Talk:Dinosaur/Archive 12

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Discussion of diet and digestion?

I'm a bit puzzled as to why there's very little on the extinct dinosars' diet and digestion, whether under a topic of physiology or major divisions between carnivorous and herbivorous exemplars, e.g. Apatosaurus vs. Albertasaurus. I found a nice reference to the herbivorous one being almost certainly hindgut fermenters[1] and I want some place to put it! Monado (talk) 19:17, 22 December 2012 (UTC)

Nice find! I'll see what I can do over the weekend. Petter Bøckman (talk) 00:27, 23 December 2012 (UTC)
Bunch of stuff in the Sauropod Biology volume by Klein et al. 2011 HMallison (talk) 18:24, 31 December 2012 (UTC)

References

  1. ^ Farrow, James O. (1987). "Speculations about the diet and digestive physiology of herbivorous dinosaurs". Palaeobiology. 13 (1). {{cite journal}}: Unknown parameter |season= ignored (|date= suggested) (help)CS1 maint: postscript (link)

Taxobox image

Various dinosaurs incl. Passer
Common specifiers of Dinosauria

I whipped up a revised version of the current taxobox image that's a bit more representative of the six major sub-grups of dinosaurs currently listed (with a 'transitional' feathered theropod for a link with modern birds). What do you guys think? MMartyniuk (talk) 15:00, 28 December 2012 (UTC)

Look good, nice pictures and a good selection of representative lineages! Petter Bøckman (talk) 17:55, 28 December 2012 (UTC)
Nice update. I actually prefer the current picture's Stegosaurus, since the thagomizer isn't cut off. Otherwise, the pictures look really good. You should link the individual uploaders' names, though. Firsfron of Ronchester 18:04, 28 December 2012 (UTC)
Yeah, will do. The issue with the current image is that it seems to have been stretched vertically to forshorten it and include the distal tail! MMartyniuk (talk) 18:31, 28 December 2012 (UTC)
Much better than old one, since theropods aren't overrepresented either. And ouch, the radius and ulna are crossed on that Triceratops... Pronation alert, kill, kill! FunkMonk (talk) 00:41, 29 December 2012 (UTC)
We should really have a Passer in there, given that it's an anchor taxon in most definitions of Dinosauria anyway. Abyssal (talk) 03:14, 29 December 2012 (UTC)

Here are a couple more variations! MMartyniuk (talk) 13:31, 31 December 2012 (UTC)

I like Abyssal's idea of using a Passer in the image; it helps establish the point, visually, that not all dinosaurs are extinct. Firsfron of Ronchester 18:41, 31 December 2012 (UTC)
Neutrality, guys! Let's not get into this whole thing again. For reasons we do not have to waste more server space on, you are not going to get agreement from me or Petter Bøckman for including Passer. As WP:CONSENSUS notes, "a lack of consensus commonly results in retaining the version of the article as it was prior to the proposal or bold edit", and there's nothing significantly "uncommon" here. Ego White Tray's proposal above, Recommend using the lay definition in most dinosaur articles, has failed of consensus, so it will not be implemented, and the same should apply to the collages containing Passer. Petter Bøckman has agreed to File:Various_dinosaurs2.png, as do I, but using Passer instead of Microraptor as the theropod representative is not acceptable. Peter Brown (talk) 21:36, 31 December 2012 (UTC)
I had an idea a while back. Why not create an article called "Mesozoic dinosaur" to specialize in Mesozoic dinosaurs? It should still use a phylogenetic definition, but an article focusing content-wise on the Mesozoic forms sounds perfectly valid. Abyssal (talk) 23:31, 31 December 2012 (UTC)
In the interest of tranquility, how about "Mesozoic Dinosauria", defined phylogenetically? Discuss the Archaeornithes and the Enantiornithes freely, but note that not everyone calls them "dinosaurs". Peter Brown (talk) 00:03, 1 January 2013 (UTC)

I like any of the versions including Passer - There's no neutrality issue here - numerous current reliable secondary sources say that birds are dinosaurs. Excluding Passer for the reason that "birds aren't dinosaurs" gives undue weight to non-technical sources. de Bivort 22:55, 1 January 2013 (UTC)

Sigh. Do we have to rehash this? Numerous current reliable sources, and not just non-technical sources, make statements incompatible with the thesis that birds are dinosaurs. I cite some above, in the third paragraph of Talk:Dinosaur#Conceptual elitism?. de Bivort, cannot you join a consensus that File:Various_dinosaurs2.png is an improvement on the present image, illustrating the six major groups of dinosaurs? No, it does not use Passer as the representative of Theropoda, but it does use Microraptor, which adequately represents the group. If you can bring yourself to concur that it's an improvement, or even to remain neutral on the matter, we need only deal with Firstron's preference for the current Stegosaurus and FunkMonk's problem with Triceratops. Peter Brown (talk) 23:28, 1 January 2013 (UTC)
1) Paragraph 3 does not provide sources saying that "birds are not dinosaurs" which is the only statement that could be given equal weight (as I said). Your inference that the references you provided are consistent with that statement verges on WP:OR. 2) I agree that File:Various_dinosaurs2.png is an improvement. The ones with Passer are more consistent with the sources available to us. 3) Remaining neutral or not is up to me, not you. de Bivort 04:08, 2 January 2013 (UTC)
As we have consensus that File:Various_dinosaurs2.png is an improvement, I have implemented it. The caption needs to to be expanded, identifying the group that each skeleton represents. Further improvements reflecting concerns about Stegosaurus and Triceratops are probably appropriate. As to de Bivort's points:
#1 claims that "birds are not dinosaurs" is "the only statement that could be given equal weight (as I said)," apparently referring to some thesis about "equal weight", but the phrase does not occur elsewhere on this page. In any case, consistency is a logical relation; research as to whether statements are consistent, original or not, is applicable only in mathematical contexts. Peter Brown (talk) 18:05, 2 January 2013 (UTC)
I'm surprised I haven't been clear enough for you yet. This comment was about the overall discussion, and your assertion that a couple sources in third paragraph of Talk:Dinosaur#Conceptual elitism? indicate that birds are not dinosaurs. I have provided numerous sources that say "birds are dinosaurs." You have not provided a single source that says "birds are not dinosaurs." Instead, you have provided sources that you infer to be consistent with that statement. If the goal of this interminable exercise is to determine whether or not reliable sources say that "birds are dinosaurs" or "birds are not dinosaurs," then your evidence is considerably weaker than mine, and deserves less weight in our analysis. I hope that is clearer now. de Bivort 18:44, 2 January 2013 (UTC)
So you are regarding as important whether a source uses the exact words "birds are dinosaurs" or "birds are not dinosaurs"? I haven't checked all your sources, but I don't see the precise phrase "birds are dinosaurs". I thought that your point was that your sources implied that all birds are dinosaurs as, indeed, some of them do. Equally, my sources imply that not all birds are dinosaurs. Surely, implications are more important than exact wording. Peter Brown (talk) 21:27, 2 January 2013 (UTC)
What the - I don't even ... Of course direct quotes are more important than implications, which require inference on your part, and therefore verge on WP:OR. Since you haven't checked my sources, I'll do it for you, using the source numbering from my 1-11 citations above:
  • 1: " fossils are offering a pretty consistent picture that the Birds-Are-Dinosaurs hypothesis is correct"
  • 2: "MODERN BIRDS ARE REALLY BABY DINOSAURS" (that's the title, doesn't require much checking).
  • 3: "When we look at birds, we are actually looking at juvenile dinosaurs"
  • 4: "Birds really are dinosaurs" (subtitle)
  • 5: "the dinosaur suborder that includes Tyrannosaurus rex as well as birds"
  • 6: "Birds are Dinosaurs" (title)
  • 7: "WHY BIRDS ARE BIRDS" (title)
  • 8: "Archaeopteryx is a bird and a dinosaur" (for this one, you'd have to watch the video, which is intended for PreK-1st graders)
  • 9: "birds actually ARE dinosaurs" (first line of text)
  • 10: "The answer is yes: all birds are indeed dinosaurs" (second paragraph)
  • 11: "While the turkey on the table may not seem quite as fierce as the Cretaceous “terrible claw” Deinonychus, they are both feathered dinosaurs" (first paragraph).
Your references offer nothing comparable. de Bivort 22:57, 2 January 2013 (UTC)
Except for the book by Luis Chiappe, a hugely respected paleontologist, my references are all from peer-reviewed journals. None of yours are. Peter Brown (talk) 00:05, 3 January 2013 (UTC)
Because of WP:WPNOTRS (which I assumed you were familiar with) I didn't even look for primary sources. Here are some, all since 2009, all from peer-reviewed journals:
  • 12: "Birds are dinosaurs. That’s hardly the stuff of headlines any more" [1] (secondary).
  • 13: "Anchiornis huxleyi ... a basal avialan filling the morphological gap between non-avian and avian dinosaurs" [2] (primary, prestigious).
  • 14: "The first birds were simply feathered dinosaurs with respect to growth and energetic physiology" [3] (primary).
  • 15: "These results indicate that prior knowledge of the specific taxa can interfere with successful tree thinking. Student's justifications underscore the conflict they had with reasoning with the information that birds are dinosaurs" [4] (primary science education research; relevant?).
  • 16: "Birds are considered dinosaurs that passed the 65 million years ago bottleneck" [5] (primary; bird journal;1st sentence abstract).
  • 18: "Les oiseaux sont des dinosaures" [6] (secondary)
12-18 are the result of a search for the phrase "birds are dinosaurs" in Google Scholar. Here are a portion of the 2009-present results from a search for the phrase "non-avian dinosaurs" (which is still the topic, right??):
That's just from the first page of results, and I'm tired of doing data entry. You cannot deny that both phrases, "birds are dinosaurs" and "non-avian dinosaurs" are abundant in the primary and secondary peer-reviewed literature, as well as secondary sources in the lay press. It's time to consider this thread closed. If you have a specific proposal for changes to the article, present it. Until then, I'm done. de Bivort 02:09, 3 January 2013 (UTC)
Some of those come up with permissions errors when I try to check them. Maybe a browser session thing, or that I'm working from a network with a site license. In either case. They are all but a couple of the links from the first page of the google scholar search for "non-avian dinosaurs" - you can figure out the details if you need to. de Bivort 02:15, 3 January 2013 (UTC)
Cladism is a coherent and respectable philosophical view (see Phylogenetic nomenclature#Philosophy) held by a number of paleontologists. They naturally prefer to consider the dinosaurs as a clade, which requires them to include birds. Their work inevitably dominates in a search for "birds are dinosaurs" (results 12–18). Most paleontologists, however, are focused on their field, not on philosophical matters, and shun the debates, often quite acrimonious, by zealots on both sides. When their technical work leads to hypotheses concerning the entire clade Dinosauria, they regularly add "including birds" in their formulations, realizing that they will otherwise be misunderstood. When these hypotheses do not extend to birds, they will sometimes add the redundant qualifier "non-avian", not so much to be unambiguous (they would be understood anyhow) as to stay well clear of the PhyloCode debates, often quite acrimonious, in which they have no interest in participating. A search for "non-avian dinosaur" will selectively turn these up (results 13–33).
Yes, let us close this thread. If we wish to pursue the discussion elsewhere, I think that primary sources should be the correct focus. Wikipedia policy acknowledges that these are appropriate in some circumstances, and I think that the present matter qualifies. Peter Brown (talk) 14:14, 3 January 2013 (UTC)
I have no desire whatsoever to bandy with you on this topic anywhere else but here (or even here, really, it's just very hard not to take the bait). You talk at length, without supplying the one thing that would settle this debate: numerous, reliable, current, secondary sources that directly support your claim that birds are not dinosaurs. As things stand now, you have dictionaries, and inference from sources that do not directly say what you want them to. With respect to the dictionary sources, WP:UNDUE dictates that we give your position a little bit of weight in the article. Done. 400+ instances of the term "dinosaur" are consistent with your view point. With respect to the primary literature and your inferences, this is exactly why using primary sources to make a point is discouraged. The fourth example at WP:SYNTH is precisely what you are doing. Taking a source, and then inferring a step beyond what the authors actually wrote. Inadmissible. de Bivort 17:36, 3 January 2013 (UTC)
Perhaps my sources to date don't clearly imply that Passer is not a dinosaur, though. A source that does so is Wang et al. (2005), which implies both in the title and in places in the text that dinosaurs are extinct; it follows that Passer is not a dinosaur. Also, Passer is a bird, and the text contains the sentence, "As dinosaur has been considered as the ancestor of modern birds and the CvP-bias of dinosaur is likely similar to those of birds," which clearly considers birds to be a group separate from dinosaurs. Peter Brown (talk) 21:27, 2 January 2013 (UTC)
See reply below, under the citation. de Bivort 23:06, 2 January 2013 (UTC)
#2 overlooks the fact that consistency is all or none. The only way A can be more consistent than B is for A to be consistent while B is inconsistent. In the present case, File:Various_dinosaurs2.png is consistent with the sources, since every skeleton depicted is that of a dinosaur. Nothing can be "more consistent". Peter Brown (talk) 18:05, 2 January 2013 (UTC)
Incorrect. Articles, arguments, source etc. say more than one thing. A proposal can be consistent with none, some or all of the aspects of a source. This file is consistent with some of aspects of the sources, but fewer aspects than the images with Passer. I hope that is clearer now. de Bivort 18:44, 2 January 2013 (UTC)
File:Various_dinosaurs2.png is fully consistent with every statement (= "aspect"?) of every source that either one of us has provided. One can't do much better than that. Since the proposition implicit in the image, that all six skeletons are from dinosaurs, is true, these statements had better be consistent with it; any statement inconsistent with a true proposition is false. Peter Brown (talk) 21:27, 2 January 2013 (UTC)
It is not consistent with the aspect/statement that modern birds are dinosaurs. This is an important concept (lots of notable, reliable, secondary sources state it explicitly), and in my opinion deserves representation in the taxobox image. de Bivort 22:59, 2 January 2013 (UTC)
The image makes no representation about modern taxa and does not need to. Martin Martyniuk does not share your opinion as to what your concept "deserves"; see below. In my opinion, he makes good sense. Peter Brown (talk) 00:05, 3 January 2013 (UTC)
Martin Martyniuk can probably answer for himself, but I would guess he would prefer an image with Passer if it weren't for this interminable kerfuffle. Firs and Abyssal would prefer a version with a bird. But, we needn't beat this particular dead equine any further, you and I are both fine with the current image. Off to go find primary literature for you (for the other dead horse). de Bivort 01:19, 3 January 2013 (UTC)
Martin Martyniuk would probably point out that he's actually named Matthew Martyniuk. :) Firsfron of Ronchester 04:05, 3 January 2013 (UTC)
Ha, serves me right for copy-paste. de Bivort 04:24, 3 January 2013 (UTC)
Thanks for moving the discussion back here. I can't keep track of it when it moves to multiple pages. Firsfron of Ronchester 05:10, 3 January 2013 (UTC)
Speak of the devil and he appears. I'm trying to stay out of this short of voting, but if you want my opinion, certain editors seem miffed that "cladists" want to tear down Linneaus' nice neat boxes which many non-cladists still enjoy using. The fact is that in my experience, 99.99% of dinosaur paleontologists are "cladists". So the discussion should center on whether the article named "Dinosaur" should follow the majority opinion of dinosaur paleontologists, or paleontology as a whole, which may be two different things. I say this article should obviously follow the consensus of the field it covers, whether or not the philosophy of that field differs from the philosophy of related fields when it comes to taxonomy and nomenclature. If that means this article says Passer is a dinosaur and the Passer article says it's not a dinosaur citing some Linneanist neontologist, so what? That's just a reflection of current reality. I'm agnostic as to which ends up in the taxobox, as long as the article makes it absolutely clear that all relevant scientists consider birds to be just as much a subgroup of dinosaurs as sauropods. MMartyniuk (talk) 20:00, 3 January 2013 (UTC)
#3 is wholly obscure. Why should there be an asymmetry in the matter of neutrality? Peter Brown (talk) 18:05, 2 January 2013 (UTC)
You asked me to "bring myself to ... remain neutral" on the topic of the images, presumably because you don't like that Passer should be included and I was arguing in favor of that. I found this presumptuous and was pointing out that I am within my editorial rights to comment on whatever discussions I choose. de Bivort 18:44, 2 January 2013 (UTC)
I said, "If you can bring yourself to concur that [File:Various_dinosaurs2.png is] an improvement, or even to remain neutral on the matter. . ." The clause was hypothetical, not a request. In the event, you did concur. If there really was an implict request, you obliged. This was most constructive, as it confirmed the existence of consensus. Peter Brown (talk) 21:27, 2 January 2013 (UTC)

Reference

  • Wang, GZ; Ma, BG; Yang, Y; Zhang, HY (2005). "Unexpected amino acid composition of modern Reptilia and its implications in molecular mechanisms of dinosaur extinction". Biochemical and Biophysical Research Communications. 333 (4): 1047–49. doi:10.1016/j.bbrc.2005.05.039. {{cite journal}}: Cite has empty unknown parameter: |author-name-separator= (help); Invalid |ref=harv (help); Unknown parameter |author-separator= ignored (help)
I'm not sure what to make of this article. It's not published in a paleontological journal and says in the abstract "modern Reptilia, the sibling of dinosaur [sic]." Reptilia is a paraphyletic group containing dinosaurs. They may simply be confused on the taxonomy. Moreover, in all instances the article refers to "dinosaur extinction" rather than the extinction of all dinosaurs. Obviously dinosaurs underwent a massive extinction, (the topic of the article) - but nothing they write is inconsistent with some dinosaurs surviving that extinction. And even if it were, they have lost taxonomic credibility with that odd statement in the abstract. de Bivort 23:06, 2 January 2013 (UTC)
You're right, "dinosaur extinction" might refer only to the extinction of many dinosaurs. I have cited other work, however. I particularly like the source entitled "The first hatchling dinosaur reported from the eastern United States" but it didn't seem appropriate to cite it in connection with a bird like Passer that was not indigenous to North America. Peter Brown (talk) 00:05, 3 January 2013 (UTC)

I can't decide which I find more depressing, the argued implication in the year 2013 that Passer is not a dinosaur or the argued implication in the year 2013 that Microraptor is not a bird while Archaeopteryx is! ;) That said, the reason I initially included M. is that in general, taxobox images represent more basal members of a clade, so that you can visually see the evolution of a group as you click through the subgroup links. Maybe we should just slap an Eoraptor in there and call it a day. Anyway, using Microraptor visually shows the reader the link between birds and dinosaurs rather than simply including a modern specifier, which may be initially baffling and off-putitng for some who don't bother to carefully read the text. I had wanted to use the Berlin Archaeopteryx for this reason as it's far more iconic, but it didn't really fit the orientation unless I flipped it horizontally, which seemed wrong for some reason. MMartyniuk (talk) 21:58, 2 January 2013 (UTC)

On flipped Archaeopteryx, take a look at this: http://commons.wikimedia.org/w/index.php?title=File:EB1911_-_Volume_02.djvu&page=376 FunkMonk (talk) 11:38, 3 January 2013 (UTC)
I would just offer my support for Peter Brown's attempt to curb the frontloading of phylogenetic taxonomy going on here. The picture with Microraptor is perfectly acceptable from both a phylogenetic standpoint, the only reason I can see for insisting on one with Passer is to emphasize phylogenetic nomenclature. The solution MMartyniuk suggested above has the benefit of catering to both sides as well as following the general Wikipedia trend. I do not intend to stay and argue my case here though, life's too short to end up like this. Petter Bøckman (talk) 11:27, 3 January 2013 (UTC)
ha! ... sort of. de Bivort 17:39, 3 January 2013 (UTC)

Must-read for the BANDits here

http://www.quackwatch.com/01QuackeryRelatedTopics/pseudo.html I recommend that three certain editors read this linked article and ask themselves if they really wish to waste everybody's time any further. You're smart and knowledgeable, please help instead of obstruct. HMallison (talk) 14:02, 3 January 2013 (UTC)

It is very difficult to attribute to any of the editors on this page any of the characteristics of the "pseudoscientists" condemned here. de Bivort did cite "literature aimed at the general public", The Guardian for example, but Wikipedia standardly considers reputable newspapers to be reliable sources. Peter Brown (talk) 14:35, 3 January 2013 (UTC)
Good Grief! Bandits, pseudoscience? Seriously? Petter Bøckman (talk) 16:32, 3 January 2013 (UTC)
BANDits are indeed psuedoscientists, as they employ every logical fallacy in the book, most notably moving the goalposts (er, ah, dromaeosaurs are birds now, so there!), straw man (BAD is wrong because birds evolved from arboreal animals and no dinosaurs were arboreal!), and no true Scotsman (an arboreal dinosaur you say? hogwash--if it's arboreal, it's a bird, as no true dinosaur lived in trees). However, the implication that the people posting here are pseudoscientists is wrong, because taxonomy is not objective and is therefore not a science. Whether or not we call Microraptor a bird or a dinosaur has no basis in objective fact. It's a label. MMartyniuk (talk) 20:05, 3 January 2013 (UTC)
That's the problem, though: they're not really BANDits. The BANDits claim that birds are not dinosaurs in any sense, that birds derived from some other, unspecified amniote group. Peter, Petter, and Ego admit that birds are dinosaurs in the cladistic sense, but cite shaky sources (online dictionaries, coloring books, a single press release) to state that birds are descended from dinosaurs, but cannot be dinosaurs, because dinosaurs are extinct. At no point have they cited BANDit papers. The literature they've cited is not even close to BANDit research. In fact, they appear to be unaware of the BANDits, which by 2013 is a WP:FRINGE idea.
I also disagree that the three editors are obstructing anything. It's just a discussion, and people can feel free to take part or not. Their comments are meant in good faith, and if the worst that happens because of this debate is that we don't have a picture of a living bird in this article, it won't be too terrible. I liked Abyssal's suggestion (still do), but I won't press it too hard because any of the new pictures would be okay scientifically, as we'd expect from pictures compiled by Martin...er, Matt. ;) Firsfron of Ronchester 18:10, 3 January 2013 (UTC)
Thank you guys putting me on the tracks to clarifying what a BANDit is supposed to mean. I thought it referred to some WP.policy, and tried every permutation of the word with no result. I was a bit puzzled, because I believe Mallison has called me that before, and I could not for the life of me fathom why he would accuse me of earning my living as a criminal (I don't even have a parking ticket on my record). I an quite familiar with Fediccia & Co though. Their opposition did actually bring one good thing in starting the investigation that eventually lead to the discovery of the frameshift of finger developement. I just never had heard them called BANDits before.
As for the colouring book, I cited it only to counter you argument that feathers and small wings on dinosaurs close to birds were somehow discovered around 2006 and this prompted the change of wording. The colouring book mas merely an example of this being known back in 2002, as in "even this childrens colouring book got that right in 2002". I never forwarded it as scientific literature. Neither did any of us "admit" birds evolved from dinosaurs, that point was never in dispute. The actual phylogeny is possibly the only thing we ever agreed fully on here. It is a bit hard to discuss thing when the opposition do not care to actually read your argument.
In a related note, I guess MMartyniuk was implying the Xu & al. paper above. This is an interesting paper, but I haven't followed the field closely enough to know if this analysis is now conventional wisdom. Didn't Lee & Worthy (2011) claim Xu & al was wrong? If we for the sake of the argument assume Xu's right, I can only see two possible scenarios: 1) flight evolved once, and Troodontidae and Dromeosauridae are both secondarily flightless (I suppose this is the "modified birds-came-first stance"?) or 2) flight evolved twice, and Archaeopteryx was a "para-bird". If I read Xu right, nr 2 is his position. It's however neither mentioned here or in Evolution of birds, and only implicitly in Archaeopteryx. As an ecologist I find this scenario extremely interesting. Shouldn't something about this be added? Petter Bøckman (talk) 21:54, 3 January 2013 (UTC)
I disagree with with Xu et al's analysis and I think the problems with it have been pointed out by Lee and worthy as well as others online. current consensus of data is that Archie is slightly closer to modern birds than Microraptor. I was referring to gross morphological similarity. Both have fully-formed wings and may or may not have been capable of powered flight. Any reasonable Linneaan classification would place these in the same "order" if not "family" and certainly not different "classes". The only reason Microraptor is considered a 'dinosaur' rather than a 'bird' is the vagaries of arbitrary cladistic definitions, so it baffles me why people who complain about phylo-loading these articles are alright with letting the cladists determine what is or isn't bird, a line which even I think is currently at the most ridiculously arbitrary and illogical point possible! The article Bird states in the first line of the introduction that birds are "are feathered, winged, bipedal, endothermic (warm-blooded), egg-laying, vertebrate animals." Based on current knowledge, this definition applies to all maniraptoriform 'dinosaurs' at least including ornithomimosaurs, oviraptorosaurs, and deinonychosaurs.
To turn this into something other than a rant, I'd be curious to see you and Peter Brown state what you think is a dinosaur and what is a bird, and why. It's apparently ok to include Microraptor but not Passer. Ok, what about Archaeopteryx? Jeholornis? Confuciusornis? Hesperornis? We're obviously going to need some ground rules here or at least be able to understand where each side is coming from to start to resolve this. MMartyniuk (talk) 13:50, 5 January 2013 (UTC)
Which archosaurs were birds and which were not isn't one of the points at issue. Many articles, this one for example, call Microraptor a dinosaur and do not call it a bird; we are simply basing our preferred terminology on this literature. You seem to be proposing to do away entirely with Aves as a taxon; perhaps that is a good idea, but it is hardly a common one in the field. Peter Brown (talk) 15:52, 5 January 2013 (UTC)
I must admit I am not intimately familiar wit the detail at the bottom of the avian tree. Like Peter B. and yourself pointed out, I've never seen Microraptor being called anything other than a dinosaur, and I was under the impression it was a glider only, so I assumed it belonged somewhere further down the tree than Archy. It appears I'm not the only one. Microraptor frequently figure on "smallest dinosaur" lists. Either that honour goes to Compsognathus, or one has to include birds and ad a humming-bird. Even if one stick to "Mesozoic dinosaurs", some of the enanornithes were sparrow-sized, so it seems it's a widespread misunderstanding.
As for what makes a bird, I'm fairly certain flapping has something to do with it. The general consensus seems to be Archy had some limited powered flight abilities or at least "flapping assisted gliding". Gliders are dime a dozen in this world, birds are true fliers. So: Flapping things with feathers = bird, non-flapping things with or without feathers =/= not bird. Of course, in Linnaean taxonomy you will have these critters that falls right at the divide (the transitionals), the things that adds spice to life (and any text dealing with evolution). Petter Bøckman (talk) 22:18, 5 January 2013 (UTC)
But doesn't this definition illustrate the flaw at the heart of Linnean taxonomy - "if it doesn't flap, it's not a bird." What about ratites, penguins? As soon as you (sensibly) extend the definition to "flappers plus their descendants", then you have laid the (cladistic) groundwork for birds being classified as dinosaurs, no? de Bivort 04:09, 6 January 2013 (UTC)
For the record, the pectoral anatomy of Microraptor and Archaeopteryx are very similar, and that of Microraptor is actually more advanced in some ways (Microraptor had a fused, ossified sternum while Archaeopteryx did not; Microaptor had an alula-like structure on the first wing digit while this has not been reported for Archaeopteryx). The common belief that Archaeopteryx had limited flapping and that Microraptor was strictly a glider is demonstrably false. It is currently debatable whether either could flap, but whatever aerial capability Archaeopteryx had (if any), Microraptor also must have had. MMartyniuk (talk) 17:02, 10 January 2013 (UTC)
I can't see any flaw here, unless one insist on a purely phylogenetic approach. Since the world is (and presumably was) full of vertebrate gliders, then I hope we can agree that powered flight really made a difference, and put birds on an evolutionary course very different from their relatives? It's no more problematic to say birds are not dinosaurs that to say you and I are are not fish. Both the ecological shifts in question (land-air, water-land) represent major transitions with enormous consequences for anatomy and ecology and to me make sensible goalposts for classes. Of course, today our knowledge is so great the shifts are known almost down to species level. Then again, we usually have no problem accepting grades at the species level, so I see no problem in continuing this approach upwards. Petter Bøckman (talk) 08:14, 6 January 2013 (UTC)
I'm sorry, but I don't follow at all. Should I conclude that you don't in fact think that ratites and penguins are birds? de Bivort 14:46, 6 January 2013 (UTC)
No, they are birds, just like snakes are tetrapods, despite lacking legs. Come one, it's not like you don't know the normal Linnaean classification scheme, is it? Petter Bøckman (talk) 15:00, 6 January 2013 (UTC)
Perhaps I don't, but I was just going off of your line that "non-flapping things with or without feathers =/= not bird" de Bivort 17:12, 6 January 2013 (UTC)
You don't? Aren't you a biologist working with fruit-flies? Well, the Linnaean system works in the sensible way you suggested five posts up. Just to be snarky, I'd like to point out that both penguins and ratites do actually flap their wings now and then, they just don't fly with them.Petter Bøckman (talk) 19:26, 6 January 2013 (UTC)
Linnean taxonomy was never taught as anything other than a historical referent in my undergrad or grad training. I think you're referring to evolutionary taxonomy which permits paraphyletic groups. The sensible definition I gave above, an organism plus its descendants, is precisely a cladistic, rather than [13] definition. I just want to double check: If we were to define dinosaurs as something like "an Eoraptor-like archosaur with characters X Y and Z, and all its descendants" you'd agree that it would include birds, right? de Bivort 21:37, 6 January 2013 (UTC)
Sorry, I mixed up the two, traditional taxonomy often goes by the name "Linnaean taxonomy". You are of course right. As for your example, whether your dinosaurs would include birds depends on what X, Y and Z are. If e.g. Z is "non-volant", then birds fall outside. All this is quibbling though. Birds are a very derived group with a quite limited anatomical range (due to flying), had you put up all dinosaur (clade) species that ever lived side by side, the birds would still stick out like a sore thumb. A few, like Microraptor would be sort of in between, but that is how it is with transitional fossils. The reason traditional taxonomy is how it is (with warts and grades and all) is that its primary purpose is to be a practical way of squaring animals away. One of the most important traits is stability, and birds were a separate class to begin with. As many of the PhyloCode proponents has argued, had we stated all over, things would (I'd say might) look different, but we are not starting all over.
Er, I think whatever characters you use to define the eoraptor-like beast that is the ancestor of both Triceratops and Tyrannosaurus (even if one of them is "non-volant"), then the group defined as "said beast and all descendants of it" includes birds. de Bivort 23:08, 6 January 2013 (UTC)
I work in an educational institution, and one of my tasks is to keep track of all animal groups, even jellyfish, sipunculids, hemichordates and earthworms, not just vertebrates. I need a good filing system and a way to express things to the lay public. I have little use for a taxonomy grouping crocodiles with birds and not with lizards. When I finally come to the point where I do present surviving archosaurs, it is only after about an hour of touring school kids in dinosaur anatomy and habits and the origin of birds. Petter Bøckman (talk) 22:55, 6 January 2013 (UTC)
I can sympathize with the challenge of portraying all of this to the lay public as coherently as possible. But, I would personally use the filing system that evolution has provided for us. de Bivort 23:08, 6 January 2013 (UTC)

I agree. i have read a paper about how birds are apparently not dinosaurs that was written by a BANDit and to tell the truth it was not very good. the writer despite being a "Professional Ornithologist" seemed to lack basic knowledge of bird anatomy, as what he calls a bird's knees are actually a it's ankles. and the said that Theropod dinosaurs use their thighs even though the majority of them didn't (only Oviraptorosaurs did). that's pretty embarassing already but second he did not provide an alternative for what birds might have evolved from and the entire paper devolved into the author patronizing and insulting the intelligence of the reader. BANDits should not be considered professional Ornithologists as they seem to lack essential knowledge of birds. and they should definetly not be considered scientists as they do not utilize ths scientific method. their logic is also very flawed, according to them every feathered dinosaur is actually a bird which if that is true, it means Yutyrannus and Concavenator are birds, which makes no sense. and they extend it to that every feathered dinosaur should be classified under at least Avialae, which makes no sense because what will happen if we discover a feathered sauropod?--50.195.51.9 (talk) 16:51, 9 January 2013 (UTC)

Yes, there is some pretty awful stuff out there. I don't see that a detailed critique of such trash advances the discussion here, however. Petter Bøckman, with vast experience in the matter, thinks that the cause of educating the public is better served by grouping crocodiles with lizards than by grouping them with birds. From my very limited training and experience as a volunteer guide at the Harvard Museum of Natural History, I see no reason to question his opinion. If you have some expertise in educating the public in zoology, you are certainly welcome to share it, since this is something that Wikipedia is trying to do. Peter Brown (talk) 18:08, 9 January 2013 (UTC)
But why should we group Crocodylians with Squamates? If the goal is to educate the public, wouldn't it be counterproductive to state that Crocodylians are lizards? Currently Crocodylians are not considered lizards (Assuming the definition of "lizard" is belonging to the Squamata) and are instead considered Archosaurs. 50.195.51.9 (talk) 12:59, 10 January 2013 (UTC)

Less technical introduction?

Perhaps the best way to satisfy laypeople whose eyes glaze over when they find little in the article of what they expected would be a generally accessible, less technical introduction, comparable to Introduction to evolution. In that article, simplified trees could be shown which give an overview and contrast the current technical definition with lay concepts of "dinosaurs". It can provide lists of highly recognisable species that laypeople tend to be most interested in, links to non-dinosaur sauropsids that are typically discussed in the same context in popular accounts (Dimetrodon, pterosaurs, ichthyosaurs, plesiosaurs, mosasaurs) so that people will not be confused at their absence but educated about the taxonomy, discussion of records such as largest and smallest, etc. I realise that a lot of this has already been incorporated into the article, but perhaps it is still a bit too much buried there for the general reader. Evaluating feedback from outsiders, whether personally prompted or collected automatically, should provide useful indications if the needs of the readers are met. (Strangely, I can't find the link to the feedback section on this talk page.) Unfortunately, I can't be of much help with this, being a layman myself, however, even if one who is (I'd think) much more comfortable with highly technical articles than the average reader. --Florian Blaschke (talk) 01:02, 5 January 2013 (UTC)

Hi Florian!
The feedback section for this article is at the very bottom of Dinosaur, under the navigation templates. I agree that a simplified tree diagram could help the article. The General description portion of the article does try to point out that many "pop culture" 'dinosaurs', like the ones you mention, are not dinosaurs. Perhaps this fact could be re-added to the lead of the article (it used to be there). Firsfron of Ronchester 01:26, 5 January 2013 (UTC)
Sorry for being unclear, I meant the subpage where comments from readers are collected and can be inspected by editors. I have found links to such subpages on other talk pages, somewhere in the templates on the top, but not here.
I do suspect that lay readers would like to find links to popular real dinosaur genera and species such as Tyrannosaurus rex, Triceratops, Iguanodon, Stegosaurus, Apatosaurus, Diplodocus or Velociraptor in the article, too, not only mention of the "pseudo-dinosaurs". It might be difficult to find a source for such a "top 10 most popular dinosaurs list", though. It may also seem unencyclopedic, but the high profile of these dinosaur genera and species can be ascertained objectively, in principle. Admittedly, I can't think of a good way to incorporate such a list that wouldn't have the experts objecting. --Florian Blaschke (talk) 01:43, 5 January 2013 (UTC)
I suppose a bubble diagram of reptiles down to order level with silhouettes of typical representatives would help, something like this, only with less fish and more detailed amniotes. Do you think this would help, Florian? Petter Bøckman (talk) 08:37, 6 January 2013 (UTC)
That sounds like a good idea! However, in practical implementation, it should also be quite ambitious. Could this possibly remain manageable? I'm not quite sure what exactly you have in mind. I would really like to see an attempt. I think you would need two diagrams, one to show the place of the dinosaurs and the various other -saurs within the amniotes, and one to show the place of several representative genera within the dinosaurs. --Florian Blaschke (talk) 21:49, 12 January 2013 (UTC)

range includes birds

I just wanted to say that I think this is a good addition. de Bivort 02:12, 25 January 2013 (UTC)

Yes, the range includes birds, sauropods, and guaibasaurids, among many other groups which were not originally considered dinosaurs. Weird how we're constantly discovering new things ;) MMartyniuk (talk) 12:40, 25 January 2013 (UTC)

Regarding Zhou 2004

These edits are a bit bewildering. I'd say that if you're going to remove a cite, either remove the pertinent reference completely or find another place where it is pertinent as a cite. As it is Zhou 2004 under the Further Reading heading is the odd man out: a review article among mostly popular and semi-technical books. As for the pertinence of the removal of the cite I'd point out the use of "non-avian dinosaur" in the paper:

Until now, no enantiornithine has been reported from the Cenozoic: thus it is likely that this group of early birds became extinct at the end of the Mesozoic together with non-avian dinosaurs.

The elongated prezygopophyses and chevrons of the caudal vertebrae bear a close resemblance to those of dromaeosaurs, confirming a close link between birds and this lineage of non-avian theropod dinosaurs.

With 10 other mentions to go with those above quoted. Now it is peculiar that "feathered dinosaur" is used as well, though it can be argued that the removal of "non-avian" from the expression is to avoid being repetitive. Besides what else would you call a dinosaur that was found with feathers and doesn't have the skeletal hallmarks of a bird? Feathered dinosaur is the minimum I'd say. Dracontes (talk) 10:37, 18 February 2013 (UTC)

Well, I don't think it an objection that Zhou 2004 is the "odd man out". The world could use a few more odd men.
As regards pertinence: Zhou 2004 is cited to back up the claim that birds "are considered a subgroup of dinosaurs in most modern classification systems". Yet Zhou identifies only a single source to the effect that birds are dinosaurs, a 2002 paper by Prum. This is wholly inadequate as support for a claim about "most modern classification systems".
Peter Brown (talk) 04:47, 19 February 2013 (UTC)

Edit request on 17 April 2013

Please add the following paragraph to the "Size" section of the "Biology" part of the article: The Expanding/Growing Earth Hypothesis regarding the evolution of the Earth itself suggests there was less gravity on Earth when dinosaurs roamed it, which would explain why the largest dinosaurs evolved to be so massive. Neal Adams demonstrates the Expanding Earth Hypothesis with some compelling evidence here: http://www.youtube.com/watch?v=oJfBSc6e7QQ Exmodione (talk) 07:54, 17 April 2013 (UTC)

Sorry, but we don't need fringe material sourced to a you-tube video, fails WP:RS. Vsmith (talk) 09:59, 17 April 2013 (UTC)

Failure to adapt to changing conditions

Interesting hypothesis, the old classic one. But if birds are dinosaurs, then dinosaurs are today still the most specious group of all tetrapods - a wonder of adaption and variety, the greatest comeback before Lazarus. Failure to adapt new conditions? Ridiculous. --W-j-s (talk) 23:53, 9 February 2013 (UTC)

Well, all but one dinosaur lineage went extinct at the K-P boundary, so in the majority of cases, they failed to adapt, yeah. de Bivort 03:30, 10 February 2013 (UTC)
Technically, that's debatable. Though rumor has it some of this may be challenged in upcoming papers, but based on current understanding of Cretaceous avialan diversity, there seem to have been at least five or six lineages of Avemetatarsalia that crossed the K-Pg boundary. Most of them just happen to be members of Aves, though it's possible that at least one non-avian avialan lineage got through, represented by Qinornis. As mentioned, it is possible that some Cretaceous "avians" aren't really avian at all, and that crown-group Aves didn't originate until the Paleogene, but that would be quite a trick given the presence of undisputed paleognaths and anseriformes very early in the Paleogene. MMartyniuk (talk) 15:14, 24 February 2013 (UTC)
It's a matter of choice whether one calls several Avemetatarsalia lineages "several lineages" or "one lineage" - but that said, measured just as biodiversity / # species - the majority of dinosaurs went extinct at the boundary, no? Or was the majority of dinosaur diversity pre-meteor birdlike? de Bivort 15:31, 24 February 2013 (UTC)
This is an active area of controversy/research. One reason why the "Toroceratops" thing is so prominent is because it has huge implications for the pre-K-Pg diversity of non-avialan avemetatarsalians. If you lump Torosaurus and Nedoceratops into Triceratops, lump all Maastrichtian pahycephalosaurs into P. wyomingensis, lump all NA Maast. duckbills into E. annectens, lump Nanotyrannus into T. rex, etc., suddnely non-avialan dinosaurs look like the vast minority of dinosaurs compared to Maastrichtian bird lineages. There are Maastrichtian non-avialan dino faunas in other parts of the world besides NA like Madagascar and the Shantungosaurus fauna of Asia, but their proximity to the K-Pg boundary isn't secure AFAIK. Then there's the late Maastrichtian fauna of Antarctica which so far seems to be exclusively avian. MMartyniuk (talk) 18:57, 24 February 2013 (UTC)
What's your intuition about error bars on these estimates? I assume there were far far more than few dozen dinosaur species, and that we know about only this many for sampling reasons. Is there likely to be a sampling bias, or do you think that the avian/non-avian ratio (once lumping is resolved) will likely extend to all species world wide? What about the other reasonable metric: number of individuals. Were the avian species as abundant as non-avian species? de Bivort 14:58, 25 February 2013 (UTC)
Worldwide, it's probably a sampling thing. In fact if I had to put money on true Paleogene non-avialan dinosaurs, it would be in the Danian of Antarctica ;) However, North America is pretty thoroughly sampled, and though many species are known from scraps, I think we have a pretty good idea of diversity. MMartyniuk (talk) 22:12, 25 February 2013 (UTC)
So, how about abundance? No. of avian vs non-avian individuals? de Bivort 01:44, 26 February 2013 (UTC)
If you want to call it a "lack of adaptation" that a catastrophic event, which previously had never exerted evolutionary pressure, wiped them out. HMallison (talk) 12:01, 10 February 2013 (UTC)
@Debivort: That's the point: toothless dinosaurs survived the impact and after that, their ability to adapt to the new conditions was very successful. The classic hypothesis says, that even before the impact the dinosaurs failed to adapt to changing conditions, e.g. in the flora. This means, that there must have been a fundamental difference between feathered dinosuars with teeths and those without. I cannot see this. So I conclude, that the only reason for the extinction of nearly all dinosaurs was the impact. --W-j-s (talk) 12:49, 24 February 2013 (UTC)
Interesting, but for editing purposes it's OR unless you can cite authors to support that. There's the problem of dividing the Theropoda into avian and non-avian. To some extent the division is quite arbitrary and gives rise to some very pedantic argument re the survival of the Dinosauria beyond the KT. Also I don't think there's much dispute that the dinosaurs were declining before the impact event. A number of avians did not survive the Cretaceous, as did numbers of the groups that persisted in to the Cenozoic,ie., crocodiles, turles, mammals and many of the invertebrates. The Cretaceous was an indiscriminate killer, and why some survived and others did not is still a mystery.Gazzster (talk) 20:38, 25 February 2013 (UTC)
Not much dispute that dinosaurs were declining before the impact event? Check out, e.g., Lloyd et al. (2008). Peter Brown (talk) 23:36, 25 February 2013 (UTC)
@Gazzter: As Peter M. Brown said, there is much dispute about the hypothesis of declining dinosaurs before the K-T-event. Because as birds have to be regarded as dinosaurs they proof that dinosaurs had the ability to adapt very well. Birds - and this means also theropod dinosaurs - are today the most specious group of all tetrapods, they outnumber the mammal species more than twice. And because birds are very similar to other maniraptora it is simply not plausible, that the other maniraptora did not had this ability of adaption, either. In fact, there is more and more evidence, that only a few groups of dinosaurs declined while others florished until the impact. And this is not a surprise. In the last 65 million years one can sea a decline of some groups of mammals, too, while others began grew.
In fact, there is now much more evidence, that the impact killed nearly all animal species larger than 20 kg and especially most warm blooded species. New interpretations of fossils show, that the adaptive radiation of the mammals started after the K-T-event and not - as molecular genetics suggested - millions of years before. This means, that perhaps only a handful placentalia species and only a handful species of birds survived the impact.
Cold blooded species on the other hand could much easier survive a long cold and dark period with very rare food, so it is not suprising, that much more species of crocodiles, turtles, amphibia or insects survived the impact.
btw, as I am not a native English speakers my ability to edit and correct the article is very limited. But I think, it's not OR to point on the fact, that that hypothesis of declining dinosaurs does not fit with the success and variety of today's birds. --W-j-s (talk) 20:28, 27 February 2013 (UTC)
This is all very interesting, but what do we want to change in the article? I would however point out the dangers inherent in the syllogism you seem to be relying upon: 'birds adapt superbly to changing environments. Birds are dinosaurs. Therefore dinosaurs adapted superbly to changing conditions'. The first premise needs qualification. So does the second. Birds may be dinosaurs (though it is still not a scientific dogma mind you, though a number of editors assumes it is) but not all dinosaurs are birds. Consequently the conclusion needs to be qualified.Gazzster (talk) 02:08, 4 March 2013 (UTC)
This is not my argumentation. I just say, if birds are dinosaurs, they proved, that some - not all - dinosaurs had the ability to adapt very well. The thesis critisized by me is, that the dinosaurs became extinct because they failed to adapt long before the K-T-event. Birds - if they are dinosaurs - show that this is wrong. So the new formulated thesis must be: some dinosaurs failed long before the K-T-event to adapt to new conditions, while some have been very sucessful (and maybe not only toothless birds with pygostyl). But if some species of a clade became extinct, while their relatives are successful, that's just life: By numbers of species hominidae failed to adapt, too. As fossile records show, there have been much more species of Hominidae some 20 million years ago than today. And by number of specimen, all species of hominidae together have less then 200.000 individuals, while other apes have far more. So hominidae have failed like the dinosaurs. To be correct: non-human hominidae, because I've excluded 7 billion individuals of homo sapiens when talking about hominidae. --W-j-s (talk) 17:42, 8 March 2013 (UTC)
I understand your reasoning -thanks for clarifying - but what does it mean to say that some dinosaurs had the ability to adapt better than others? Did they possess some mysterious quality or organ (as do birds apparently according to your theory) that allowed them to evolve faster than other creatures? Or were they so 'generalised' in structure as to be able to survive in varying environments? The dinosaurs of the Late Cretaceous were, if anything, more specialised than many of their predecessors. Dinosaurs were 'failing' to adapt to new conditions, and being replaced, throughout the Mesozoic! Gazzster (talk) 06:54, 20 April 2013 (UTC)
I don't think that there is a mystery, why some species adapt better than others, even their relatives. One should expect that in a normal distribution. The article suggests, that the dinosaurs were on a declining paths and the impact (and/or the vulcanoes in India) were only the last nail in the çoffin. Birds (and other maniraptorians) show, that the thesis of a decline of all dinosaurs is wrong. And I don't suggest, that some birds survived because of some mysterious quality or organ. There is no evidence for something like this. This means birds in the creteceous have been just a normal clade of maniraptorian dinosaurs with a normal ability to adapt to new conditions. Only a few specialised birds survived the K-T-event, and I don't think, it was because of their "adaptiveness", I think it was just luck. The surviving birds showed indeed a fantastic ability to adapt to new conditions, but there is no reason to assume, that other dinosaurs, if they had survived, too, wouldn't have shown a similiar ability. --W-j-s (talk) 22:11, 25 April 2013 (UTC)

Effect of variation in gravitational field strength?

Many questions may be answered in the following talk (in italian language) added under "Dinosauria" in the vikipedia italian site:
Ipotesi "gravitazionale" sulla scomparsa dei dinosauri. Ho costruito questa ipotesi partendo dalla seguente considerazione: nel periodo dei dinosauri, il Mesozoico, esistevano grandi vertebrati massicci in grado di volare, ed alcuni carnivori, come il Tyrannosaurus Rex, dotati di una grande agilità, necessaria per la predazione, nonostante la loro considerevole massa (fino a 100 tonn.). Questa circostanza potrebbe essere spiegata da un più basso valore, a quell'epoca, della gravità sulla superficie della Terra, vale a dire (a parità di massa) da un diametro maggiore della sfera terrestre. La Terra si sarebbe evoluta dimensionalmente, un po come le stelle, rimpicciolendosi gradatamente per effetto della Gravità, sempre vincente sulla pressione interna del nucleo, in via di raffreddamento. Lo scenario quindi potrebbe essere stato molto diverso, nel Mesozoico, da quello che solitamente immaginiamo: non animali mastodontici che si muovono lentamente nel nostro mondo, come vediamo nei film fantastici, ma, riproporzionando, agili e veloci predatori in un mondo abbastanza più grande di quello attuale. La progressiva diminuzione del diametro terrestre, con il conseguente aumento del valore di "g" sulla superficie, spiegherebbe l'evoluzione morfologica dei dinosauri: da rettili bipedi in origine a quadrupedi poi, forma questa più adatta al sostegno di un corpo massiccio. La necessità di adattamento al crescente aumento della gravità superficiale terrestre, potrebbe aver causato, in alcuni vertebrati, un progressivo alleggerimento delle ossa che, unito ad altre mutazioni, avrebbe dato origine al passaggio evolutivo dai dinosauri agli uccelli. Tuttavia, negli animali più massicci, tale evoluzione adattativa non sarebbe stata abbastanza efficace, per cui la struttura ossea di questi, esposta ad un graduale collasso, sarebbe infine risultata insufficiente al suo scopo vitale causando così la "grande estinzione del Cretaceo". Ancora Luciano - 13:01, 24 apr 2013 — Preceding unsigned comment added by 79.55.252.35 (talk)
E' un modello interessante ma non spiega come mai assieme ai dinosauri siano scomparsi anche organismi di piccole dimensioni come ammoniti, belemniti, rudiste e perfino foraminiferi microscopici.--l'etrusco (msg) 13:13, 24 apr 2013 (CEST)
La mia ipotesi non è esclusiva, ma potrebbe essere vista come fattore "concomitante" alla scomparsa dei dinosauri. La causa finale, o "colpo di grazia", resterebbe quella dell'"impatto meteorico" che avrebbe causato, contemporaneamente, l'estinzione di altre forme di vita: ammoniti, mosasauri, plesiosauri, pterosauri, ecc. L'ipotesi gravitazionale risponderebbe altresi a quesiti, ancora irrisolti, sugli insuccessi/successi evolutivi di adattamento, da parte di specie diverse, avvenuti prima dell'evento catastrofico, cioè: il lento declino dei dinosauri massicci e la loro fine improvvisa, contro il successo evolutivo che permise la sopravvivenza all'impatto di alcune specie di dinosauri "pennuti e con denti": i futuri uccelli. Ancora Luciano - 11:10, 26 apr 2013 — Preceding unsigned comment added by 79.55.252.35 (talk)

The hypothesis that the earth's diameter increased until some time in the Mesozoic and later contracted, with resulting effects on the force of gravity at the earth's surface, has no support from reliable sources. Owen (1976), p. 230, has proposed a constant increase in diameter from the Cryogenian to the present, but with no reversal in the Mesozoic; Cox (1990) has extensively reviewed this proposal and several similar ones, but no one has apparently suggested a contraction. The suggestion by 79.55.252.35 appears to be pure OR. Peter Brown (talk) 16:56, 26 April 2013 (UTC)

References

  • Owen, H. G. (1976). "Continental Displacement and Expansion of the Earth during the Mesozoic and Cenozoic". Philosophical Transactions of the Royal Society of London. Series A. 281 (1303): 223–291. {{cite journal}}: Invalid |ref=harv (help)
  • Cox, C. Barry (1990). "New Geological Theories and Old Biogeographical Problems". Journal of Biogeography. 17 (2): 117–130. {{cite journal}}: Invalid |ref=harv (help)
[Da Vikipedia (in italiano), alla voce "Espansione della terra"]: La teoria dell'espansione, formulata per tentare di spiegare la posizione e il movimento dei continenti sulla superficie della Terra, non trova riscontro nella scienza moderna, costituì fonte di polemiche e fu superata dalla teoria della tettonica a placche. La teoria tocca paradigmi fisici profondamente radicati. Le teorie fisiche moderne, come la relatività, suppongono che lo spazio esterno sia vuoto (non c'è etere) e che la Terra resti un punto molto isolato nello spazio, rotolando lungo la curvatura dello spazio-tempo causata dal Sole. Inoltre, la teoria dell'espansione contraddice i principi della meccanica celeste, poiché se la terra fosse in crescita la sua orbita sarebbe progressivamente alterata fino al punto di precipitare sul Sole, visto che la forza centrifuga non sarebbe più sufficiente a compensare la forza di gravità. Quindi, se la Terra non si è espansa, deve essersi contratta, giustificando così il più basso valore di "g" nel Mesozoico, che è alla base della mia ipotesi. Ancora Luciano — Preceding unsigned comment added by 79.35.252.234 (talk) 11:03, 27 April 2013 (UTC)
As Newton demonstrated, it is only the the mass of a spherical body that figures in celestial mechanics; its diameter is irrelevant. He deferred the publication of Philosophiæ Naturalis Principia Mathematica until he had established that point. Expansion and contraction have no effect on the orbit; so long as the earth's mass and its distance from the sun remain constant, there is no change in the force exerted on the earth by the sun's gravitational field.
The graph on p. 230 of the Owen paper cited above clearly indicates a continuing expansion of the earth's diameter throughout the Paleozoic and Mesozoic. The Cox paper disputes this, arguing that there was no significant change in diameter during this period. To set yourself against these two sources, arguing for a contraction, you need to provide a reliable source yourself.
The article it:Espansione_della_Terra is tagged ricerca originale, "Original research". Reference to it is not appropriate until this matter is resolved. In particular, the article makes use of the mistaken celestial mechanics you have repeated here. Peter Brown (talk) 15:29, 27 April 2013 (UTC)
OFF-TOPIC POST HIDDEN — REVERT ONLY IF PROVIDING WELL-SOURCED MATERIAL RELEVANT TO THE K–Pg EXTINCTION
Ammettiamo che vi sia stata un'espansione della Terra (a massa costante) e quindi una diminuzione di "g" sulla superficie terrestre, rispetto al suo valore nel Mesozoico. Allora: sarebbe possibile oggi ricostruire idealmente, sui reperti fossili più imponenti finora trovati, animali in grado di muoversi oggi ancora più agevolmente che all'epoca della loro esistenza, quando "g" era più grande???. Secondo me alcune teorie andrebbero rivisitate, tenendo in opportuna considerazione la Gravità, che è la forza della natura che, oltre a generare i "buchi neri", potrebbe alla fine aver ragione di tutto, riducendo l'intero universo alle dimensioni di un punto. — Preceding unsigned comment added by Ancora Luciano (talk • contribs) 04:52, 29 April 2013 (UTC)

Peter Brown (talk) 16:20, 29 April 2013 (UTC)

Edit request on 12 February 2013

Your article says the following: "Although the word dinosaur means "terrible lizard", the name is somewhat misleading, as dinosaurs are not lizards. Rather, they represent a separate group of reptiles with a distinct upright posture not found in lizards, and many extinct forms did not exhibit traditional reptilian characteristics."

If dinosaurs do not exhibit reptilian characteristics, how can you say they are a "separate group of reptiles"? Dinosaurs were not and are not reptiles. The sentence should be changed to: 'a separate group' and the 'of reptiles' should be removed.

Thanks,

Anthony Anthony_Mendoza (talk) 06:38, 12 February 2013 (UTC)


Dinosaurs are definitely reptiles. Abyssal (talk) 11:37, 12 February 2013 (UTC)
This of course depends on how you define reptile. If dinosaurs are reptiles, so are birds. Most people don't have a problem with this, some do. On the other hand, the sentence is wrong wither way. If something is a reptilian characteristic, it must be shared with most or all reptiles. If a characteristic is not common to all reptiles, it is therefore not a reptilian characteristic. I'd agree the statement should be removed unless examples of these supposed characteristics (diapsid skulls? scales? hard-shelled eggs?) are given and sourced. The statement seems to oversimplify the difference between lizards and other reptiles to the point that it's useless and misleading as currently listed. MMartyniuk (talk) 12:26, 12 February 2013 (UTC)
I think that the operative word here is "traditional". As such scaled, cold-blooded and crawling is probably what the text Anthony quoted is getting at. As for actual sauropsid synapomorphies, if the counterpoint should be needed, this seems to be a good start. Dracontes (talk) 21:03, 17 February 2013 (UTC)
Just drop the second of the two sentences, which contributes nothing. No need to get into phylogeny at this point. Saying that dinosaurs are a separate group just repeats the statement in the first sentence that dinosaurs are not lizards. "Traditional reptilian characteristics" is hopelessly vague. Peter Brown (talk) 21:39, 17 February 2013 (UTC)
Or we could cite a relatively consensual semi-technical source for what is traditionally reptilian and how dinosaurs differ from that. The new edition of Grzimek's Animal Life Encyclopedia seems a good one from the skim I gave to the intro on the reptile volume. Fair enough regarding such an early introduction of taxonomy and the two phrases could be subsumed into one.

Although the word dinosaur means "terrible lizard", the name is somewhat misleading, as dinosaurs are not lizards, representing instead a separate group of reptiles which, like many extinct forms, did not exhibit characteristics had as traditionally reptilian, such as a sprawling limb posture or ectothermy.

Tangentially I'm not entirely sure what you understand as "upright posture". While many dinosaurs could certainly splay their limbs to some extent especially the basal ones such as Saturnalia and Guaibasaurus their usual locomotory posture was erect (Fechner 2009, pp. 64-69). Dracontes (talk) 09:37, 18 February 2013 (UTC)
Or even better:

Although the word dinosaur means "terrible lizard", the name is somewhat misleading, as dinosaurs are not lizards, representing instead a separate group of reptiles which, like many extinct forms, did not exhibit characteristics historically had as reptilian, such as a sprawling limb posture or ectothermy, due to their limited extant diversity.

Dracontes (talk) 09:42, 18 February 2013 (UTC)
In writing that "Many sauropods and ornithischians did not have an upright posture" I took "upright posture" as meaning that the animal stood up on its hind legs. That was careless of me; I should have realized that a parasagittal stance was meant. It is evident here, however, that someone has deleted the sentence. Perhaps the editor was trying to do me a favor by deleting an unconstructive comment, but such deletion is inappropriate unless it is covered in Wikipedia:Talk page guidelines#Others' comments. The editor will please refrain from doing this again. Peter Brown (talk) 04:28, 19 February 2013 (UTC)
I would also be careful in excluding ectothermy from a definition. Endothermy has not been proven in every dinosaur, and there remains a case for ectothermy in a number of genera.Gazzster (talk) 02:12, 4 March 2013 (UTC)
bring it, then! I, for one, know of not a single dinosaur that still can reasonably be considered distinct from all others, and the evidence for homoiothermy and endothermy is overwhelming. HMallison (talk) 22:47, 11 March 2013 (UTC)
Then you might consider the problem of massive dinosaurs like the sauropods. There are too problems with endothermic sauropods: first, finding enough food to maintain a constant body temperature, especially considering the size of their jaws; and second, the problem of the dinosaur overheating. These difficulties have been noted enough times. The evidence for endothermy is strongly suggestive, at least for some dinosaurs, but not conclusive.Gazzster (talk) 07:01, 20 April 2013 (UTC)
It would be nice if HMallison would produce a reliable source to the effect that "the evidence for homoiothermy and endothermy is overwhelming." Also, why does Gazzster caution against excluding ectothermy from a definition of "dinosaur"? The characteristic would be useless for the purpose unless all or nearly all dinosaurs were ectothermic, and that is certainly not the current scientific consensus. Analogously, one must exclude the presence of a carina from a definition of "bird", since a significant minority of birds lack one. Peter Brown (talk) 14:59, 20 April 2013 (UTC)
Not an analogous argument. Modern birds possessed carina ancestrally which were secondarily lost in some lineages. This would be like excluding limbs from the definition of tetrapod due to the existence of snakes. Unless you're using bird in the broad sense. Either way, talking about ectothermy and endothermy as a dichotomy is inaccurate. Most sources suggest non-avian dinosaurs (including powered flying non-avian dinosaurs like enantiornithes) were somewhere in between croc-like ectothermy and bird-like endothermy based on growth rates. MMartyniuk (talk) 15:31, 20 April 2013 (UTC)
Granted; while possession of a carina cannnot be taken as a necessary condition of an animal's being a bird, which is what I had in mind, a definition of "bird" could use carinae in the way indicated. Is Gazzster proposing, though, that considerations of dinosaur metabolism somehow be incorporated in the article's definition of Dinosauria? Right now, the competing definitions in the first three paragraphs of Dinosaur#Definition are wholly phylogenetic. I can't see how adding matters of thermoregulation would be an improvement. Peter Brown (talk) 16:55, 20 April 2013 (UTC)
I was only suggesting that dinosaurs should not be defined as endotherms.A few possibly were, and many probably did have metabolisms something like endothermy. But the few can't define the all. I suppose if dinosaurs are defined as reoriles some reference to metabolism might be made.Gazzster (talk) 22:21, 20 April 2013 (UTC)
Not done: please establish a consensus for this alteration before using the {{edit semi-protected}} template.  TOW  talk  18:54, 21 February 2013 (UTC)

Birds and dinosaurs are reptiles.

Birds should be classified as reptiles if dinosaurs are too. --209.188.40.63 (talk) 21:36, 29 April 2013 (UTC)

I second this, People are too hesitant to admit that Birds are reptiles.--65.96.242.22 (talk) 19:05, 30 April 2013 (UTC)
But dinosaurs aren't classified as reptiles...Farsight001 (talk) 19:25, 30 April 2013 (UTC)
Not so classified by whom? In 1842/3 Richard Owen defined Dinosauria as "a distinct tribe or suborder of Saurian Reptiles". Peter Brown (talk) 19:45, 30 April 2013 (UTC)
Dinosaurs are indeed classified as reptiles. Birds are dinosaurs. However, birds are not classified as reptiles. Similarly, synapsids are reptiles, and mammals are synapsids, but mammals are not classified as reptiles. It's because reptiles are a paraphyletic group. It really doesn't make much sense. I don't consider it proper, but that's just the way it is. Ferocious Flying Ferrets 19:46, 30 April 2013 (UTC)
If all As are Bs and all Bs are Cs, then all As are Cs. There are various ways of sorting out the terminology, but let's not defy the rules of logic. Peter Brown (talk) 19:56, 30 April 2013 (UTC)
It should be that simple, but it isn't. Ferocious Flying Ferrets 20:06, 30 April 2013 (UTC)
I guess science is finally realising how arbitary and artificial the Linnaean system is. In fact any system is artificial insofar as it is an attempt to impose order on nature for the sake of human understanding. So based on shared characteristics a bird could be a dinosaur. Heck, one could even make a case for classifying Diplodocus as a bird, or even a mammal, on the basis of shared characteristics. It all depends upon what set of characteristics scientists are going to agree on. However, for the sake of a wiki encyclopedia it's problematic to start calling birds reptiles. I do see the logic though.Gazzster (talk) 01:15, 1 May 2013 (UTC)
These are deep questions. Gazzster seems to adopt something like Protagoras' dictum that man is the measure of all things, that objectivity is nothing but intersubjectivity. The contrary view is Plato's, that nature should be carved at the joints, which presupposes that there are joints, distinctions between natural kinds or something like that. It is difficult to explain the progress of science unless Plato's view is roughly correct. Diplodicus distinguished from Aves only because humans like to think of them as different? Paleontology, it seems, would then be an idle pursuit. Peter Brown (talk) 02:07, 1 May 2013 (UTC)
What do the sources say? de Bivort 03:51, 1 May 2013 (UTC)
Reptiles#Phylogenetics and modern definition. Many contemporary researchers agree with the initial statement: birds are indeed reptiles in a phylogenetic sense. The traditional definition has lost importance and is increasingly seen as an artifact of history, much like former conceptions that would treat whales as fish (but not land mammals, which we now realise ultimately descend from fish, too) and even much stranger early classifications, compare Kingdom (biology)#Summary. --Florian Blaschke (talk) 21:18, 1 May 2013 (UTC)
The distinction between birds and reptiles has lost no importance except in academic disputations. No zoo includes birds in a "reptile house". Kingdom (biology)#Summary is irrelevant. Peter Brown (talk) 22:42, 1 May 2013 (UTC)
It's not a zoo, but the AMNH is in fact organized this way. [14]. de Bivort 00:19, 2 May 2013 (UTC)
Perhaps the distinction has lost importance in some public exhibits, but it is quite robust in others. In the National Zoo in Washington, D.C., the walk from the reptiles to the birds is not short. Overall, has the distinction lost importance? To argue so, I expect, would be quite difficult. Peter Brown (talk) 02:40, 2 May 2013 (UTC)
Then again, the prairie dogs aren't housed in the small mammal house, even though they are small mammals. We can count ourselves lucky that what matters for the article is what reliable secondary and tertiary sources say, rather than how zoos and museums are organized. de Bivort 05:05, 2 May 2013 (UTC)
Quite so. What is a reliable source for the thesis that the traditional definition has lost importance and is increasingly seen as an artifact of history? There certainly is contemporary work, in Palaeos for example, that makes the distinction quite unapologetically. Peter Brown (talk) 16:51, 2 May 2013 (UTC)
It feels like you're trying to broaden the argument. I'm just saying that to resolve this "birds and dinosaurs as reptiles" section, we should appeal to sources herpetological, ornithological and paleontological. There's no point in arguing without sources. de Bivort 17:13, 2 May 2013 (UTC)
Agreed, arguing without sources is pointless. Accordingly, I'm requesting a source for a very specific point: that "the traditional definition" is increasingly seen as an artifact of history. I don't see how that broadens the argument. If Petter Bøckman is correct, below, that we will have to live with the relevant terminological diversity for decades, then the traditional distinction will not be seen as "an artifact of history" for some time. Of course, if you can rebut his thesis with a reliable source, that will be a different matter. Peter Brown (talk) 19:02, 2 May 2013 (UTC)
Well, that's on Florian, not me. I was just trying to bring the focus back in this discussion. That said, I don't think a reference is need that says that per se. Those are your goalposts. What is needed are (current, reliable, secondary, etc) references that either say "birds are reptiles" or "birds aren't reptiles." I have nowhere near the passion for this point as I did for the BAD / BAND question, so I'll leave it to others to hit up google scholar. de Bivort 22:26, 2 May 2013 (UTC)
Snyspida is not a reptiles in any sense, since it appeared before reptiles. I don't think synspdida is in repiles, but they are in amoate.
Also, birds are underneath reptiles. I think this is non-standard and unneacpetlbe to exclude birds just because they are warm blooded. --209.188.46.176 (talk) 22:25, 1 May 2013 (UTC)
I would have ignored this as nonsense. Petter Bøckman, a more patient and considerate editor than I, has graciously responded to your concern at Talk:Synapsid#Class or subclass?. Engage him there, if you think you really have a point, rather than cluttering up various talk pages. Peter Brown (talk) 22:42, 1 May 2013 (UTC)

Hardly Peter ;-) The basic problem is of course that taxonomy is trying to cater to two aims these days: The original aim of ordering and the post-Darwinian aim of reflecting phylogeny. There are ways of letting the two live side by side on one system (Evolutionary taxonomy), but the proponents of phylogenetic nomenclature are these days pressing for a purely phylogenetic approach, at the expense of ordering. The problem of course is that we need both a handy way of classifying animals and a system of reflecting phylogeny without drawing trees all the time. I suspect this is a situation we will have to live with for decades, until either a) classification and phylogeny part ways or b) taxonomy are replaced by a new system. Only time will tell. Petter Bøckman (talk) 13:33, 2 May 2013 (UTC)

An interesting and well-argued discussion. So I take it there is no consensus for referring Aves as a sub-classification of Reptilia?Gazzster (talk) 01:08, 3 May 2013 (UTC)

Physiology

Please link "air sacs" to Bird_anatomy#Respiratory_system. 96.61.88.217 (talk) 07:23, 13 May 2013 (UTC)

Section on inclusion/exclusion of birds

Peter M. Brown, is this section really necessary? I feel this is covered adequately in Definition. Also, it seems that you are confusing use of "dinosaur" as a vernacular or colloquial term with support for a formal paraphyletic group. When a paper title includes the word "fish", it does not necessarily follow that the authors of that paper implicitly support the use of a paraphyletic taxon Pisces. MMartyniuk (talk) 17:23, 23 June 2013 (UTC)

The full title of the paper I cite is, "The first hatchling dinosaur reported from the eastern United States: Propanoplosaurus marylandicus (Dinosauria: Ankylosauria) from the Early Cretaceous of Maryland, U.S.A." Neither "dinosaur" nor "Dinosauria", in context, is a vernacular or colloquial use. Peter Brown (talk) 17:53, 23 June 2013 (UTC)
If you honestly believe Weishampel, at least (one of the co-authors) advocates for a paraphyletic Dinosauria, I suggest you read any of his books. "Hatchling dinosaur" here is clearly being used colloquially. At the very least, there is no possible way you can seriously argue this kind of usage is a tacit, professional advocation of a paraphyletic taxon excluding birds. MMartyniuk (talk) 20:30, 23 June 2013 (UTC)

My addition of a new section to the article has been rejected as "synthesis". The only argument for birds' being dinosaurs that I know about, however, is that birds are descended from dinosaurs, and I can produce sources presenting that as the reason. If there is another reason, it needs to be included in the article. Descent works as a reason only if paraphyletic taxa are rejected, however, and such rejection is a controversial matter, much too controversial for Wikipedia to takes sides on. Peter Brown (talk) 17:39, 23 June 2013 (UTC)

And so we need a disclaimer on every single biology article? I don't think so. This should be discussed on Phylogenetic taxonomy etc., not Dinosaur. Or Mammal. Frankly, the opinion that paraphyletic groups are ok is a minority in dinosaur science and should be treated with the same amount of space as the BAND hypothesis (i.e., one or two lines, not an entire sub-header). Yes, paraphyletic groups are advocated by workers in other fields, but dinosaur paleontology is nearly 100% in favor of clades nowadays. Suggesting or implying otherwise is dishonest. Rejection of paraphyly may be controversial in general, but this is not a general article on the philosophy of biological classification. MMartyniuk (talk) 20:26, 23 June 2013 (UTC)
OK, I'll compose the one or two lines. Maybe a few more. Peter Brown (talk) 21:56, 23 June 2013 (UTC)
Just to add, I don't see what the point is of writing in these kinds of disclaimers and contrarianism. Like BANDits, opponents of cladistics and PN have not proposed any decent alternatives. If I were to decide to follow a paraphyletic concept of Dinosauria, how exactly would that work? What is the alternate definition or diagnosis of Dinosauria vs birds (Aves, or Avialae, btw?)? Is Microraptor a dinosaur or not and why? What about Aurornis? Archaeopteryx? Is Aves the crown, the branch, the Archaeopteryx node, or something else? These questions all have practical problems for Wikipedia (what date goes in the Bird taxobox for their origin, for example?) Until such things are worked out by supporters of paraphyly and validly published on by numerous researchers and a consensus is reached, all of this anti-monophyly stuff is extremely counter-productive. MMartyniuk (talk) 20:37, 23 June 2013 (UTC)
Here I disagree. Pointing out difficulties with the dominant paradigm is an essential part of the endeavor. Were it not for papers like James & Pourtless (2009), there would reason to fear that the birds-from-dinosaurs theory was not being adequately challenged. Alternative theories are not necessary at all stages; only when the network of auxiliary assumptions needed to support the dominant theory becomes unwieldy is a new paradigm required. Peter Brown (talk) 21:56, 23 June 2013 (UTC)

Reference

  • James, Francis C.; Pourtless, John A., IV (2009). "Cladistics and the Origin of Birds: A Review and Two New Analyses". Ornithological Monographs. 66: 1–78. {{cite journal}}: Invalid |ref=harv (help)CS1 maint: multiple names: authors list (link)
What difficulties? This boils down to a pure matter of opinion--whether or not to recognize paraphyletic groups. I'm pointing out that people who choose to recognize paraphyletic groups stop there. They recognize them, and then do zero work to actually create a workable alternative framework. At this stage it appears to be pure contrarianism, not an alternative classification system. The last person to actually propose an alternative framework was Benton in 2004, nearly a decade ago, which was inadequate at the time and has only gotten worse with age, as it leaves out numerous major taxa and has not been updated to reflect changes in our understanding of dinosaur relationships. Livesy and Zusi attempted to do the same for early birds in 2007, but their arrangement of taxa and the incompleteness of their included early bird taxon sample was so out of synch with actual science that it's never been viewed as anything but complete joke by dinosaur paleontologists familiar with this area. (Full disclosure, I discussed this issue in more depth in my book and even offered an improved framework for the Linneaan classification of dino/birds, but I'm loathe to add my own material and would not personally advocate that this should be used in place of phylogenetic nomenclature, which is the near-universal lingua franca of this subject area.) MMartyniuk (talk) 11:28, 24 June 2013 (UTC)
You mentioned BANDits; my comment was to defend their brief inclusion. James & Pourtless claim that the statistics supporting the accepted phylogeny are flawed. If so, that's a difficulty. If not, it merits rebuttal. Peter Brown (talk) 14:22, 24 June 2013 (UTC)
Unfortunately, there is no formally published rebuttal to that (objectively terribly done) study, but there are plenty of rebuttals online, e.g. [15]. Comments in this blog post [16] suggest critical reviewers may have been ignored. Agree that somebody should put this in print. Ignoring dissenting opinions to push a pre-concieved agenda based on horribly out of date concept of the subject area. Once again, BANDits show themselves to be the equivalent of creationists. MMartyniuk (talk) 21:04, 25 June 2013 (UTC)
For comments on the problems with this particular study (such as assuming, rather than testing, that Longisquama is an archosaur) see also the comment of Andrea Cau (one of the authors of description of Aurornis). As he notes, an earlier phylogenetic study specifically designed to test alternative suggested placements of birds with Amniota and including more taxa than the study of James and Pourtless, i.e. Philip Senter's dissertation (which James and Pourtless do not cite and might have not been aware of) does support placement of birds within Theropoda. --Macrochelys (talk) 18:34, 26 June 2013 (UTC)
There is a short refutation of the paper in: Dyke, Gareth and Kaiser, Gary (eds.) (2011) Living dinosaurs: the evolutionary history of modern birds, Chichester, GB, Wiley, 440 pp. The most embarrassing aspect of this publication (James & Pourtless (2009), that is :o) is that it shows precisely the opposite of what the authors thought it did: even after manipulating the data to about the maximum that the cladistic method allows, they still couldn't find a clear alternative candidate for the rôle of bird ancestor. So it functions as a test of the standard phylogeny, which is hereby strongly corroborated.--MWAK (talk) 17:27, 2 September 2013 (UTC)

Age of dinosaurs

This page mentions that dinosaurs are 150 million (or somewhere around there) years old, which I disagree with. How can you tell how old the dinosaur is? --Dianasweetiegina (talk) 04:10, 24 June 2013 (UTC)Dianasweetiegina

150 million years old? Not close; have you even read the page? We can "tell" by reading reliable sources, which are provided abundantly. Peter Brown (talk) 14:13, 24 June 2013 (UTC)

Scientists have been able to determine beyond reasonable doubt that dinosaurs are between 230 and 66 million years old using various methods for dating the age of geological formations, most of which are generally very reliable. --24.36.130.109 (talk) 01:51, 8 July 2013 (UTC)


Nesbitt's unambiguous synapomorphies

In the Distinguishing anatomical features section, the text reads "...S. Nesbitt confirmed or found the following 12 unambiguous synapomorphies, some previously known:". By my count, only 11 bullet points follow. Somehow one was either lost, never added during the original edit, or the count is simply wrong.

Good point. The twelfth point has now been added.--MWAK (talk) 16:13, 2 September 2013 (UTC)
Twelve seems like an implausibly large number of synapomorphies for any group, the dinosaurs in this case. I infer from the Synapomorphy article that a synapomorphy, by definition, is present in the last common ancestor of a group but absent in its immediate ancestor. That would mean, would it not, that the twelve traits jumped aboard all at once in a single speciation event? This does not accord with the gradual nature of evolution that I thought was the dominant view. The synapomorphies can be grouped, somewhat, cutting down on the total number; the two listed items relating to the fourth trochanter of the femur can surely be combined into one. We are left, however with changes to the skull roof, the cervical vertebrae, the limb bones, and the pelvis, all of which happened at once according to Nesbitt. Can a case can be made out that these are interdependent; that no one change could have occurred without all the others if the animal was to remain functional? If not, the proposition that all twelve traits are synapomorphies of the dinosaurs is difficult to accept. Peter Brown (talk) 23:19, 2 September 2013 (UTC)
If any group has a large number of synapomorphies, doesn't that just mean there's a relatively large gap between it and more basal groups? That is, we would expect the number of synapomorphies to drop steadily as we find more near-dinosaurs. MMartyniuk (talk) 21:15, 3 September 2013 (UTC)
Exactly. However, this also means that those near-dinosaurs were the first species showing the apomorphies and thus are implicitly referred to by the original larger list of synapomorphies. Also, those apomorphies might first have been acquired by very basal dinosaurs, although this requires a degree of parallel evolution. The synapomorphies were in such cases not changes in the real last common ancestor but in a range of species. It is this range that is represented by the larger list.--MWAK (talk) 09:09, 4 September 2013 (UTC)
Well, these traits would not have to be acquired all at once. Indeed, at the moment of speciation, e.g. by allopatry, the last common ancestor of dinosaurs might well have been morphologically indistinguishable from its ancestor. During the, perhaps many, million years of its subsequent existence — of course the "ancestor" is now seen as an ancestral species, not a single individual — new traits could gradually have evolved. However, it is indeed quite implausible (though not impossible) that the actual last common ancestor of the Dinosauria really was the species showing for the first time these twelve innovations. The high number in all probability indicates a serious gap in the fossil record. You see, in cladistics, the "last common ancestor", when related to a set of synapomorphies is always a methodological fiction. It might truly have been a single species but more often will have been a group. The data — the actually discovered extinct and extant species — do not allow us to resolve this group and therefore we treat it as if it were one species. One has to keep this in mind :o).
By the way, in general traits should only be combined if there is a material implication.--MWAK (talk) 06:50, 3 September 2013 (UTC)
So a last common ancestor is usually not a species but a species group? And what species are in the group depends on what, in our present state of knowledge, we are able to resolve? "Synapomorphy" is defined in terms of LCA, so this would mean that what traits are synapomorphies is also relative to our state of knowledge. If we called something a synapomorphy last year but refuse to call it one this year, apparently we need not have changed our minds; due to new discoveries and enhanced technology, the scope of the term can change from year to year so that a 2012 synapomorphy need not be a 2013 one. Is this made clear anywhere in Wikipedia? For starters, Last common ancestor#MRCA of different species and Synapomorphy are seriously in need of updating.
In the Erythrosuchus article, it is stated,
The hypothetical last common ancestor of archosaurs is thought to have shared many features with Erythrosuchus, many of which are found in the braincase.
Is the "last common ancestor" in this context a species group? Does calling it "hypothetical" mean that no fossil in any of the group members has been found? Or is it a particular species, and the implication of "hypothetical" is that we have no fossils in that species?
Similar questions arise for a huge number of articles. Peter Brown (talk) 15:59, 3 September 2013 (UTC)
"So a last common ancestor is usually not a species but a species group? " I guess that depends on how you define "species", but I think it would be better to think of the LCA as a population. When two populations within a species become isolates, they remain the same species for quite a while under most species concepts before speciation occurs. MMartyniuk (talk) 21:17, 3 September 2013 (UTC)
The term "group" isn't mine; I'm trying to understand MWAK's statement
You see, in cladistics, the "last common ancestor", when related to a set of synapomorphies is always a methodological fiction. It might truly have been a single species but more often will have been a group. The data — the actually discovered extinct and extant species — do not allow us to resolve this group and therefore we treat it as if it were one species.
You prefer populations as ancestors, which is in better accord with the Phylocode than MWAK's groups. Do you agree with MWAK that LCA is "a methodological fiction"? Peter Brown (talk) 21:40, 3 September 2013 (UTC)
"Do you agree with MWAK that LCA is "a methodological fiction"" It depends on the context. Certainly, any two given eukayotic organisms had a singe LCA that was a real genetic population of organisms. My understanding, which could be wrong, is that not only is the actual LCA incredibly unlikely to be preserved in the fossil record due to its incompleteness, but that even if this ancestor does indeed exist in a form that can be coded, cladistic methodology will recover it as a basal sister group rather than as an ancestral node. LCAs exist, but cladistic methodology alone cannot tell us what they are without extra interpretation of the data. For example, it is possible that the population of ceratopsids that contains the type specimen of Rubeosaurus is directly ancestral of the population that contains the type specimen of Einiosaurus, which in turn may be ancestral to the clade Pachyrostra in an anagenic lineage. Nevertheless, cladistic analyses usually recover the former two specimens as successive outgroups to pachyrhinosaurs, which is not inconsistent with the hypothesis that this is a single lineage--it's just an artifact of how cladistic analyses work. In the above example, the last common ancestor of Rubeosaurus ovatus + Pachyrhinosaurus canadensis (=clade Pachyrhinosaurini) would be Rubeosaurus ovatus itself. But because phylogenetics does not allow for paraphyletic taxa, this can't be expressed directly, though we must realistically acknowledge that all species evolved from some other species, and thus most species are paraphyletic in one way or another. MMartyniuk (talk) 10:58, 5 September 2013 (UTC)
MWAK carefully distinguishes the "actual last common ancestor", a real population or whatever, from "the last common ancestor when related to a set of synapomorphies" which is always a methodological fiction. Do you agree that there is an important distinction here? I don't think that coding an ancestral group as a basal sister is really "fictional", since it represents a hypothesis that is correct for all we know. Peter Brown (talk) 17:13, 5 September 2013 (UTC)
Well, a "last common ancestor" to which synapomorphies are attributed in a cladistic analysis will usually be a species group. The actual last common ancestor is by definition a species or a certain set of individuals (depending on the definition).
Indeed, what we know to have been the synapomorphies, is dependent on our present state of knowledge. As our knowledge increases, the number of synapomorphies will eventually decrease and the number of species factually included in the species group will decline, approaching the one species that is the actual last common ancestor. That actual last common ancestor is referred to in a clade definition; such a definition does not indicate a species group.
The sentence "The hypothetical last common ancestor of archosaurs is thought to have shared many features with Erythrosuchus..." confuses the actual last common ancestor ("the hypothetical last common ancestor of archosaurs" — it is both actual and hypothetical, i.e. not known to have been found yet) with the fictional last common ancestor (the species group sharing those synapomorphies with Erythrosuchus). The fact that we are unable to resolve a group does not necessarily mean we haven't found any fossils of these species, just that we as yet don't know this.--MWAK (talk) 09:09, 4 September 2013 (UTC)
You write of "what we know to have been the synapomorphies". Based on the following sentence, I think you mean "what are the synapomorphies." The phrase "have been" refers to an indefinite time in the past and, as you say, the set of synapomorphies varies with the state of knowledge. Prior to 1842, there were no dinosaur synapomorphies because the dinosaur-concept hadn't even been formulated.
Such details aside, I find your POV quite convincing. Is it OR or can you provide sources so that these ideas can be incorporated in Wikipedia articles?
Peter Brown (talk) 16:52, 4 September 2013 (UTC)
Ah, I fear in many matters I'm rather a Realist :o). Certainly I do not see the synapomorphies as merely (I would say, being a Realist) a social construct.
"Hidden species" are a well-known problem in the phylogenetic species concept. Our discussion is perhaps simply about the relation between the phylogenetic species concept and the biological species concept. An elegant solution was offered by this article: Pleijel F. and Rouse G.W., 2000, "Least-inclusive Taxonomic Unit: A New Taxonomic Concept for Biology", Proceedings of the Royal Society of London – Series B: Biological Sciences 267: 627–630. The LCA is then in cladistic analyses a LITU, without any claims about it being a species. In most Wikipedia articles it is unnecessary to reveal such implicit problems.--MWAK (talk) 07:01, 5 September 2013 (UTC)
I'll take a look at the paper. You have written:
"in cladistics, the 'last common ancestor', when related to a set of synapomorphies is always a methodological fiction."
Are the synapomorphies themselves methodological fictions even though they're not social constructs? Since synapomorphies are generally defined in terms of LCAs, I would expect them to be no less fictional. Peter Brown (talk) 17:38, 5 September 2013 (UTC)
The traits as such are to be considered real; their combination in a set of synapomorphies is in cladistics a methodological fiction: you pretend that there is a single species for the first time showing certain modifications, while it is likely these modifications were acquired by a range of species. However, a degree of fictionality has always been overt, as such a set clearly functions as an hypothesis.--MWAK (talk) 08:22, 6 September 2013 (UTC)

Age of dinosaurs

This page mentions that dinosaurs are 150 million (or somewhere around there) years old, which I disagree with. How can you tell how old the dinosaur is? --Dianasweetiegina (talk) 04:10, 24 June 2013 (UTC)Dianasweetiegina

150 million years old? Not close; have you even read the page? We can "tell" by reading reliable sources, which are provided abundantly. Peter Brown (talk) 14:13, 24 June 2013 (UTC)

Scientists have been able to determine beyond reasonable doubt that dinosaurs are between 230 and 66 million years old using various methods for dating the age of geological formations, most of which are generally very reliable. --24.36.130.109 (talk) 01:51, 8 July 2013 (UTC)


Nesbitt's unambiguous synapomorphies

In the Distinguishing anatomical features section, the text reads "...S. Nesbitt confirmed or found the following 12 unambiguous synapomorphies, some previously known:". By my count, only 11 bullet points follow. Somehow one was either lost, never added during the original edit, or the count is simply wrong.

Good point. The twelfth point has now been added.--MWAK (talk) 16:13, 2 September 2013 (UTC)
Twelve seems like an implausibly large number of synapomorphies for any group, the dinosaurs in this case. I infer from the Synapomorphy article that a synapomorphy, by definition, is present in the last common ancestor of a group but absent in its immediate ancestor. That would mean, would it not, that the twelve traits jumped aboard all at once in a single speciation event? This does not accord with the gradual nature of evolution that I thought was the dominant view. The synapomorphies can be grouped, somewhat, cutting down on the total number; the two listed items relating to the fourth trochanter of the femur can surely be combined into one. We are left, however with changes to the skull roof, the cervical vertebrae, the limb bones, and the pelvis, all of which happened at once according to Nesbitt. Can a case can be made out that these are interdependent; that no one change could have occurred without all the others if the animal was to remain functional? If not, the proposition that all twelve traits are synapomorphies of the dinosaurs is difficult to accept. Peter Brown (talk) 23:19, 2 September 2013 (UTC)
If any group has a large number of synapomorphies, doesn't that just mean there's a relatively large gap between it and more basal groups? That is, we would expect the number of synapomorphies to drop steadily as we find more near-dinosaurs. MMartyniuk (talk) 21:15, 3 September 2013 (UTC)
Exactly. However, this also means that those near-dinosaurs were the first species showing the apomorphies and thus are implicitly referred to by the original larger list of synapomorphies. Also, those apomorphies might first have been acquired by very basal dinosaurs, although this requires a degree of parallel evolution. The synapomorphies were in such cases not changes in the real last common ancestor but in a range of species. It is this range that is represented by the larger list.--MWAK (talk) 09:09, 4 September 2013 (UTC)
Well, these traits would not have to be acquired all at once. Indeed, at the moment of speciation, e.g. by allopatry, the last common ancestor of dinosaurs might well have been morphologically indistinguishable from its ancestor. During the, perhaps many, million years of its subsequent existence — of course the "ancestor" is now seen as an ancestral species, not a single individual — new traits could gradually have evolved. However, it is indeed quite implausible (though not impossible) that the actual last common ancestor of the Dinosauria really was the species showing for the first time these twelve innovations. The high number in all probability indicates a serious gap in the fossil record. You see, in cladistics, the "last common ancestor", when related to a set of synapomorphies is always a methodological fiction. It might truly have been a single species but more often will have been a group. The data — the actually discovered extinct and extant species — do not allow us to resolve this group and therefore we treat it as if it were one species. One has to keep this in mind :o).
By the way, in general traits should only be combined if there is a material implication.--MWAK (talk) 06:50, 3 September 2013 (UTC)
So a last common ancestor is usually not a species but a species group? And what species are in the group depends on what, in our present state of knowledge, we are able to resolve? "Synapomorphy" is defined in terms of LCA, so this would mean that what traits are synapomorphies is also relative to our state of knowledge. If we called something a synapomorphy last year but refuse to call it one this year, apparently we need not have changed our minds; due to new discoveries and enhanced technology, the scope of the term can change from year to year so that a 2012 synapomorphy need not be a 2013 one. Is this made clear anywhere in Wikipedia? For starters, Last common ancestor#MRCA of different species and Synapomorphy are seriously in need of updating.
In the Erythrosuchus article, it is stated,
The hypothetical last common ancestor of archosaurs is thought to have shared many features with Erythrosuchus, many of which are found in the braincase.
Is the "last common ancestor" in this context a species group? Does calling it "hypothetical" mean that no fossil in any of the group members has been found? Or is it a particular species, and the implication of "hypothetical" is that we have no fossils in that species?
Similar questions arise for a huge number of articles. Peter Brown (talk) 15:59, 3 September 2013 (UTC)
"So a last common ancestor is usually not a species but a species group? " I guess that depends on how you define "species", but I think it would be better to think of the LCA as a population. When two populations within a species become isolates, they remain the same species for quite a while under most species concepts before speciation occurs. MMartyniuk (talk) 21:17, 3 September 2013 (UTC)
The term "group" isn't mine; I'm trying to understand MWAK's statement
You see, in cladistics, the "last common ancestor", when related to a set of synapomorphies is always a methodological fiction. It might truly have been a single species but more often will have been a group. The data — the actually discovered extinct and extant species — do not allow us to resolve this group and therefore we treat it as if it were one species.
You prefer populations as ancestors, which is in better accord with the Phylocode than MWAK's groups. Do you agree with MWAK that LCA is "a methodological fiction"? Peter Brown (talk) 21:40, 3 September 2013 (UTC)
"Do you agree with MWAK that LCA is "a methodological fiction"" It depends on the context. Certainly, any two given eukayotic organisms had a singe LCA that was a real genetic population of organisms. My understanding, which could be wrong, is that not only is the actual LCA incredibly unlikely to be preserved in the fossil record due to its incompleteness, but that even if this ancestor does indeed exist in a form that can be coded, cladistic methodology will recover it as a basal sister group rather than as an ancestral node. LCAs exist, but cladistic methodology alone cannot tell us what they are without extra interpretation of the data. For example, it is possible that the population of ceratopsids that contains the type specimen of Rubeosaurus is directly ancestral of the population that contains the type specimen of Einiosaurus, which in turn may be ancestral to the clade Pachyrostra in an anagenic lineage. Nevertheless, cladistic analyses usually recover the former two specimens as successive outgroups to pachyrhinosaurs, which is not inconsistent with the hypothesis that this is a single lineage--it's just an artifact of how cladistic analyses work. In the above example, the last common ancestor of Rubeosaurus ovatus + Pachyrhinosaurus canadensis (=clade Pachyrhinosaurini) would be Rubeosaurus ovatus itself. But because phylogenetics does not allow for paraphyletic taxa, this can't be expressed directly, though we must realistically acknowledge that all species evolved from some other species, and thus most species are paraphyletic in one way or another. MMartyniuk (talk) 10:58, 5 September 2013 (UTC)
MWAK carefully distinguishes the "actual last common ancestor", a real population or whatever, from "the last common ancestor when related to a set of synapomorphies" which is always a methodological fiction. Do you agree that there is an important distinction here? I don't think that coding an ancestral group as a basal sister is really "fictional", since it represents a hypothesis that is correct for all we know. Peter Brown (talk) 17:13, 5 September 2013 (UTC)
Well, a "last common ancestor" to which synapomorphies are attributed in a cladistic analysis will usually be a species group. The actual last common ancestor is by definition a species or a certain set of individuals (depending on the definition).
Indeed, what we know to have been the synapomorphies, is dependent on our present state of knowledge. As our knowledge increases, the number of synapomorphies will eventually decrease and the number of species factually included in the species group will decline, approaching the one species that is the actual last common ancestor. That actual last common ancestor is referred to in a clade definition; such a definition does not indicate a species group.
The sentence "The hypothetical last common ancestor of archosaurs is thought to have shared many features with Erythrosuchus..." confuses the actual last common ancestor ("the hypothetical last common ancestor of archosaurs" — it is both actual and hypothetical, i.e. not known to have been found yet) with the fictional last common ancestor (the species group sharing those synapomorphies with Erythrosuchus). The fact that we are unable to resolve a group does not necessarily mean we haven't found any fossils of these species, just that we as yet don't know this.--MWAK (talk) 09:09, 4 September 2013 (UTC)
You write of "what we know to have been the synapomorphies". Based on the following sentence, I think you mean "what are the synapomorphies." The phrase "have been" refers to an indefinite time in the past and, as you say, the set of synapomorphies varies with the state of knowledge. Prior to 1842, there were no dinosaur synapomorphies because the dinosaur-concept hadn't even been formulated.
Such details aside, I find your POV quite convincing. Is it OR or can you provide sources so that these ideas can be incorporated in Wikipedia articles?
Peter Brown (talk) 16:52, 4 September 2013 (UTC)
Ah, I fear in many matters I'm rather a Realist :o). Certainly I do not see the synapomorphies as merely (I would say, being a Realist) a social construct.
"Hidden species" are a well-known problem in the phylogenetic species concept. Our discussion is perhaps simply about the relation between the phylogenetic species concept and the biological species concept. An elegant solution was offered by this article: Pleijel F. and Rouse G.W., 2000, "Least-inclusive Taxonomic Unit: A New Taxonomic Concept for Biology", Proceedings of the Royal Society of London – Series B: Biological Sciences 267: 627–630. The LCA is then in cladistic analyses a LITU, without any claims about it being a species. In most Wikipedia articles it is unnecessary to reveal such implicit problems.--MWAK (talk) 07:01, 5 September 2013 (UTC)
I'll take a look at the paper. You have written:
"in cladistics, the 'last common ancestor', when related to a set of synapomorphies is always a methodological fiction."
Are the synapomorphies themselves methodological fictions even though they're not social constructs? Since synapomorphies are generally defined in terms of LCAs, I would expect them to be no less fictional. Peter Brown (talk) 17:38, 5 September 2013 (UTC)
The traits as such are to be considered real; their combination in a set of synapomorphies is in cladistics a methodological fiction: you pretend that there is a single species for the first time showing certain modifications, while it is likely these modifications were acquired by a range of species. However, a degree of fictionality has always been overt, as such a set clearly functions as an hypothesis.--MWAK (talk) 08:22, 6 September 2013 (UTC)

Missing citations

This article is lacking citations for many sentences and even paragraphs. Might threaten its status as FA. FunkMonk (talk) 11:18, 5 October 2013 (UTC)

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