evolved into modern mammals during the Mesozoic, as inaccurate as you may deem it.
Cladistics like this are confusing, but in broader terms, early synapsids could have very well still been "reptiles", as could the most basal chordates still be "fish", even if their characteristics define them very clearly outside of modern fish orders. It is all about how broad or specific you intend to make it.
Exactly, and the same can be said about diapsids, anapsids, and euryapsids (ichthyosaurs and sauropterygians); whether or not some characteristics were developed and/or lost during speciation, they are all still "reptiles" in the broad sense.
Cladistically, you are correct, but, again, think about what I said earlier. Clades define relationships between different animal groups, whereas "classes" are simply to describe characteristics, in which case earlier synapsids could still be considered "reptiles"
You see? I am not implying that early synapsids were more closesly related to diapsids for example than to mammals (which is fundamentally incorrect, so we all win here), but just that, when ignoring simple relationships, they could have still been "reptiles" in the traditional defintition of the word.
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Post by creature386 on Nov 27, 2014 22:33:42 GMT 5
Yes they did. You are forgetting that mammals too are synapsids. A synapsid is a grouping of animals based on skull morphology and should not be offshooted into its own class. Incorrect. Synapsida is a monophyletic clade that is used in scientific classifications, it is no wastebasket for animals with a certain skull shape. That skull shape is a monophyletic trait. Here a fairly recent paper that uses Synapsida:  www.stuartsumida.com/BIOL622/ReiszEtAl2009.pdfSynapsida are a sister clade to Diapsida and they together form Amniota. They are? They have characteristics that completely constitute them in their own class? That is like saying that only diapsids were reptiles; turtles are anapsids yet are still reptiles. And even if primitive synapsids and modern mammals are part of their own separate class, they would have still evolved from more primitive lifeforms in the first place. So your argument still does not hold true. The skull features of the synapsids qualify as a diagnostic feature, but remember that feature lists for phylogenetic decisions are always long and sometimes hard to find (when it is no newly described clade). Reducing decisions to one feature (e.g. "diapsids", "synapsids" and "anapsids" all have different skull openings and thus should either be equally ranked sister clades) normally doesn't work. There are probably reasons for putting diapsids and anapsids (rarely used term actually) in one clade. Possible, but unconfirmed. Including anapsids as reptiles and early synapsids like dimetrodon as their own clade does not make sense, especially when the latter possessed very reptile-like characteristics albeit much more mammal-like tooth arrangements and such. Actually, turtles being diapsids is far from nonsensical. There is molecular evidence for this claim: online-media.uni-marburg.de/biologie/biomedia_alt/private/Kurstage/Tag09_Sequenzanalyse2_FS-MK/Zardoya%20and%20Meyer%202001.pdfYou are missing the point... I do not believe that there has been ANY studies confirming the existence of new chordate classes (such as simply basal amniotes). Evidence shows that the first true chordate (which still lacked a true spine, BTW) was a fish. And soon these primitive fish evolved air-breathing/terrestrial capabilities and gave rise to amphibians, which in-turn soon developed more hardy eggs that could be laid outside of water. While early diapsids gave rise to both archosaurs and lepidosaurs, basal synapsids would have done the same to mammals. Define fish first. This is no phylogenetically valid term. For example bony and cartilaginous fish may share fish in their name, but they do not form a clade. Unfortunately, this still does not mean a thing. Tetrapods evolved from vertebrates consisting of very primitive fish species (ones that lacked a true skeleton; like lampreys or hagfish), yes, but these chordates during the time of anomolocaris (Cambrian) were, simply, FISH. These classes that evolved over time only kept evolving and differentiating as time went on, but they were still the same general class. Again, you need to say what fish means. Lampreys are no bony fish, but members of the disputed clade Hyperoartia, while the hagfish may have fish in its name, but it belongs to Craniate. I think I can see where you are going, but unfortunately I still cannot quite see where the difference between "reptiles" and synapsids comes into play. They may be different clades entirely, sure (consider how these early synapsids were more closely related to mammals than archosaurs, lepidosaurs, or turtles), but that does not refute the notion that they may, in fact, simply be "reptiles" that evolved into modern mammals during the Mesozoic, as inaccurate as you may deem it. Well, Reptilia and Synapsida both have solid definitions. My own definition of Synapsida is everything more closely related to a mice than to a lizard and for Reptilia you need to change the reference taxa. The definition works because both are regarded as sister taxa that create a clade called Amniota. BTW, there is also a node based definition that counts turtles as diapsids and uses Lacerta agilis and Crocodylus niloticus as reference taxa. Here the source: sysbio.oxfordjournals.org/content/53/5/815.full.pdfCladistics like this are confusing, but in broader terms, early synapsids could have very well still been "reptiles", as could the most basal chordates still be "fish", even if their characteristics define them very clearly outside of modern fish orders. It is all about how broad or specific you intend to make it. Looking like a reptile or like a fish is not the same as being one. Do you have an example of an early synapsid that could be called a reptile? Exactly, and the same can be said about diapsids, anapsids, and euryapsids (ichthyosaurs and sauropterygians); whether or not some characteristics were developed and/or lost during speciation, they are all still "reptiles" in the broad sense. What he means is that the sister taxon to Reptilia status of Synapsida is valid. Look at my cladogram above. Cladistically, you are correct, but, again, think about what I said earlier. Clades define relationships between different animal groups, whereas "classes" are simply to describe characteristics, in which case earlier synapsids could still be considered "reptiles" You see? I am not implying that early synapsids were more closesly related to diapsids for example than to mammals (which is fundamentally incorrect, so we all win here), but just that, when ignoring simple relationships, they could have still been "reptiles" in the traditional defintition of the word. The problem is that Reptilia is (contrary to what was claimed sometimes on carnivora) is a valid clade. The paper I posted as a source for the node-based Reptilia definition supports this. |
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Post by Infinity Blade on Nov 27, 2014 23:17:59 GMT 5
I think you summed that better than I could have creature.
Godzillasaurus, is this "broader sense" or "traditional definition" of "reptile" you're referring to the old trait-based definition of "reptile". Because if so, then sure, I suppose you could make it look as if mammals evolved from "reptiles" ("reptiles" in this sense/context referring to anything that fits the old trait-based definition of "reptile", ergo any tetrapod with scaly integument, ectothermy, and a sprawling gait), even though I'm not sure just how well the earlier synapsids mammals are derived from fit the trait-based definition of "reptile".
But that doesn't really matter much. I'm not referring to reptiles that way, I'm referring to the valid, monophyletic definition of reptile.
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Post by theropod on Nov 27, 2014 23:22:55 GMT 5
No, as a matter of facts Synapsida is a valid clade. Whjether you want to call it a class is your own choice, the traditional ranking system doesn’t work any more, although one could perhaps justify a ranking based on diversity instead… How so? His argument wasn’t that synapsids didn’t evolve from more primitive lifeforms. Every animal has developed from more primitive lifeforms. The point is that they are monophyletic. That has virtually nothing to do with whether or not they all have the same number of fenestrae.A synapsid could loose all of its fenestrae, it would still be a synapsid since it evolved from synapsids. it’s not him who’s missing the point… Just as confirmed as them being anapsids. Why the hell not? What you are writing looks like "including Ornithischians as Dinosaurs and early Pterosaur like Eodimorphodon as their own clade does not make sense".  source→Synapsids are one clade, Sauropsids are another. That is firstly not relevant and secondly there’s nothing so remarkably reptile-like about them. They are basal Synapsids and hence more reminiscent of the plesiomorphic Amniote condition, but nowhere does that mean that they are reptiles (Some of which simply retained the same condition from their common ancestor). Do you also think there’s no sense in making metatherians a distinct clade, because early metatherians and eutherians were superficially similar? WTF? No. If you call something as long as the entire Cretaceous and Jurassic combined soon… And that’s pretty much the point from where we call them Amniotes. It is presumed that all of them have a common ancestor. Consequently, you can group them into clades. One of them shares a more recent common ancestor with us, the other a more recent common ancestor with the house sparrow. The former is called Synapsida, the latter sauropsida or reptilia. I don’t get the relevance of this, it’s obvious that the two major clades within diapsida had common diapsid ancestors… it seems you are not understanding its relevance. Without accurate terminology, how can you expect to have accurate systematics? No, tetrapods obviously evolved from gnathostomes, not cyclostomata! The ancestors of tetrapods were closer to coelacanths and lungfish (but of course not actually part of either taxon, otherwise we’d be too!). As already stated, that’s a colloquial term and has no longer any relation to phylogenetic nomenclature. It you want to call them fish, then call them that, but don”t expect anyone to give any relevance to it–it has none. True. If you assume that there is a valid clade including the most basal vertebrates and the animals commonly called fish, then that clade includes all vertebrates. But it’s redundant in that case, vertebrata already has a name, it doesn’t need two! The difference is in their phylogeny. Synapsids are the stem group of mammals, reptiles are the stem group of birds, crocodiles, lizards and turtles. That shouldn’t be so difficult to comprehend. It does refute it, that’s a simple fact. A grouping of animals cannot at the same time be a valid clade, and a paraphylum. Then I suggest you read something about them first. By your definition of "reptile", which is just as valid as your definition of "fish"–not at all. Nope, it’s about hard facts, or rather, facts as hard as phylogenetic tree-building software can make it. And this suggests strongly that there is no clade of animals that could be called "fish" or "amphibians" encompassing the animals commonly referred to as "fish" or "amphibians", because these are paraphyletic grades and no natural groups of animals. I suggest you have a closer look at the wiki page you undoubtedly took that term from. "Euryapsids" aren’t valid, and both Ichthyopterygians and Sauropterygians are diapsids, lepidosauromorpha to be exact. In fact they very closely resemble another polyphyletic and quite obviously absurd "class" your logic would justify. No, they aren’t. If evolution was a programming language, the Class-element would be considered deprecated. Classes are nothing but an unrigorous attempt at systematics now replaced by a more objective one. This allows for paraphyla (like amphibia) and potentially also results in polyphyla (like agnatha, or if you were so foolish as to group whales with sirenians and "fish" because they all look superficially similar). That’s why it has been abandoned. Classes don’t "describe" characteristics, they just categorise animals based on more or less proper reasons, potentially grouping animals that are totally unrelated together (euryapsida for example). You seem to believe that your concept of class could exist alongside the concept of a clade, but that isn’t the case. There is the term of a "grade" to describe colloquially known paraphyletic groupings, like "amphibia" for example. But it has no bearing on phylogeny and doesn’t mean these groupings are considered relevant by anyone. Such things as "could be considered" simply have no place in systematics. so in a nutshell, what you were trying to say was simply that you prefer the traditional, outdated meaning of the word? |
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Palaeontologists don’t argue that dinosaurs were not reptiles. In fact, no serious researcher living in the 21st century would do that. It’s now consensually accepted that reptilia should have a monophyletic definition and hence include all its descendants.
