Talk:Dinosaur/Archive 8

Page contents not supported in other languages.
From Wikipedia, the free encyclopedia
Archive 5 Archive 6 Archive 7 Archive 8 Archive 9 Archive 10 → Archive 15

Untitled

Folks - Please sign your messages with ~~~~. Please also try to add appropriate section headings if you are beginning a new topic of discussion. Please add new discussion to the bottom of the page. - UtherSRG 12:19, 3 Jun 2004 (UTC)

Overhaul

Well, with material archived, I suppose it's not a bad idea to do this as a clean slate. From what I can tell, here are the suggestions that have been brought up but not yet addressed or acted on:

Structure:

  • Moving Paleobiogeography to follow Origins;
  • Moving Classification after Extinction;
  • Shuffling individual topics in "Feathers and the origin of birds" and/or reworking redundancies with Physiology (Lungs, Heart, and Gizzard);
  • Moving some of the material from the lead of Paleobiology to Dinosaur Renaissance;

Individual topics:

  • Various studies in Behavior are brought up, but their results are not given;
  • Limitations of the dinosaurian body plan;
  • The discussion of dino metabolism omits growth rates and erect limbs;
  • The feather section should say that feathers are only known in coelurosaurs;
  • The section on lungs is missing Ruben's views;
  • An elementary error concerning distinctive features of dinos (maybe resolved?);
  • Diagram of "normal erect" and "pillar erect" hip joints would be helpful;
  • References for several topi cs;
  • Reference formatting;
  • Wikilink locations, and adding relevant wikilinks;
  • The following discussion on the extinction section, which I decided I couldn't summarize.

Feel free to add anything from November/December that was brought up and not yet addressed, but I forgot to add. J. Spencer (talk) 03:58, 2 January 2008 (UTC)

J. Spencer, you really are incredibly honest!
Looking at the results of your work, I think we should consider grouping "Origins and early evolution", most of "Evolution and paleobiogeography" and "Extinction" as a sequence which gives a summary of dino history, before going on to more specific topics. If the "history of dinos" material contained a few approx dates, that would also help to dispel misconceptions that all sorts of dinos were contemporaries and / or lived in the same places (as shown in the Jurassic Park movies; OK, in the story they were resurrected and genetically engineered, but many people may have missed the implications of that). In particular I think the article should point out that the tyrannosaur-ceratopsian-hardosaur fauna often used to represent the Cretaceous is localised to N America and E Asia (with a few specimens in W Europe) and that scaled-up versions of the "typically Jurassic" allosaur-brontosaur fauna appeared to dominate many other areas throughout the Cretaceous. Sorry for not suggesting this before you started work, as I know it will mean combing through "Evolution and paleobiogeography" and finding new locations for any points that don't fit into a historical narrative.
Re "Behavior", the article admits it's rather speculative, so the lack of firm conclusions is not a problem. But I can see where one small correction is needed: "(pack hunting) is not found among the modern relatives of dinosaurs (crocodiles and other reptiles, and birds)" is questionable because I've seen a BBC documentary in which one species of hawk hunted in packs of about 5, in the wild and without being trained (can't remember the birds' name, dammit; i think it was in Africa).
In "Physiology", "However, so far this theory fails to account for the vast number of dog- and goat-sized dinosaur species which made up the bulk of the ecosystem during the Mesozoic Era" (last sentence) has 2 problems: it's inconsistent with "average dinosaur weight is about 100 kilograms (200 lb)" in "Size of dinosaurs"; and I expect that the "bulk of the ecosystem" was bacteria and invertebrates, as is generally agreed for the modern world (by total weight as well as ecological importance).
Re "Distinguishing features", I'd prefer "Such common features across a taxonomic group ..." as they are sometimes subtle than "strutures" would suggest. The error that I spotted a while ago appears to have gone, at least nothing shouted at me. It would still be nice to have a simple pic to illustrate hindlimb posture and hip joints (sprawling, "dino-mammal erect" and "pillar-erect") - stick figures will do, and could be quite small.
Re "extinction", I agree with your "following discussion on the extinction section, which I decided I couldn't summarize" - I think we need to sort out what goes in which article before we can finalise Dinosaur.
I've been think about the "Classification" section. I still think the full classification should be fairly late, because it won't be of immediate interest to the general reader; but I see you point about "establshing the cast list", especially as a preparatory step for "Paleobiogeography". Perhaps it would be a good idea to: move the full "Classification" to a later position; in its place add a simple "Classification overview" and very simplified cladogram, like the first one in "Evolution of mammals" (section "The ancestry of mammals"), and explain that the terms introduced there are used in most of the article; make the terms used in in most of the article consistent with those in "Classification overview" or add short local explanations, e.g. "tyrannosaurids are the tyrannosauroids which are most closesly reated to T rex"; avoid any mention of -inae and -ini, which are in any case the most volatile (e.g. how close were Daspletosaurus and Tarbosaurus to T rex?).
I think the other outstanding items you mentioned can be added fairly easily, with low risk of troublesome side-effects (isn't that a relief!). Philcha (talk) 12:03, 4 January 2008 (UTC)

Here's a sketch of a reduced classification. I think the sauropodomorphs and ornithischians are all right, but the theropods still sprawl.

In order of appearance, herrerasaurs, coelophysoids, spinosauroids, brachiosaurids, and heterodontosaurids may be most expendable.

J. Spencer (talk) 16:39, 4 January 2008 (UTC)

Great, that has exactly the level of detail I was thinking of! And I like your short descriptions. Re "expendables", I suggest it's best to review them when most other edits are done; the short classification is only to help readers with clades named in the article.
As far as the presentation goes, I'd prefer "ACSII" art rather than the "clades" template, for the reasons I mentioned in our disussion at Talk:Evolution of mammals, especially that in the template root and stem clades appear half-way down. If you'd be happy with that, I'd be prepared to do the grunt work.
PS: There's been no movement yet on my proposal to use suitably CSS-styled nested lists with or without dynamically expanding / collapsing sub-trees. Would you be happy with a nested bullet list so that we could just retrofit the CSS etc. if my proposal gets implemented some day?
PPS Harris' Hawk is the pack hunter I saw on TV, but this NY Times article lists other birds that hunt in packs - a lot more than I realised. I think we need to think very carefully about how to phrase the bit in Dinosaur about pack hunting, and probably hunt for good citations first.Philcha (talk) 17:25, 4 January 2008 (UTC)
Is a nested bullet list different from the classification format that's already in the article? For a sketch, I was thinking of using a format similar to what I made above, as it's not an actual classification so much as a highlight reel. I'd rather not use an ASCIIgram, if we don't need to.
If you're interested, send me an email and I'll send you a pdf of the 2007 article on theropod pack hunting or the lack thereof. Whether you buy the interpretation or not, it's an interesting read. J. Spencer (talk) 20:11, 4 January 2008 (UTC)
Nested bullet list is what you used in the article and the "short" version above - I'm happy with that.
Yes, please email me the article on theropod (not) pack hunting!.
But we still need to correct the article's current statement that birds don't pack-hunt. Philcha (talk) 23:27, 4 January 2008 (UTC)
I must have been working too fast when I wrote it; I hadn't realized I'd said "none" pack-hunt. The article itself mentions exceptions such as Harris's Hawks. It's just uncommon among diapsids. J. Spencer (talk) 00:38, 5 January 2008 (UTC)

Here's kind of a radical idea: does this article need the full classification it presently has, or could it get by with a simplified overview like above and a link to the detailed page? J. Spencer (talk) 17:39, 5 January 2008 (UTC)

I'd be happy with that. As a "root" article Dinosaur has to act a portal to other articles on dozens of aspects of the subject, so there are a lot of topics it can't cover in great detail. It might be a good idea to check though the text in the longer "Classification" section and see what needs to be transferred to the shorter one in Dinosaur and / or to [[Dinosaur classification]. Philcha (talk) 18:02, 5 January 2008 (UTC)

Extinction of the dinos

01:09, 13 March 2008 (UTC)01:09, 13 March 2008 (UTC)~ I think that there should be a mention that the meteor impact in the Yucatan probably caused the volcanic eruptions in India. My article http://charles_w.tripod.com/decca_traps.pdf indicates the high probability that India (which 65 mya was at the antipod of the Yucatan) had the crust disrupted by the seismic waves generated by the meteor impact. D c weber (talk) 01:09, 13 March 2008 (UTC)d_c_weber 20080312

Interesting, but a little suspicious becuase it seems to cite primarily online sources, and doesn't have any actual publication info. Where was this published? Dinoguy2 (talk) 02:59, 13 March 2008 (UTC)

I think some of the content in "Extinction" and Cretaceous–Tertiary extinction event should be shuffled between the 2 articles:

  • "Extinction" should cover the debate about how fast dinos became extinct (several analyses of Hell Creek by Fastovsky and co. argue it was abrupt; I don't know the latest consensus).
  • "Extinction" should keep "Paleocene dinosaurs?".
  • A lot of the material about patterns of extinction and causes should be moved to Cretaceous–Tertiary extinction event, with brief notes and a cross-link rermaining in Dinosaur. In particular "Extinction" in Dinosaur should avoid the impression of being committed to one theory (impact) and should briefly mention the other leading contender, Deccan Traps eruptions. Philcha (talk) 11:54, 23 December 2007 (UTC)
Dinosaur already has a section on both the impact extinction theory and the deccan trap extinction theory. What it is really missing is the 'they were already on their way out' theory, which is Dodson's and some other folk's view, and one of the leading contenders on dinosaur extinction theories. Firsfron of Ronchester 12:01, 23 December 2007 (UTC)
Going through "Extinction" (Dinosaur) in detail: the 1st para is good but should mention vegetation, while the rest of the intro mentions factors which are not discussed in Cretaceous–Tertiary extinction event (ice caps, temperature, oxygen level) and whose relevance is not made as clear as it should be in "Extinction" (moving "Some scientists hypothesize that climate change, combined with lower oxygen levels, might have led directly to the demise of many species" before the material about climate would help); too much about the details of variations on the impact theory and not enough about how an impact might have caused a mass extinction ("nuclear winter", rain of red-hot debris, acid rain, longer-term greenhouse effect); Deccan trap content OK but could be shorter, and I think the stuff about Alvarez' view of the Deccan Traps should move to Cretaceous–Tertiary extinction event.
To get the 2 articles to support each other with minimal duplication I suggest: incorporate content into Cretaceous–Tertiary extinction event as suggested above, so that Cretaceous–Tertiary extinction event becomes the main source amnd "Extinction" only summarises selected items from it (probably not a quick job, as Cretaceous–Tertiary extinction event is an intrinsically complex subject); start "Extinction" with review of extinction patterns (extinction of dinos fast or slow, Fastovsky vs Dodson; Paleocene dinos; Hell Creek {AFAIK} the only boundary-spanning terrestrial fossil bed, may not be globally representative, but if others have been discovered recently we need to have a good look at the refs before editing anything; brief list of other casualties); brief review of major explanatory hypotheses and killing mechanisms, with strong recommendation to read Cretaceous–Tertiary extinction event for fuller description and explanation. Philcha (talk) 12:47, 23 December 2007 (UTC)
Extinction of the dinos - could flowers have killed them?

I was just watching a show about the first flowering plants ... they appeared at about the time the dinosaurs died ... could this be related? Flowers are only small but there would be several major changes: populating the planet with a new species of plants must have a huge effect. Also the pollen released causes all sorts of allergies to peope today ... and we have millions of years of evolution to deal with these small particles that get right into our lungs. Just a silly thought - would love some feedback from someone who knows about the likely effects. —Preceding unsigned comment added by 210.84.37.16 (talk) 10:41, 17 February 2008 (UTC)

Actually, flowers appeared about halfway through the Cretaceous, so dinosaurs had 40 or 50 million years of living alongside them and eating them. J. Spencer (talk) 16:10, 17 February 2008 (UTC)
Flower power! I love it! Perhaps it took a while to grow allergic? This is great as an alternative theory to meteor impact. We used to laugh when seeing geologists drawing causal relationships from even very strong statistical correlations alone, without evidence of any real causal mechanism. This is a great contribution to the classroom. Geologist (talk) 00:45, 20 March 2008 (UTC)

Article needed on dino paleobiogeography?

While reviewing J. Spencer's recent edits (see thread "Overhaul" above), I realised that the distribution of dinos across geography and time is potentially a very large topic and also probably quite volatile, considering the rate at which discoveries are pouring out of China and also Africa & S America. I think we should consider creating an article "Dinosaur paleobiography: distribution of dinos across geography and time" to cover it. I know the title I've suggested is rather long, but "paleobiogeography" is not a term that general readers will search for. I suggest such an article should be arranged chronologically, and by continent or region within time period. Or it could have 2 major sections, one chronological and the other summarising where and when various types of dinos lived. PS: I've searched Wikipedia for "dinosaur paleobiography time period" and "dinosaur paleobiography " and go no hits at all. Philcha (talk) 12:18, 4 January 2008 (UTC)

We could simplify it further, and call it "Dinosaur distribution"/"Distribution of dinosaurs". J. Spencer (talk) 20:21, 4 January 2008 (UTC)
I'd be happy with budding the section off into its own article at some point; my one concern is that it might be seen as "dinocruft". J. Spencer (talk) 20:17, 4 January 2008 (UTC)
What kind of taxon is dinocruft? Philcha (talk) 20:39, 4 January 2008 (UTC)
Something of interest only to a very narrow audience, and thus liable to be deleted. Someone who's active at Articles for Deletion would be able to explain the concept better. J. Spencer (talk) 22:49, 4 January 2008 (UTC)
A sort of nomen dubium :-)
But seriously, a paleobiogeography article would make the points I mentioned above (different combinations of genera at different times and places). How many people it appeals to depends on how we present it in the linking page(s). Your comment does imply that the idea needs further discussion. Come on people, let's have some thoughts!
PS: It would not actually have helped if I'd spelt "paleobiogeography" correctly - searching Wikipedia gave me nothing much for "dinosaur paleobiogeography" Philcha (talk) 23:21, 4 January 2008 (UTC)
I can't imagine a well written and well sourced article on dinosaur distribution being deleted as "cruft". That may apply to pop culture topics, but I don't think it concerns scientific articles. Mgiganteus1 (talk) 23:46, 4 January 2008 (UTC)

Cutting down the bird section

I hadn't really realized it before, but Origin of birds contains essentially a copy of the bird section of this article. In my view, since this is the case, there is no need for this article to literally duplicate what is legitimately the territory of Origin of Birds. I'd suggest an historical overview (Huxley, Heilmann, Ostrom, and the modern finds) with a recognition of the criticism, and a discussion of feathers and some other anatomical material, but much more concise. Also, any of the subsections that is more detailed or up-to-date here should be copied to Origin of Birds to improve that article. J. Spencer (talk) 04:08, 6 January 2008 (UTC)

My first reaction was "Good, as per WP:Summary style." But then I looked at Dinosaur and concluded you were talking about section "Feathers and the origin of birds". That section contains a lot of material that would be important for dinos even if birds had never evolved. In particular it presents fossil evidence that's relevant to the debate about "Physiology".
So I'd be inclined to move "Feathers and the origin of birds" before "Physiology", in order to present evidence before analysis. I'm not sure that "Feathers and the origin of birds" is a good title for the section, and would suggest "Bird-like features of dinosaurs" - that would enable readers to understand why even a lot of 19th century scientists thought of dinos as very active animals (I don't know whether any stated opinions on thermoregulation), and would also alert them to the coming link to Origin of birds.
If Dinosaur is structured as I've just suggested, I think the history of the dino-bird link (Huxley, Heilmann, Ostrom, etc.) should been in Origin of birds, with just a note in Dinosaur that the topic has been raised several times (names and dates) before it became the consensus that birds evolved from small theropods.
Then move to Origin of birds any content that seems too specific / detailed for Dinosaur.
How does that sound? Philcha (talk) 09:23, 6 January 2008 (UTC)
I might have to mock up an example of what I'm thinking of. Perhaps:
"The possibility that dinosaurs were the ancestors of birds was first suggested in the 1860s by Thomas Huxley.(ref) After the work of Gerhard Heilmann in the 1920s, the theory of birds as dinosaurs was abandoned in favor of generalaized thecodont ancestors, with the key piece of evidence being the supposed lack of clavicles in dinosaurs;(ref) as later discoveries showed, clavicles were not actually absent.(ref) In the 1970s, John Ostrom revived the dinosaur-bird theory,(ref) which gained momentum in the coming decades with the advent of cladistic analysis,(ref) and a great increase in the discovery of small theropods and early birds.(ref) Of particular note has been the fossils of the Yixian Formation, where a variety of theropods and early birds have been found, often with feathers of some type.(ref) Birds share over a hundred distinct anatomical features with theropod dinosaurs,(ref) which are now generally accepted to have been their closest ancient relatives.(ref) They are most closely allied with maniraptoran coelurosaurs.(ref) [a sentence follows about the opposition; the following is true but uncharitable: A few holdouts persist, most vocally ornithologists Alan Feduccia and Larry Martin, who seem to be opposed to linking the concept "dinosaur" with "bird", as they have proposed that maniraptoran theropods are the ancestors of birds but themselves are not dinosaurs, only convergent with dinosaurs.(ref)]
Next: subsection on anatomical links, including feathers, skeleton, lungs, and reproduction. The heart should be with physiology, and I personally am very uncomfortable with the utility of the gizzard when so much better evidence is present.
Some of the present material is useful for physiology, but Origin of birds#Features linking birds and dinosaurs and Dinosaur#Feathers and the origin of birds shouldn't be nearly exact copies. The detail should be in Origin of Birds, and the general overview should be here. J. Spencer (talk) 16:07, 6 January 2008 (UTC)
Maybe my last post was so verbose it obscured what I intended. What I thought was:
  • The history and controversy relating to dinos as ancestors of birds should be covered in detail in Origin of birds.
  • The structure / order in Dinosaur should be:
    • "Bird-like features of dinosaurs" - saying: the resemblance was noted in the 19th century (names and dates), the modern consensus is birds arose from small coelurosaurs, but there are a few hold-outs - see also Origin of birds.
      • Feathers
      • Skeleton
      • Reproductive biology
      • Lungs (or "Respiration")
      • Heart and sleeping posture
      • Gizzard
    • Physiology
I think that flows better because: it presents (alleged) evidence relevant to Physiology (especially thermoregulation) before getting into the analysis / debate about thermoregulation; it prepares the reader for the link to Origin of birds.
It's difficult to avoid some duplication of the bird-like features because they're relevant to both Origin of birds and Physiology (on which there is also a separate article and a related controversy). Philcha (talk) 16:45, 6 January 2008 (UTC)
Your structure for the section is close to what I was thinking, but I'd like Heart to move to Physiology, since it's not specifically about birds, and to remove Gizzard altogether, since gastroliths in general are found in a lot of different things, have a very patchy purported distribution in dinosaurs (Psittacosaurus, Lourinhanosaurus, Massospondylus, Sinornithomimus), and may not actually be gastroliths in most dinosaurian cases, per Oliver Wings' recent work (can be found here). J. Spencer (talk) 18:03, 6 January 2008 (UTC)
I agree about Heart. I understand your reservations about Gizzard stones, but it's my impression (possibly wrong), that this is still a common idea in pop science, and I think it's part of our job to deal with misconceptions / obsolete ideas. Why not just say "it used to be thought that ... but ..."? Philcha (talk) 21:27, 6 January 2008 (UTC)
In that case, would it be better off in Origin of Birds? I'm gauging the appropriate level of detail for dinosaur subtopics. J. Spencer (talk) 00:06, 7 January 2008 (UTC)
The way I was seeing it, it's more relevant to Dinosaur, because in order to support a high metabolic rate dinos would have needed to digest food fast, therefore needed something to grind their food. Hardosaurs and ceratopsians had massive dental batteries, but they were only 2 rather late lineages; sauropods and theropods would have needed something else, and apparent finds of gizzard stones appeared to fit the bill. Of course that could also be treated as a case for putting gizzard stones in the article dealing with dino metabolism. But Dinosaur gives a summary of the dino metabolism debate, so a summary of gizzard stones seems necessary in Dinosaur. Philcha (talk) 00:57, 7 January 2008 (UTC)

I've added an overview and begun trimming. As usual, changes are completely negotiable. I pulled out a few chunks wholesale:

"Feathered dinosaurs discovered so far include Beipiaosaurus, Caudipteryx, Dilong, Microraptor, Protarchaeopteryx, Shuvuuia, Sinornithosaurus, Sinosauropteryx, and Jinfengopteryx. Dinosaur-like birds like Confuciusornis, which are anatomically closer to modern avians, have also been discovered. All of these specimens come from the same formation in northern China. The dromaeosauridae family in particular seems to have been heavily feathered, and at least one dromaeosaurid, Cryptovolans, may have been capable of flight."

(We've got Feathered dinosaurs for lengthy lists; Shuvuuia is not from the Yixian, and "heavily feathered" is kind of an odd description that goes nowhere)

"Furthermore, it is increasingly clear that the relationship between birds and dinosaurs, and the evolution of flight, are more complex topics than previously realized. For example, while it was once believed that birds evolved from dinosaurs in one linear progression, some scientists, most notably Gregory S. Paul, conclude that dinosaurs such as the dromaeosaurs may have evolved from birds, losing the power of flight while keeping their feathers in a manner similar to the modern ostrich and other ratites."

(good point, but completely out of place in skeletal anatomy and had no comparable section elsewhere for the discussion, and would benefit from biplane microraptorans as an example of odd offshoots)

The Massospondylus embryo was moved to Behavior in Paleobiology because the bird connection was not expressed, and I removed the line about regurgitation as speculation. J. Spencer (talk) 03:48, 1 February 2008 (UTC)

Common names

Why no one give dinosaurs any common names? How come we don't give them common names and be the first to do that? Here is a list of some of the dinos that have common names:

  • Ajax’s apatosaur (Apatosaurus ajax)
  • Marsh’s apatosaur (Apatosaurus excelsus)
  • Louise’s apatosaur (Apatosarus louisae)
  • Parvus apatosaur (Apatosaurus parvus)
  • Eobrontosaur (Eobrontosaurus yahnahpin)
  • Colorado giant (Supersaurus vivianae)
  • Cope’s giant (Amphicoelias fragillimus)
  • Southern giant (Australodocus bohetii)

--4444hhhh (talk) 18:40, 12 January 2008 (UTC)

Wikipedia is not the place to discuss giving dinosaurs common names. Wikipedia forbids original research: "Wikipedia does not publish original thought—all material in Wikipedia must be attributable to a reliable, published source." Being the first to publish something is original research. Wikipedia is just an encyclopedia; you would not see the editors of The World Book Encyclopedia proposing to invent their own names for dinosaurs and stick them in their encyclopedia, would you? Finally, names like "Colorado giant" are bound to be confusing, as 'giant' can often refer to excessively large human beings. Firsfron of Ronchester 20:23, 12 January 2008 (UTC)
Yeah, but then why dinosaurs don't have common names then?--4444hhhh (talk) 20:33, 12 January 2008 (UTC)
Most fossilized animals and plants don't have common names. Firsfron of Ronchester 20:40, 12 January 2008 (UTC)
Why? Is it because they're two many of them? But then Carl Linnaeus gave all the living (and maybe extinct) binomial nomenclature to all of them and there were encyclopedia way before binomial nomenclature. And to me Wikipedia isn't really encyclopedia because it has movies and shows which no encyclopedia, that I know of, has.--4444hhhh (talk) 20:58, 12 January 2008 (UTC)
Ahem. :) Sheep81 (talk) 21:15, 12 January 2008 (UTC)
No I'm meant that the editors of The World Book Encyclopedia don't include films and shows.--4444hhhh (talk) 21:27, 12 January 2008 (UTC)
Well, you said "Wikipedia isn't really encyclopedia because it has movies and shows which no encyclopedia, that I know of, has." World Book Encyclopedia has a number of articles on TV programs and films, and there are a number of encyclopedias, such as (Sheep's example, above) The Film Encyclopedia, which list thousands of them. Wikipedia is both a general encyclopedia and a specialized encyclopedia. It can incorporate elements from both The World Book and The Film Encyclopedia, and still be a "real" encyclopedia. What it can't do is be a publisher of original research, such as names that its own editors coin for things: "real" encyclopedias don't do that. Firsfron of Ronchester 21:42, 12 January 2008 (UTC)
Okay, fine, then but really why do a lot of people don't give common names to extinct animals (like Carl Linnaeus gave all the living a binomial nomenclature)?--4444hhhh (talk) 21:47, 12 January 2008 (UTC)
I suppose because nobody every really thought it was that important. Maybe you can start your own website where you give common names to dinosaurs? Sheep81 (talk) 22:58, 12 January 2008 (UTC)
Common names for living species were around before any scientific classification such as Carl Linnaeus' (in fact his genus names were mostly just the common names in the Latin language). There are no common names for dinos because there was no-one around to give them common names (not even Raquel Welch or Victor Mature). Philcha (talk) 23:36, 12 January 2008 (UTC)
Also remember that even many living animals don't even have official common names. I think birds and fish, for example, have their own system of naming almost similar to the ICZN. But many other kinds of animals common names just depends on the region you live in. Dinoguy2 (talk) 01:33, 14 January 2008 (UTC)

Misplaced sentence in "Origins and early evolution"?

"Origins and early evolution" has the sentence "Early considerations of dinosaur evolution had dinosaurs as polyphyletic, with multiple groups of unrelated "dinosaurs" evolving due to similar pressures, but dinosaurs are now known to have formed a single group" in the middle of what appears to be a discussion of how fast dinos diversified and became the dominant terrestrial vertebrates. I think it would read better as the first sentence of that para. Philcha (talk) 15:38, 17 January 2008 (UTC)

Done. Philcha (talk) 14:44, 21 February 2008 (UTC)

Shorter classification

I've inserted the shorter classification discussed above (including brief descriptions), and commented out the long version. Philcha (talk) 16:30, 17 January 2008 (UTC)

Looks ok to me, but given the widely disparate definitions for "bird", maybe this should be 'Avians (modern birds and extinct relatives)' or something? Dinoguy2 (talk) 17:40, 17 January 2008 (UTC)
By "widely disparate definitions for 'bird'", are you referring to ideas like Avialiae" and the secondary flightlessness of 'raptors? At first site I liked your suggestion of "Avians (modern birds and extinct relatives)" but then the phrase "extinct relatives" started nagging at me - it could mean the dodo, or (for Greg Paul) some dromaeosaurs, tho' I suspect you meant enantiornithines and hesperornithnes. How about "birds (including some groups that became extinct about the same time as non-avian dinosaurs)"? Philcha (talk) 10:03, 18 January 2008 (UTC)
That doesn't really get around the problem though--In Aves sensu Gauthier, enantiornithes for example would not be "birds" if you equate "bird" with Aves. The original definition of Aves was apomorphy-based on feathers. I personally think it's a mistake to automatically equate "bird" with Aves... Actually my original suggestion doesn't get around this problem either, come to think of it. Something like 'Avialans (flying feathered dinosaurs)' would cover all the bases. Or we could leave it as is, but I'd still prefer 'Aves (birds)' to using Bird as the main linked label. It sticks out as an undefined vernacular name among a list of taxa. Dinoguy2 (talk) 16:32, 18 January 2008 (UTC)
Thanks for suggesting "Aves (birds)", I'll go with that for now. but you're right, it should be possible to work out a phrase that's accessible but more precise, without committing to an specific taxonomy such as Gauthier's. Any way this is only the "short" classification. Philcha (talk) 10:03, 20 January 2008 (UTC)

Medullary bone

The mention of medullary bone links to marrow, which suggests that medullary bone = marrow. This is not true, see for example Cortical/medullary bone; mineral storage or Medullary bone of piglets - the latter ref makes it clear that medullary bone is different from (and crowds out) the stuff that makes blood cells. I've reworded the relevant part of "Reproductive biology". Philcha (talk) 17:30, 17 January 2008 (UTC)

The Term "Prehistoric"

In several of our articles we use the term "prehistoric birds" to describe Mesozoic species. I fear that this may be an imprecise term. Since, to my knowledge, history originates with writing about 9,000 years ago, the "historic" part is a tiny fraction of even the human past. All extant bird species originated before the beginning of written history, meaning that all birds ever known are prehistoric, meaning that the term "prehistoric bird" carries no distinction in meaning from just "bird". Dinoguy2 (talk)(UTC) and I considered "fossil birds", and "extinct birds", but those are also a bit imprecise. There are fossils of extant species, and many birds became extinct after they were experienced directly by our civilization and collected and studied by modern science. We would like to recommend "Mesozoic birds" as a substitute.Jbrougham (talk) 18:01, 19 January 2008 (UTC)

This Article

The study of dinosaurs today is controversial. There aren't many jobs in the field, the work is hard, the pay is meager, and careers are built on unprovable theories. Thus, many aspects of dinosaur studies are influenced by personality. On the other hand, the rewards of a career in dinosaur palaeontology are incomparable. In skimming this article for the first time, two things jumped out at me:

(1) There is an awful lot about birds at the forefront of the article, a clear effort to promote the idea that birds are descended from dinosaurs. This idea is based on cladistic analyses which indicate that birds are descended from early avian dinosaurs. That word avian has even crept into dinosaur systematics in recent years. Perhaps there is discussion of the alternative viewpoint (that the ancestry of birds predates dinosaurs) but I didn't see it.

It is important to keep in mind that cladistics is a tool, like a wrench or a pregnancy test. If used improperly, it can give bad results. Much of what we know about dinosaurs is still just theory. Having said that, the evidence does support the theory that birds are descended from early dinosaurs. A brief discussion of homoplasy (convergent evolution) somewhere in the article might be appropriate.

(2) In the first section of the article (near the Stegosaurus photo), there is the following sentence:

Paleontologists mostly use cladistics, which classifies birds as dinosaurs, but some biologists of the older generation do not.

Ignoring the grammatical shortcomings of that sentence, what is meant by "the older generation"? Is that anyone over 40, or does the writer mean folks like Cope, Marsh, and Lull..? This is the sort of partial language that rubs people the wrong way and causes them to take sides based on something other than the evidence. Having said that, let me add that I am a confirmed (if reluctant) cladist. NOTE: if this section isn't in the right place, please move it but do not simply delete it. (Tortugadillo (talk) 07:45, 31 January 2008 (UTC))

Well, it's not just cladistics that pair birds and maniraptorans, but I agree that there is too much detailed bird-dinosaur link material in this article that is supposed to be about dinosaurs in general, and is especially redundant when we have Origin of birds that includes a near-exact copy of the same information. J. Spencer (talk) 14:15, 31 January 2008 (UTC)
I cut the "which classifies" clause from that sentence as a preliminary fix. J. Spencer (talk) 03:50, 1 February 2008 (UTC)

Ostrom found that birds were dinosaurs and he was not a cladist. So did Huxley, I guess, and he also was not a cladist. Also, many different disciplines of Biologists use cladistics as a valid methodology, not just Palentologists. Zoologists, Molecular Biologists, Botanists and Paleobotanists, etc. use cladistics. The notion that it is a method which gives bad results must be taken in context - that the alternative methods give far worse results. The sentence cited above is a bit garbled, but there is nothing wrong with pointing out which side of an argument is supported by an overwhelming preponderance of evidence, and which is more a matter of a priori assertion. Should we point out that not everyone believes that the Earth is round, or that some people believe that the Sun orbits the Earth? Sure, the "evidence" supports the "theory" that the earth is spherical, but opinion is not unanimous on that.Jbrougham (talk) 16:28, 31 January 2008 (UTC)

I didn't intend to start a dialogue. My point was simply that generalizations are risky. Stating that older paleontologists cannot be cladists is potentially irksome. Nor is there any requirement that all younger paleontologists be cladists. I happen to be a cladist--but keeping in mind at all times its important limitations. Really, cladistics as a methodology borders on being trivial.
As for birds = dinosaurs, it is a very well supported theory, but still just a theory. We cannot directly observe the evolution from dromaeosaur (or whatever) to bird. On the other hand, we can observe the earth from orbit, so it is a proven scientific fact that the earth is round. There is a gradation from guess to hypothesis to theory to scientific fact, and birds=dinosaurs is not quite a fact yet. Thus, it may serve everyone better to present the idea as a very well supported theory. (Tortugadillo (talk) 05:43, 1 February 2008 (UTC))

Well I'm sorry to discuss this with you if you didn't intend to start a dialogue, but that is a risk you took by posting your thoughts on a talk page. As for older paleontologists; the sentence actually says that some paleontlogists of the older generation do not use cladistics. This is reasonable since Hennig's book didn't really get widely read in english until the late 60's. My understanding is that scientists like Larry Martin, who received their training before that, explicitly state that they are not persuaded by cladistics and prefer the phylogenetic methods that predate it. It could be stated more clearly, though.

Second, I wouldn't be so comfortable about scientific fact. This is a big problem in epistemology and in popular opinion. Many Americans dismiss scientific facts as a matter of religious belief. Though the Earth has been observed from space, as you say, there is still a Flat Earth Society that believes that such photographs are hoaxes. To be fair, they believe that the Earth is round, but flat, and not spherical. Only a handful of people have ever observed the curvature of the earth directly, and many others dismiss it for religious reasons. My point here is that it is a difficult issue. If we emphasize the debates within evolutionary theory we actually make evolutionary theory look weak to many readers. If we emphasize the robustness of the consensus in paleo we sound dogmatic. I have taken both opinions in different contexts. My current feeling is that it is best to present all opinions, but be clear and proportionate about how well supported these opinions are relative to one another. In other words, if there is a consensus of 99% of working Biologists and dozens of detailed studies demonstrate a robustly monophyletic Theropoda, and place Aves within Theropoda, then we shouldn't treat Martin's hypotheses like they are equally valid. We should mention them, but not present it like two equal opinions.Jbrougham (talk) 16:26, 1 February 2008 (UTC)

I think Tortugadillo makes some valid points: Dinosaur spents a bit too much space on the dino-bird link; and if some reputable scientists deny that birds are dinos we should report it, although it would be fair to point out that it's a minority opinion. Re the "older generation" of non-cladists, I'm sure we can reword fairly easily. Philcha (talk) 13:46, 21 February 2008 (UTC)
You're a bit late, Philcha; the "older generation" wording has gone extinct from this article. :) J. Spencer (talk) 14:16, 21 February 2008 (UTC)

What is a dinosaur?

At the top of this page, I see the 'Dinosaur' article is one of the Wikipedia's finest. After numerous corrections by my 5-year old granddaughter of my obsolete usage of 'dinosaur', I came here to learn what a dinosaur now is. Before I can learn why Dimetrodon and Plesiosaurus aren't dinosaurs, I'm referred to 'claudistics', then given a hint:

Non-avian dinosaurs can be generally described as terrestrial archosaurs with limbs held erect beneath the body, that existed from the Carnian faunal stage of the Late Triassic to the Maastrichtian stage of the Late Cretaceous.[1]

Let me pose a question: if anyone can read this article, do they need to? My five-year old granddaughter is having trouble with the last sentence. In fact, so am I. Is this barrage of jargon truly necessary, or is it simply a barrier to understanding? Is this an encyclopedia or a review in a scientific journal?

Normally in a natural science, we classify a set of specimens with common properties as a 'thing' and give it a name, such as 'dinosaur'. The properties must meet certain criteria: they must be objective (easily observed or measured, without argument, by all) and they need be natural (distinct properties of the object itself, no distances in centimeters, no theoretical terms such as 'ancestors to birds'). What is a dinosaur?

Having been a geologist, I'm familiar with the second stage above; but, of course, I'd have to be a vertebrate paleontologist to have even heard of the first stage. Had I a proper definition of a dinosaur, I might understand why the above, seemingly arbitrary, presumably biostratigraphic, boundaries were chosen. Discriminating by age is not satisfying, and discriminating by ancestor is simply incorrect. Admittedly, the above is labeled a 'description'; but is it really necessary to chase down 'archosaur' to find a definition and a clear discussion of why this definition was designed to exclude Dimetrodon and Plesiosaurus (and many others)?

Vertebrate paleontology is one of the more organized branches of geology. It can't be in the chaos illustrated in this article. Isn't there an anatomical definition of a dinosaur, and an anatomical distinction between one and 'Dimetrodon & Plesiosarus' that I can explain to my granddaughter? Is there a motivation for the definition, if it exists? Can't this article's jargon be approximated by English, so everyone can understand it? Can't you vertebrate paleontologists just place the link to 'archosaurs' within commas, or just refer other professionals to scientific papers & reviews? With great respect,

Geologist (talk) 18:38, 1 February 2008 (UTC)

Never mind. I've followed some of the links, and I see now that the Wikipedia has taken its motivation from a newer 'Encyclopedia Britannica': to display the state of knowledge we have attained (and our pride in it). I'll go to my local library instead. Thanks, though: impressive articles. Geologist (talk) 18:57, 1 February 2008 (UTC)

Please, don't just eat and run; I don't want this article to be any more difficult than it has to be.
Dinosaurs were anatomically diverse. There certainly are anatomical distinctions between them and other things, and anatomical characteristics shared by all dinosaurs, but not all dinosaurs have the same anatomy. There aren't characteristics that they all had that can be explained simply without getting into anatomical terminology and lots of caveats to the effect that so-and-so didn't have this. The best characteristics have to do with their upright posture, so that is included in the general statement. Not even this is universal, as some early crocodilian relatives also walked upright and were terrestrial (although they came upon this stance from a different angle and had very different hips and ankles from dinosaurs), but they weren't common and so get ignored.
Breaking down the sentence:
"Non-avian dinosaurs" = dinosaurs that are not birds
"terrestrial archosaurs" = archosaurs that did not fly or swim. This is not an a-posteriori definition, that we don't want swimming dinosaurs or flying dinosaurs. It just reflects the fact that nothing out of the set "Dinosaurs" did so.
"limbs held erect beneath the body" = they walked with upright legs, not sprawling legs.
"from the Carnian faunal stage...of the late Cretaceous" = from when they showed up to when they went extinct.
The essential point of the sentence was to establish who, where, and when, so I've now tried to rewrite it to reflect these essential points. I inserted reptiles after archosaur to allow the option of mentally skipping "archosaur" in favor of "reptile" (i.e. if you don't know what "archosaur" is, you can get the context that it's a group of reptiles), put the faunal stages in parentheses to make them less important, and added explanations of why these stages were included. It is admittedly a general sentence; it is not there to establish a definitive definition, but to provide a quick checklist of important attributes - "I've gone back in time - the Time Box says I'm in the Jurassic - there's a land-living reptile - it is not sprawling - it is probably a dinosaur". J. Spencer (talk) 19:19, 1 February 2008 (UTC)

Thank you very much for your long and kind reply. I actually had parsed your description myself, and even your anatomical definition, which I assume was a necessary adjunct to the anatomical properties defining 'archeosaur'. This is all knowledge -- knowledge my granddaughter won't be memorizing for a while; it's not understanding. The understanding of why you defined a dinosaur thus is your secret. What is it?

Let me try and clarify. In mathematics, a definition is a statement that allows you to always determine whether a 'thing' is a named object, no matter how it may appear. This corresponds to your anatomical definitions. A description is supposed to give you a picture of the object in your mind. This was supposed to correspond to your statement above. I suppose my confusion about the picture is why you have delimited 'dinosaur' in this way. This is your unwritten secret. Let me reveal one, to clarify this.

Some chemical petrologists define a gneiss as a metamorphic rock with coarse crystals and no micas. (You can classify things any way you want, so long as you state your definition.) Their secret is that classical thermodynamics allows them to offer a relation among T, p, and some other variables when the rock transformed from a schist to a gneiss. Other geologists define a gneiss as a rock that can have micas, so long as it is banded. Their secret is that the same thermodynamic theory suggests the rock had strength (did deform plastically, like a viscous liquid), and ameliorated annoying shear stress by placing its foliated minerals in bands of easy slippage. Each geologist then examines regions for patterns that might support these hypotheses. These secrets are usually inserted into the description (though I'd be surprised if you find these anywhere in the geological literature).

Though each definition must satisfy the critieria of objective, natural, &c, there are an uncountable number of ways of defining objects. It's the reason dinosaurs are currently defined as they are above that I was looking for. Now, there needn't always be a reason: field geologists use discontinuities in observable or measurable properties to define 'formations'; but these are so clear, that you can bet money there will be important differences in their environments of formation. This is not clear when a dozen anatomical criteria are needed to define a dinosaur. You have a secret. You forgot to tell us what it is.

Oh, BTW, my granddaughter has taught me that nothing that swam or flew was a dinosaur. This is from her school. She had long learned from me that dinosaurs may not be extinct, and I point to birds in the air. (Though I somewhat dishonestly assured her that a dinosaur has never eaten a kitty cat.) Thus far she has seen no contradiction (which surprises me), though I'm slightly worried about the confusion that will ensue when she does - for her teachers are the final authority. This suggests that the Wikipedia is being used by some schools, and some teachers are more confused that I. Perhaps a 'writing down' of that section would enhance understanding (you could create smaller, more technical links for professionals). Perhaps rethinking how 'terrestrial dinosaur' could confuse the average person is really necessary. One could always keep all that's there and just clarify the 'how & why' dinosaurs are related to flying creatures & swimming creatures, fixing both problems at once.

Thank you again. (Look, If it weren't for the popularity of the film 'Jurassic Park', I shouldn't be suggesting this: I'm sure paleontologists love the article. Your section is very finely written, for an advanced audience.) Thanks. Geologist (talk) 19:49, 6 February 2008 (UTC)

The secret of how "dinosaur" is defined scientifically is based on both anatomy and ancestors/descendants. It's a two-step process in modern vertebrate paleontology, where cladistics is the most common method in use for analyzing evolutionary relationships. First, people study the bones of a number of different animals, make lists of the anatomical characteristics, and then run them through a computer program that finds the best relationships between the animals based on their characteristics. Then, they can go through the results and study the clusters. When dinosaurs are included, they make a cluster to the exclusion of everyone else that nicely fits the pre-cladistic scientific understanding of what a dinosaur is (the pop-culture understanding of a dinosaur as any big dead animal has never been reflected in the scientific literature. The scientific understanding of what dinosaur can be applied to has remained stable since the late 1800s; even when dinosaurs were thought to be an unnatural group, the descriptor "dinosaur" was only applied to specific groups). Thus, this cluster is called "Dinosauria".
Now that we have a dinosaur cluster, we can define it. A simple way to define it is by who is in it. For dinosaurs, the names vary, but the basic plot is the same: Dinosaur=all animals descended from the last common ancestor of [an ornithischian or bird-hipped dinosaur] and [a saurischian or lizard-hipped dinosaur]. If an author doesn't want to deal with birds, or wants to be poetic and choose from the first dinosaurs to be named, the ornithischian is Iguanodon and the saurischian is Megalosaurus. If the author wants to include birds, the saurischian is a modern bird like a House Sparrow. It doesn't matter which saurischian is chosen or which ornithischian is chosen, because the set of animals is the same either way. Pterosaurs, plesiosaurs, ichthyosaurs, mosasaurs, Dimetrodon, and woolly mammoths are all outside of this set. J. Spencer (talk) 21:43, 6 February 2008 (UTC)

Thank you very much. I think I understand now. I'm afraid I'm too old to be of the 'pop-culture', but I'm grateful now learn that a woolly mammoth is not a dinosaur. I'm awed by your understanding of such advanced tools as multivariate statistics. Thank you for protecting me earlier from exposure to it. To the point, however, for I need to explain 'dinosaurs' to my granddaughter. Would the following, pop-culture explanation be an affront to a real scientist?

'Paleontologists choose to reserve the term 'dinosaur' only for those Mesozoic reptiles who shared a specific ancestor. This may be simply because one paleontologist long ago started it, or it may be because we have some living today, in the form of birds. Plesiosaurs, pterosaurs, mammoth, & felines, though probably looking similar at the time, have some bones that are not what we call 'dinosaur bones'. It is the similarities in certain groups of bones that make us believe a Mesozoic reptile to have been a descendent of this ancestral reptile, a dinosaur.

'Though paleontologists still disagree on just which bones reveal the family tree of the dinosaurs, they do agree dinosaurs evolved two forms of gait. Some remained walking on principally four legs to graze, possibly leaning back on two to browse. Just as you saw in 'Jurassic Park'. (These they call ornithopods.) These, sadly, died during a meteor impact. Others walked principally on two legs, and these are the scary ones in the movie. (These they call theropods.) However, all but those who became birds also died from the meteor. Paleontologists need only view the pelvis of a dinosaur to determine its gait. (My granddaughter is well educated for her age.)

'Many other Mesozoic creatures that were not dinosaurs, but were small, crawled near the ground, and lay in water, survived the meteor impact. Their ancestors we see all around us.'

Thank you greatly for your help. Geologist (talk) 23:39, 6 February 2008 (UTC)

That's a pretty good introduction for a five-year-old, although she'll quickly grow out of it. Some slight corrections maybe?
  • Plesiosaurs, pterosaurs, mammoth, & felines, though probably looking similar at the time... Mammoths and felines didn't live at the same time as dinosaurs and it's debatable whether they looked similar (I personally don't think they look even remotely similar other than the fact that they all had bones I guess).
  • Though paleontologists still disagree on just which bones reveal the family tree of the dinosaurs... Mmmm... not really anymore...
  • Some remained walking on principally four legs to graze, possibly leaning back on two to browse. Just as you saw in 'Jurassic Park'. (These they call ornithopods.)... Others walked principally on two legs, and these are the scary ones in the movie. (These they call theropods.) However, all but those who became birds also died from the meteor. Paleontologists need only view the pelvis of a dinosaur to determine its gait. Actually, if you are talking about the long-necked Brachiosaurus in the movie, that is actually a sauropod, more closely related to bipedal theropods. The principle split in the dinosaurs is between the ornithischians ("bird-hips") and the saurischians ("lizard-hips"... ironically including birds). But these hip configurations don't always tell us specifically what gait a dinosaur used, they are more useful to determine shared ancestry. Bipedal locomotion was the ancestral state in dinosaurs, while a quadrupedal gait evolved multiple times in multiple lineages. Saurischians included the bipedal (mostly) carnivorous theropods (the line which includes Tyrannosaurus and birds), and the sauropodomorphs, which started out as small bipedal animals like Thecodontosaurus, and ended up as gigantic quadrupeds like Brachiosaurus. In later theropods like Velociraptor, the hip configuration actually changed to look more like the ornithischians, a configuration inherited by the birds (and the reason why the ornithischians are called "bird-hips" in the first place). Within ornithischians you have small, early bipeds like Lesothosaurus and the heterodontosaurids, which came before several groups that independently became quadrupedal. These include the spiky stegosaurs and the armored ankylosaurs, which are related to each other and had small, armored bipedal ancestors like Scutellosaurus; the horned ceratopsians, which include the famous Triceratops and Styracosaurus, but also evolved from smaller bipedal ancestors similar to Psittacosaurus; and the ornithopods, which included a wide variety of animals, from small ones Hypsilophodon to huge ones like Lambeosaurus, most of which could move on either two or four legs, their preference determined largely by their size.
  • If you want to specify to your granddaughter which groups of animals are dinosaurs, you could say something like "the spiky ones like Stegosaurus, the armored ones like Ankylosaurus, the horned ones like Triceratops, the duck-billed ones like Lambeosaurus, the long-necked ones like Brachiosaurus, the two-legged meat-eating ones like Tyrannosaurus and their relatives the birds, and all the other creatures in between that tell us that they are related"
Hope this helps! Sheep81 (talk) 00:23, 7 February 2008 (UTC)
Actually, I wonder if it would be possible to list the major groups of dinosaurs, with an example or two of each, somewhere in the "what is a dinosaur?" section. It would also have to specify that not all dinosaur fit neatly into these groups, however. Sheep81 (talk) 00:46, 7 February 2008 (UTC)

As you were suggesting the relationship between popular dinosaurs be included in the article, I was writing a thank you note and hoping it would be incorporated. Though I still don't know exactly why 'Dinosauria' was chosen as it was (though I'm more than familiar with cluster analysis), the above response is precious to me. (Jack Horner's office was next to mine at Princeton, but I never bothered him about dinosaurs. Vertebrate paleontology was a tiny specialty then, supported by few universities.) Now I regret that my granddaughter knows more than I. The above is wonderful: she has learned the names of dinosaurs, but not their relation to one another. Your note is written in clear English, using jargon only when necessary. Thank you very, very much. Many, I suspect, would like to see something like the above in the 'Dinosaur' article. Geologist (talk) 01:21, 7 February 2008 (UTC)

The first dinosaurs named were Iguanodon, Megalosaurus, Hylaeosaurus, and Cetiosaurus. This was quite a coincidence, as they represented almost all the major groups. Since then, dinosaurs have been (scientifically, if not popularly) understood to include all of these groups (plus the stegosaurus and ceratopsians, included later) and not plesiosaurs, pterosaurs, pelycosaurs, crocodiles, et cetera. I'm not sure why those other groups weren't included, but they never have been. Eventually it realized that all the "dinosaur" groups had erect gaits, while none of the others did, but I don't think this was realized when Dinosauria was first named in the 1840s, when most dinosaurs were known from teeth... another coincidence perhaps. When cladistics took hold in the 80s, saurischians and ornithischians were realized to be more closely related to each other than to any other groups, forming what is called a monophyletic taxon. This taxon needed a name. Since Dinosauria had been commonly used to encompass these same animals since the 1800s, that is the name that got used. Hence Dinosauria = the most recent common ancestor (MRCA) of saurischians and ornithischians and all its descendants. The taxon is real, but it could have been called anything... Ornithiformes, Bigscarybeastia, whatever. So there's no particular reason why that particular name was assigned to that particular group other than historical convention. In fact, the immediate ancestors to dinosaurs (dinosauromorphs and dinosauriforms) look more similar to the most primitive dinosaurs than those early dinosaurs do to Stegosaurus or Struthio. But they are not descendants of the MRCA of Ornithischia and Saurischia so they don't get to be dinosaurs. Them's the breaks, I guess. Sheep81 (talk) 03:04, 7 February 2008 (UTC)
And I figure that if I keep rewriting, eventually I'll get it right. How should "What is a dinosaur?" be rewritten to be more clear? The information about ancestors and descendants is present, but is parked a couple of subsections down. Perhaps it should be rewritten and brought into the beginning of the section? J. Spencer (talk) 04:00, 7 February 2008 (UTC)
I tried a reordering and partial rewrite. Does that help? J. Spencer (talk) 05:11, 7 February 2008 (UTC)
I thought it was good before; it's still better now. The information was there before, you just had to read a bit to get to it. That's fine, but I think it's written more intuitively now. Sheep81 (talk) 05:55, 7 February 2008 (UTC)

This is just a quick thank you to Mr or Ms Sheep for the excellent answer above to my question of why this particular set of Mesozoic reptiles were singled out as one 'taxon' named 'Dinosauria'. The answer apparently lies in the specimens available: the four listed above, Plesiosaurus, Ichthyosaurus, &c. According to the 1911 Britannica, Richard Owen, of England, reclassified all these specimens based strictly upon anatomy. It would seem reasonable that Iguanodon, Megalosaurus, Hylaeosaurus, and Cetiosaurus would be sufficiently similar to be classed together, the class given the name 'dinosaur' (whose meaning is clear from the Greek). This is just a surmise by me, based upon information provided; but it illustrates the sort of historical answer I hoped to find. Thank you very, very much again. Geologist (talk) 06:20, 7 February 2008 (UTC)

Thanks to Spencer for an edit that I shall read soon.

Perhaps this is a good place to remember that (I believe) this is an encyclopedia for the 'pop culture'. It should probably not be scientific literature. Consequently, if ... the pop-culture understanding of a dinosaur as any big dead animal has never been reflected in the scientific literature, then there should be another section in 'Dinosaur' discussing big, dead animals. Words are what different groups of people or different contexts mean them to be. Lexicographers treat language in a descriptive rather than prescriptive manner, and they list the different definitions (what scientists might call definitive descriptions) by number, sorted (usually) by popularity or date of introduction.

This is a real problem when a term such as 'equivalence class' is 'given' to logicians and discussed using only symbolic logic, for this subject is fundamental to classification in every field of study. This shouldn't be a problem with 'dinosaur', but articles not written for a general audience might clarify (in the discussion section) who that particular article was written for. Someone else can then add a section for a different audience (though I'm not sure adding one for the 'pop-culture' described above would be appropriate). These are just opinions by me and may not reflect in any way the Wikipedia's policy.

Thanks again for the fine article. Geologist (talk) 06:20, 7 February 2008 (UTC)

"Consequently, if ... the pop-culture understanding of a dinosaur as any big dead animal has never been reflected in the scientific literature, then there should be another section in 'Dinosaur' discussing big, dead animals"
I disagree. We shouldn't let incorrect popular usage dictate how these terms are used. Otherwise, shouldn't the article Fish have a section discussing whales, since a large number of people today and many more historically think that whales are fish? Not a perfect analogy, but it's a similar case of incorrect popular usage of terms with clear definitions. Dinoguy2 (talk) 06:39, 7 February 2008 (UTC)

Yes, common sense should prevail; or more importantly, the Wikipedia's policy should. However, there should also be a respect for one's audience. If many think whales are fish, the fish article should probably discuss why they are not. Geologist (talk) 06:53, 7 February 2008 (UTC)

Read Spencer's edit. I think it's much clearer than before (to a member of the 'pop culture'). Thanks! Geologist (talk) 06:53, 7 February 2008 (UTC)

Spencer, truly, I don't want to cause any trouble; but, Under phylogenetic taxonomy, dinosaurs are usually defined as all descendants of the most recent common ancestor of Triceratops and modern birds has a severe methodological problem. Definitions must be objective and natural: they cannot contain theoretical terms, such as 'ancestor of'. These theoretical terms are the often the 'secret' that drives the definition; but the definition itself everyone must very clearly agree upon. We can never really know whether a reptile was an ancestor of Triceratops or birds, we can only confidently conclude this, based upon a theory. I'm very sorry to say that your definitions (not descriptions) need to be rephrased. Geologist (talk) 07:16, 7 February 2008 (UTC)

Actually, the... er, definition... of a "definition" in terms of phylogenetic taxonomy requires statements of common ancestry. This is made clear on the phylogenetic taxonomy page, which is linked. We could go into more detail in the dinosaur article, explaining what exactly is meant by "defined" but we don't have to, because we've linked directly to a whole other article explaining the different kinds of definitions in PT. That's the one of the beauties of Wikipedia. Sheep81 (talk) 08:08, 7 February 2008 (UTC)

My bubble has popped. Phylogenetic taxonomy is, as I understand it, the nomenclature of a theory. These definitions are theoretical definitions. The only way, I can see, of stating that a skeleton I see is of an animal that was an ancestor of Triceratops is by going back in time and asking its parents.

I had thought a dinosaur was defined by having certain visible properties on specific bones, decided upon by examining skeletons of four classes of Mesozoic reptiles in the mid 1800s, and clarified in the 1980s by using lots of dots on many pieces of paper. I was happy, because I can do this. I can't go back in time.

What happened to the definition of dinosaur? Spencer went to such great effort to define it caustically. Geologist (talk) 09:54, 7 February 2008 (UTC)

Owen's original definition (basically, big ancient terrestrial reptiles) appears in the first definition section, and in the second section, there is the PT definition, and immediately after that there is the definition as J and I laid it out for you here on the talk page. The third section defines what kind of things are and aren't dinosaurs, and the fourth section provides an anatomical definition of sorts. There are multiple types of definitions, all of which are listed in the article. You can take your pick. PT only allows taxa to be united by shared ancestry, and the term used for the statement of this shared ancestry is "definition"... that may or not be an accurate term according to your concept of a "definition" but that isn't really our call, now is it! We're just reporting what the scientists say. Sheep81 (talk) 10:08, 7 February 2008 (UTC)
Different definitions serve different purposes. There's the quick phylogenetic definition, the technical anatomical definition, the generalized "what does a dinosaur look like and do" definition, the dictionary definition... as a famous Wilbury once stated, "it's all up to what you value." The definition I picked apart is still there, just moved down a couple of paragraphs to put it after the phylogenetic definition. J. Spencer (talk) 14:20, 7 February 2008 (UTC)

OK. I'm good with that. ... actually, I gave some thought in bed as to whether 'dinosaur' or a species itself should be an objective definition or a theoretical definition. ... Dinosaurs did exist, dinosaurs do exist... Indeed, it's your field; you can choose which you want. Once my own ancestry was questioned by someone offended by the existence of dinosaurs. If you make them objects in a theory, you can say 'They did, and they do exist.'  :-) Thank you both for the wonderful discussion. Geologist (talk) 15:44, 7 February 2008 (UTC)

I'm very pleased with the way 'Dinosaur' now reads. Before, I felt that 'terrestrial dinosaur' could be misread by the average person as a description of dinosaurs, as one uses 'cold fish' or 'corrupt politician'; but I wasn't then sure. I've just encountered some evidence of this. Though I had many times amazed my granddaughter by informing her that birds are believed descended from dinosaurs, her pre-school has recently taught her well that 'no dinosaur swam or flew'; so, when I asked her a few minutes ago whether birds could have descended from dinosaurs, see replied 'No! If none flew, that wouldn't be reasonable.' When I suggested that some may have flown, she corrected me, quoting her pre-school teacher. Consequently, I want to thank J. Spencer for his much clearer rewrite and Mr or Ms Sheep for the truly wonderous information and analysis of the primary literature. I could never understand anything well without an historical perspective; but it would appear that the rewrite has corrected a serious, unnoticed problem while it fixed my trivial complaints. Thanks again! (Now her pre-school teachers must re-read the article!) Geologist (talk) 01:43, 10 February 2008 (UTC)

hey how about putting on something about retro-enginiering dinosaurs heard about it from the upcoming discovery channel show "Dinosaurs: Return To Life?" —Preceding unsigned comment added by Aslan10000 (talk • contribs) 23:26, 15 February 2008 (UTC) The whole complaint was about jargon. To put it simply, scientists classify dinosaurs as prehistoric reptiles with legs directly below their bodies that could not swim or fly. Their ancestors were a group of reptiles called Archosaurs. Dinosaurs evolved into birds (see Origin of birds) and that is how they live on today. During the evolution they learnt to fly. Some archosaurs could swim but they did not evolve into dinosaurs. It is probable that no dinosaur has eaten a 'kitty cat', although possibly one's distant ancestor. Thanks, George D. Watson (Dendodge).TalkHelp and assistance 00:53, 18 February 2008 (UTC)

Dendodge suggested "scientists classify dinosaurs as prehistoric reptiles with legs directly below their bodies that could not swim or fly." "Legs below their bodies" includes some non-dino archosaurs, e.g. rauisuchia; "could not swim or fly" makes unwarranted assumptions (how do we know that no dinos swam; if birds are descend from dinos, there may have been an intermediate stage that was anatomically more dino than bird but could fly). The unfortunate fact is that the current scientific definition of "dinosaur" is complex, technical and not entirely free of grey areas. This is an unfortunate by-product of fossil discoveries in the last 10-15 years (before then books aimed at the general public could simply say "dinosaur = archosaur with fully perforate acetabulum, archosaur = diapsid with preorbital fenestra and 4th femoral trochanter" and then quite easily define the technical terms with the help of a few simple images, e.g. acetabulum = hip socket; but now we know that e.g. Saturnalia was a dino which did not have a fully perforate acetabulum). Philcha (talk) 14:10, 21 February 2008 (UTC)
Dendodge is citing a description, not a formal definition, a rule of thumb that would be useful if you found yourself in the Mesozoic and wanted to know what was chasing you. J. Spencer (talk) 14:13, 21 February 2008 (UTC)
If it was chasing me I wouldn't worry about what it was, only about whether I can run faster than you :-) Philcha (talk) 14:46, 21 February 2008 (UTC)

Personal Remark on Definition and Description of Dinosaur

Dendodge's valuable remarks would be slightly amusing if not clarified by Spencer: If a dinosaur were defined by a perforate acetabulum, how could an animal with one non-perforate be a dinosaur? A reading of the articles 'cladistics' and 'species problem' explains how. A reading of these affects the clarity with which 'dinosaur' is defined. The scientific methodology of us who admire the goal of 'unified science' draws heavily from mathematics: a description gives one a picture in one's mind (as Dendodge's does); a definition is often very cryptic, but it offers a test by which any object can be operationally tested to be a 'blip' or not. Clearly, this distinction is not used by biologists or, consequently, paleontologists.
We positivists are very careful to assure our fundamental definitions, such as a rock formation in the field, are both natural (relatively continuous, separated by discontinuities) and operational (we need use only objective observations and measurements). I, at least, was confused why one would define a species with a theory (a theoretical definition) rather than fundamentally (an equivalence class of properties distinguishing a set of specimens as a species or a dinosaur).
Fundamental definitions, however, are easily changed; and a scientific paper can (IMOO) define a granite any way it wishes, so long as the definition is presented there. Making a fundamental object, a taxa, a theoretical rather than objective object may appear distasteful, but there is no reason one can't do this. It may be valuable to do so. Finding that a descendent preceded its ancestor requires an improvement in evolutionary theory rather than a the trivial fix that fundamental objects can be given.
Still, I don't see it necessary to blur fundamental and theoretical, or even objective and subjective, as cladistics does. Theoretical definitions are presumably artifacts of Linneaus, (probably Mendel), and Darwin, though Darwin defined species both ways. This 'inherited' (no pun intended) violation of common methodology hasn't gone unnoticed, in the 'species problem' article. Cladistics is far from objective, ending with a phylogenetic tree. In fact, cladistics is considered by some synonymous with phylogenetics! So, IMO, one can't really answer my original question ('cladistics' just begs the question), drawing a clear distinction between the definition and description of dinosaur, for the definition of 'species' in biology is anything but clear. Geologist (talk) 08:40, 19 March 2008 (UTC)

Consensus on the impact as the cause of dinosaur extinction -- according to whom?

Though the general consensus is that an impact event was the primary cause of dinosaur extinction -- Where was this factoid gleaned? I actually am a palaeontologist and haven't come across anything even remotely akin to a consensus on this issue. There certainly is a consensus that there *was* an impact event, but that it killed off the dinosaurs is a little more difficult to argue. For a start, dinosaur diversity plummeted through the Maastrichtian (22 families at the start, half that in the Late Maastrichtian generally, and nothing at all found exactly at the K/T boundary), so they were dying out anyway. The real question is why that was happening, and this essay seems to side-step that topic entirely. At best you could say the impact bumped off the last of the dinosaurs. But to say the dinosaurs were dying out for the millions of years prior to the K/T boundary because the impact event was going to happen is obviously silly. Cheers. —Preceding unsigned comment added by 82.26.84.115 (talk) 18:06, 13 February 2008 (UTC)

I agree that there is no consensus. I wonder why there was no large extinction of amphibians, despite worldwide acid rainstorms following the impact. And it does appear that dinosaur diversity was dropping off, at least in western North America, the ONLY place that has been well-sampled immediately before K-T. We simply don't have the evidence to say that was happening worldwide. Sheep81 (talk) 20:29, 13 February 2008 (UTC)
I would add that it is strongly (and convincingly) argued that the dropoff in diversity in North America is a sampling problem, and not real. You only have to look at the apparent lack of diversity in the Santonian to see that. I will dig up the relevant literature if necessary, there are plenty of papers arguing this. -- John.Conway (talk) 23:38, 18 February 2008 (UTC)

Okay, the refs:

  • Fastovsky et al., 2004. Shape of Mesozoic dinosaur richness. Geology
  • Archibald et al., 2004 Dinosaur extinction. The Dinosauria.
  • Pearson et al., 2002. Vertebrate biostratigraphy of the Hell Creek Formation in southwestern North Dakota and northwestern Hell Creek Formation and the Cretaceous-Tertiary Boundary
  • Pearson et al., 2001. Palynologically calibrated vertebrate record from North Dakota consistent with abrupt dinosaur extinction. Geology
  • Sheehan, et al., 2000. Dinosaur abundance was not declining in a "3 m gap" at the top of the Hell Creek Formation, Montana and North Dakota. Geology 28(6):523-526.
  • Sheehan, P.M., and D.E. Fastovsky. 1992. Major extinctions of land-dwelling vertebrates at the Cretaceous-Tertiary boundary, eastern Montana. Geology 20: 556-560.
  • Sheehan et al., 1991. Sudden extinction of the dinosaurs: latest Cretaceous, upper Great Plains, USA. Science

—John.Conway (talk) 00:10, 19 February 2008 (UTC)

That isn't a consensus, that's a body of opinion. You'll find another body of opinion (Norm MacLeod, Gerta Keller etc.) who make a very different interpretation of the evidence.
  • Keller, G. & MacLeod, N. (Eds), (1996). Cretaceous-Tertiary Mass Extinctions : Biotic and Environmental Changes. W. W. Norton & Co
  • Williams, M. E. 1994. Catastrophic versus noncatastrophic extinction of the dinosaurs: Testing, falsifiability, and the burden of proof. Journal of Paleontology, 68, 183-190.
Whether or not they're right is another matter, but speaking as a professional palaeontologist I'm perfectly aware that there isn't a consensus. There's a discussion, with good arguments being made on either side, but as yet no conclusion. I'm afraid that wording things otherwise puts the wrong spin on things, telling people who follow dinosaurs as a hobby that palaeontologists have made up their minds. They have not, and are not likely to given the paucity of evidence. Cheers. —Preceding unsigned comment added by 82.26.84.115 (talk) 13:42, 25 February 2008 (UTC)
Mmmm... John's references argue the same position as Keller's and MacLeod's... look at the title of Sheehan 2000 for example. Sheep81 (talk) 05:14, 27 February 2008 (UTC)
Sorry, strike that, got myself backwards. Sheep81 (talk) 05:16, 27 February 2008 (UTC)
Because I became isolated from the literature just before the Caribbean crater was discovered, another geologist should offer a remark here. Geologists, as paleontologists do, see many taxonomic discontinuities (catastrophes) in strata. We look for explanations, explanation which lie in our domain.
Geologists have often reasoned backward, finding a cause before an event. It is very exciting to find a crater the size of the Caribbean's, and contra-coup volcanism is rather attractive. We have to ask: What effect would such an event have upon terrestrial animals? Though I wish a competent geologist would comment on this, the factoid that an impact event was the primary cause of dinosaur extinction is likely the consensus among general geologists, the other 'owners' of extinction events. I have no references, but I strongly suspect many can be found. Geologist (talk) 09:10, 19 March 2008 (UTC)

Opening Paragraph Structure

I feel there is a problem with the line "One group of dinosaurs is known to have survived to the present day: taxonomists believe modern birds are direct descendants of theropod dinosaurs." I really don't care whether someone believes birds are or aren't dinosaurs. But the sentence says they are dinosaurs and they are descended from dinosaurs. Isn't that having it two ways? I've tried to correct it but made no headway so please someone else straighten it out. Right now you could substitute the sentence "one group of australopithecines survive to the present day: taxonomists believe modern Homo Sapiens are direct descendants of australopithecines." That sentence would be wrongly worded as is the present statement on dinosaurs. Keep it either they are dinosaurs, or they are descended from dinosaurs... Being so cladistic is very confusing to someone reading this article and is really ridiculous. You'll almost have to erase the word extinct from the dictionary. Fyunck(click) (talk) 07:58, 17 February 2008 (UTC)

I'm not seeing the problem. We are humans, our parents are humans, therefore we descended from humans but still are humans, right? I'd suggest just removing "dinosaurs" from after "theropod" to make theropod a noun instead of an adjective, but it's still the same thing under your concern, as birds are theropods and the descendants of Mesozoic theropods. Birds are a type of dinosaur. Birds descended from X group of dinosaurs. Now what? J. Spencer (talk) 16:08, 17 February 2008 (UTC)
It's a big problem when I hear students having problems with this site. That's why I poked around here. There are plenty of wiki and publications that say dinosaurs became extinct 65 million years ago. There are plenty of wiki and publications that say birds are likely (or are) descended from dinosaurs. There are more recently wiki and publications that say birds are dinosaurs. But only in this encyclopedia do I see birds are dinosaurs and birds are descended from dinosaurs in the SAME sentence. That is extremely confusing for most people except for the most extreme cladistic interpreters. Plus this very article specfically states that it will always use "dinosaur" as a synonym for "non-avian dinosaur". So again that sentence makes no sense. You also have "known" and "believe" in that sentence to further confuse people on its validaty. It's a mess. I can do a little more tweaking and change it again but it would sure be better if someone more in tune with dinosaurs (preferably a scientist here) would correct it to make it readable for everyone...not just someone with expertise in cladograms. Fyunck(click) (talk) 04:42, 18 February 2008 (UTC)
Well, how is it now? J. Spencer (talk) 05:01, 18 February 2008 (UTC)
It looks wonderful. And whether you use "most likely" or "are" is something for paleontologists not me. I just wanted clarity in that sentence and you provided it. Thank you. Fyunck(click) (talk) 06:38, 18 February 2008 (UTC)
Lots of good comments above, although i haven't read most of them---too verbose. There are still lots of problems with the opening paragraph, though, as well as with the rest of the text. The information is there, but it needs to be proofread by a writer. The opening paragraph, in particular, is crucial. It needs to be eloquent, not awkward, and it needs to draw readers in (if Wikipedia is to be worth anything). Maybe I'll get around to it one of these days. —Preceding unsigned comment added by Tortugadillo (talk • contribs) 01:52, 21 February 2008 (UTC)
I agree, most of the sentences do not have a clearly defined objective. I've rephrased it. Philcha (talk) 15:13, 21 February 2008 (UTC)

Archosaurs ≠ Reptiles

This article refers to birds as reptiles, particularly in the section describing diapsids versus anapsids. To say that birds are archosaurs is in line with modern classification schemes, but as "reptiles" is a polyphyletic classification, to say that birds are reptiles is more controversial than saying birds are archosaurs, or even that birds are dinosaurs. Minor revisions could solve the problem. Trashbird1240 (talk) 22:24, 18 February 2008 (UTC)

In which section - you mean in "Classification"? It depends how you define "reptile" - if "reptiles" = sauropsida, there's no problem. Technically "sauropsida" would be more accurate, but this article does not and IMO should not go all the way back to basal amniotes, so I think it's OK to assume "reptiles" = sauropsida and there's no need to burden readers with another technical term (of which the article contains enough anyway). Philcha (talk) 15:28, 21 February 2008 (UTC)

What is a dinosaur?

I think this whole section is poorly structured:

  • "Original definition" is fine as is.
  • The first sub-section ("Modern definition") makes the unstated assumption that dinos are monophyletic.
  • "Distinguishing features" is fine except that the final para, about erect limbs, belongs in "General description" (therian mammals have erect limbs, using a similar but convergently evolved mechanism; rauisuchia also had erect limbs, using a different mechanism).
  • "General description" has been used as a dumping ground for snippets that are interesting but do not form a coherent whole.

I think the phylogenetic definition should follow "Distinguishing features". Whether "General description" should be the 2nd or 4th sub-section of "What is a dinosaur?" depends on whether one wants the article to feel as if it's aimed at "non-technical" or "technical" readers. Personally I prefer the "non-technical" approach with "General description" coming 2nd, before "Distinguishing features". Philcha (talk) 16:02, 21 February 2008 (UTC)

I suggest the following order of items in "General description":

  • Hard to provide a single general description, considering the diversity of dinosaurs that appeared during their 160M years (excluding birds).
  • All had erect hindlimbs (note "hindlimbs" - bipedal origins only implies erect hindlimbs, and there's still argument about ceratopsian forelimbs, see Dino Mailing List: Triceratops running speed)
  • All early dinos were bipeds; even the largest predators remained bipeds, although the very largest dinos (all vegetarian) were quadrupeds. The bipedal dinos stood and walked with their backbones horizontal and their body weight balanced over the hindlegs by a heavy tail (use images from Tyrannosaurus to show correct and incorrect posture).
  • Initially looked like bipedal reptiles with long legs and short, fairly rigid backs. But later some non-bird dinos had feathers.
  • Diversity of dinos.
  • Things that were not dinos. Philcha (talk) 16:02, 21 February 2008 (UTC)
You know, I hate dragging this up, (as I have in the past, and then shut up), but the current scientific consensus and usage of "dinosaur" the scientific liturature does refer to a monophyletic group that includes birds. Trying to come up with a non-technical definition (which is paraphyletic) is getting close to original research. Creating lists of "dinosaurian" features also reinforces the all-pervasive, and completely wrong, notion that current biological classification is based on features rather than phylogeny.

—John.Conway (talk) 18:34, 21 February 2008 (UTC)

I am not disputing that monophyly is the current consensus. But that consensus is not some political pact, it's based on the evidence of shared derived characters, and that evidence should be presented in the article before a definition that simply assumes monophyly. And which part of my suggestion did you think was "getting close to original research"? Philcha (talk) 22:03, 21 February 2008 (UTC)
No, the current definitions in use in the literature define dinosaurs as being monophyletic - they can't be anything else. It is getting close to original research to find a bunch of characteristics and present them as if they are a definition. That is not what is done in the literature, and indeed is contrary to the actual definition in use. — John.Conway (talk) 13:04, 23 February 2008 (UTC)
The current definitions would be blown sky-high if cladistic analysis indicated polyphyly. This is not a fanciful notion, as polyphyly was the consensus view for a long time (see refs in article). The current definitions are merely a convenient way of summarizing the range of animals which current cladistic analyses group together. Evidence comes first! Philcha (talk) 10:56, 28 February 2008 (UTC)
'Evidence comes first!' Whoa, a philosopher! When I was confused by the definition of a dinosaur, I had indeed expected to see the all-pervading natural, positivist definition based upon properties of bones partitioned into equivalence classes (claudistic definition). Phylogeny is what we 'old-fashioned' geologists might call 'theory'. It was my illusion that, as John Conway remarks, everyone thought like me. Upon writing a biologist, I discovered that zoologists, too, 'define' species phylogenetically (if that's a word).
There are petrologists who define metamorphic rocks by their temperatures of equilibration (in fact, the IUGC does), what I would instead call a description based upon thermodynamic theory. Whether there are any biologists who switch definition and description I don't know, but whether I think phylogenetic definitions to be unscientific is irrelevant: if all biologists clearly base definitions on phylogeny, that should be made very clear; for, If I might delicately point out, it is a very surprising fact.Geologist (talk) 01:57, 17 March 2008 (UTC)
Can we please not call dinosaurs reptiles? JPotter (talk) 08:57, 17 March 2008 (UTC)
"For the sake of monophyly", we'd better, or Reptilia becomes paraphyletic! ;) Dinoguy2 (talk) 12:08, 17 March 2008 (UTC)
It always is a mix of excitement and melancholy when you return to an article after a long break to find a lot of great new editors, great new prose, and great missing prose. I had a great footnote on why a dinosaur is not a reptile, I wonder what happened to it? At least my section of the cladistic definition of a dinosaur is still in tact, for the most part, although it's changed quite a bit and the reference is missing. It was a really great reference too. JPotter (talk) 19:10, 17 March 2008 (UTC)
Curious- in what way is a dinosaur not a reptile? I can't figure out how this would go under either traditional or phylo taxonomy, unless you're using Bakker's Class Archosauria or Paul's (whatever class Paul erected in PTW). Dinoguy2 (talk) 21:13, 17 March 2008 (UTC)
I think the term "reptile" has fallen out of use in evolutionary science because it's so ambiguous, e.g. : (a) = amniote, in which case all synapsids are "mammal-like reptiles", including us; (b) = sauropsid, in which case birds are reptiles, amniotes are amniotes and synapsids are synapsids. Most narrower meanings are paraphyletic, as they would exclude birds but include the common ancestor of birds and other sauropsids. Philcha (talk) 23:58, 17 March 2008 (UTC)
Indeed. Actually, if we are going to call dinosaurs reptiles can we at least put a footnote attached to reptile like I had before. I'll try to dig it up. JPotter (talk) 07:07, 18 March 2008 (UTC)
Here's the diff [[1]] JPotter (talk) 07:20, 18 March 2008 (UTC)
PHY

This User Believes All Taxa Should be Monophyletic

I agree with the sentiments, but I don't think the intro is the place for so much detail. Perhaps in the section about classification? Philcha (talk) 09:08, 19 March 2008 (UTC)
Saying dinosaurs are reptile-like is more confusing to the average person who doesn't know a lick about phylogenetic nomenclature, and even to some who do, seeing as how many scientists continue to use a monophyletic clade Reptilia with about the same definition usually put forward for Sauropsida.[2] And, if you want to be truely monophyletic, saying they're bird-like is also misleading. Exactly how bird-like are birds anyway? ;) This user, in the interest of full disclosure, doesn't get what's so bad about paraphyletic groups in taxonomy, which is the art of dividing life up artificially no matter how you try to disguise it. Dinoguy2 (talk) 12:03, 18 March 2008 (UTC)
How about trying to divide up life non-artificially? JPotter (talk) 17:41, 18 March 2008 (UTC)
Can't be done, except maybe by naming populations, but those tend to be pretty fluid too. Dinoguy2 (talk) 20:59, 18 March 2008 (UTC)
I don't want to get into a cladism vs. linnean systematics debate, all i'm looking for is a brief footnote similar to the one I had in 05. Also, remember, we're writing at a tertiary level here, I don't want to do what Discovery channel does and dumb something down so far that it's inaccurate. Thanks, JPotter (talk) 22:17, 18 March 2008 (UTC)
"... taxonomy, which is the art of dividing life up artificially no matter how you try to disguise it." At the most detailed level there's the Species problem, especially clines / "ring species", but paleontology can't go into that level of detail because we can't observe fossils' mating preferences :-) Philcha (talk) 09:08, 19 March 2008 (UTC)

Intro

A little while ago I edited the intro ([3]) in response to a reader's comment (earlier in this Talk page) that the intro was unclear. Since then someone has inserted into the intro quite a lot (proportionately) of material about dino classification. I think this is too much for an intro and propose to simplify similar to my earlier edit (link above), plus the fact the views on dino matabolism have changed since about 1970 (i.e. I'd remove the classification stuff from the intro). Philcha (talk) 11:07, 28 February 2008 (UTC)

Done. I've kept separate the paras about the dino-bird-croc relationships and dino metabolism, but pointed out that the actual research overlapped. Philcha (talk) 20:39, 14 March 2008 (UTC)

Some suggestions

Hi, I'm from the German Wikipedia, and I'm working on our Dinosaur article. We translate a lot of things from the Englisch WP into German. While checking some text of your Dinosaur article, I found a few things that could be improved:

  • There is this sentence in the behavior section: Trackways have also confirmed parental behavior among sauropods and ornithopods from the Isle of Skye in northwestern Scotland. Your reference (bbc news) only says that such ornithopod-prints where found. It does not say anything about sauropods. You should delete this "among sauropods", or give an other reference. I doubt that this is true.
  • This sentence in the behavior section: and others kept their young in the middle of the herd for defense according to trackways at Davenport Ranch, Texas. This idea seems to be disproved. I read in this book (The Sauropods: Evolution and Paleobiology, page 276) that there is actually no evidence for a strategic herd structure in sauropod dinosaurs and that the theory with such a structure in the Davenport Ranch tracks was disproved by Lockley 1991 in his book Tracking Dinosaurs.
  • This sentence in the behavior section: There is also evidence that other Cretaceous-era dinosaurs, like Patagonian titanosaurian sauropods (1997 discovery), had similar nesting behaviors (parental care). Your reference for this is outdated. There is a new article in this book (The Sauropods: Evolution and Paleobiology, page 298), written by mostly the same authors, who had done a lot of research in Auca Mahuevo, a big titanosaur nesting site in Patagonia. They say that there was a gregarious nesting behavior, but they say that there was little or no parental care in sauropods.
  • This words in the largest and smallest section: 40 meters (130 ft) long Supersaurus. Where do you got the information, that Supersaurus was 40 meters long? Your Supersaurus article says that it was only 35 meters long, and Carpenter says that it was only 30 meters long. (Carpenter, Kenneth (2006). "Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus", Paleontology and Geology of the Upper Jurassic Morrison Formation).
  • You didn't say nothing about the reasons why dinosaurs were so big. Maybee you should add one or too common hypothesis? I think everybody is asking this question to himself while reading the section about the biggest dinosaurs.

I hope this helps you. Bye, --Jens Lallensack (talk) 20:26, 22 March 2008 (UTC)

How's it look now? For why so large, I only had a good ref for sauropods, so that's all I did in that case. J. Spencer (talk) 22:13, 22 March 2008 (UTC)
Great, thanks. I don't know an other ref for why so large, too ... But the theory, that sauropods lived only in dry environments, is maybee not accepted from other palaeontologists. See The Dinosauria (2004), page 315: They listed a lot of Formations in witch sauropods are found in wet conditions, and they say, that sauropods lived in general in mesic conditions and the Morrison-Formation seems to be the exeption. But on the other hand, Carpenter is a big paleontologist, and he knows better than we do. Bye, --Jens Lallensack (talk) 11:29, 23 March 2008 (UTC)
Well, it's not just *dry*, but seasonally dry as well, which is pretty close to mesic. That's my reading, anyway. J. Spencer (talk) 13:19, 23 March 2008 (UTC)

Heat Wave

Some scientists propose that the meteorite caused a long and unnatural drop in Earth's atmospheric temperature, while others claim that it would have instead created an unusual heat wave.[4] —Preceding unsigned comment added by Rdailey1 (talk • contribs) 02:44, 1 April 2008 (UTC) Although the speed of extinction cannot be deduced from the fossil record alone, various models suggest that the extinction was extremely rapid? —Preceding unsigned comment added by Rdailey1 (talk • contribs) 02:47, 1 April 2008 (UTC)

When the comet/asteroid collided with the Earth, The ejecta (bits of rock thrown out of the resulting crater by the impact) re-entered the atmospere and heated global temperatures to very high levels. Next, the temperatures would cool down. Add to this total global darkness for the first few months after the impact, And you've got an extinction event. Most larger animals would die in the heatwave, and the smaller dinosaurs (and other small animals) would die off from the cold temperatures. The Drop in temperature came after a heatwave. T.Neo (talk contribs) 19:29, 29 April 2008 (UTC)

Just a reminder that evidence be used to qualify one's conclusions. (Despite a cliché to the contrary, in science, facts never speak for themselves.) There is very strong evidence for an impact and the energy released; but the details of its effects need be qualified by assumptions written into computer models. Geologist (talk) 01:42, 30 April 2008 (UTC)

Intro may be getting too long?

Hey folks, I was a primary maintainer of the dinosaur article for a couple of years but have not had enough time to work on it much of late...

First, the article is looking good these days! I really like the reworked structure that has been implemented over the past few months. I'm a little concerned, however, that the intro section is getting long and unwieldy. If you look back at versions from, say, 8 months ago, the intro overview was nice and short. I think we should strive to get back to an intro section that's no longer than about 10 sentences / 2 or 3 paragraphs in length. Killdevil (talk) 15:03, 4 April 2008 (UTC)

Well, I always save the lead for last so I can see what it should reflect, but I'm open to suggestions. J. Spencer (talk) 19:47, 4 April 2008 (UTC)
Dinosaur's intro has more paras but fewer words and less screen area than the intro of the old version of Genetics which Wikipedia:Lead section#Length cites as a good example, and the whole of that old version of Genetics is a lot shorter than Dinosaur.
I've just compared the current version of Dinosaur with the version as at 00:21, 26 September 2007. I would be uncomfortable if the intro got much longer, but I think it currently covers what needs to covered. All of these points are covered in greater detail below, so the intro simply summarises the content.
The next question is whether the intro can cover these points more concisely. The first sentence (about Archaeopteryx) of the 2nd para (archosaurs -> dinos -> birds) could be removed without causing problems. I'm struggling to see more concise ways of phrasing the rest. Any ideas?Philcha (talk) 00:56, 15 April 2008 (UTC)

Dinosaurs and their "always in the air tails" in artwork

It seems this generation has been exposed to something I like to call the Jurassic Park fallacy. Ignited by an original study of the Iguana, the fallacy has been taught that dinosaurs spend the day with their tail in the air... since that is how the Iguana ambulates. And, while this may be true in a sprint or run, ( Thulborn 1990) the assumption they did this at rest is probably in error. While studying modern creatures can indeed unlock clue's to the origin of species, one little fact of math is being overlooked. The square of the area. Simply put, a 1x1 size tail, that weighs a unit of 1, requires 1 unit of energy to lift. But, as the tail gets larger.. say 2x2.. now requires a unit of 4 to lift. And a 3x3 requires a unit of 9 to lift. As the tail grows larger, the required energy to lift it increases exponentially. So, basing the behavior on a 2 ounce iguana, and extrapolating to a multi ton creature stretches scientific credibility, and basic math. Every time I see artwork depicting a sauropod munching on a tree, with all 40 feet of its tail in the air while it is at rest, I ponder this contradiction. One should consider that Thulborn was studying a *stampede*, in his 1990 work. And while even a Crocodile lifts is tail during a -sprint-, when at rest, the tail is lowered (or floating) such that it doesn't consume energy. Pop culture, I fear , may have extrapolated a little too much, giving this generation a creature that would expend an enormous amount of energy keeping a 4 ton tail hoisted skyward. The bias in the data, being relatively few tail tracks have ever been discovered, may simply relate to the nature of the terrain where such soft impressions remained for time to discover.. soft and -muddy-, almost exclusively. A cross examination of species with tails that walk in mud, demonstrates that many raise their tails out of the harms way, and still others more saurian in nature, -float- it at the surface. The marks that survive time are -rarely- surface marks. In many ways this is similar to the seeming contradiction that the manus (front) prints of sauropods show well preserved elephant like marks with 5 -blunt- peg-like digits, -conclusively-, yet actual fossils demonstrate there was a large pointed claw, just as conclusively. One theory holds that they held it aloft at all times, and another, that it was retractable. In matters of evolution, the math of energy enters into the equation. Mother nature rarely expends energy that does not provide an advantage, at least not for long. Ergo, all things being equal, Occams razor probably applies. The larger, thicker and heavier a tail, the more likely it was lowered at rest. And conversely, the lighter, more "whip like" the form of tail is evidence of a "high energy", or active, tail. In nature, conservation of energy counts. This holds true from the full spectrum from the small high energy Gecko, the Iguana, to the Komodo dragon, and even the Large African Crocodile. It's simple math at work in the art of evolution. The more mass, the greater the energy required to mobilize it.( F = ma ). Basic Physics. —Preceding unsigned comment added by 24.208.215.251 (talk) 17:09, 4 April 2008 (UTC)

Many (most?) types of dinosaur would not have needed to expend energy to 'lift' the tails into the air. Unlike modern reptiles, the anatomy of the tail was such that this was the neutral position. To lower the tail, the caudal vertebrae would have to come apart and be disarticulated, as in old museum mounts that tried to force the tails into expected natural positions. It was physically impossible for most dinosaur to lower their tail from the base significantly. Dinoguy2 (talk) 22:33, 4 April 2008 (UTC)
I second Dinoguy2 - animal biomechanics is my specialty, and even superficial observation shows that most bipedal dinosaurs had a center of mass over the hips, meaning that not only could the tail be lifted 'for free', but having such a large, flexible protrusion could allow maneuverability beyond what could be expected for an animal of their size. Dinoguy2 is correct about the articulation, and it should also be noted that ligaments connecting adjacent vertebrae could have borne the load easily and 'for free'. Mokele (talk) 23:26, 4 April 2008 (UTC)

If the legs bore the weight, it wasn't "free" any more than standing, versus sitting is "free". With that said, your "free" is beneficial to balance and -locomotion-, in particular, where it serves as "free" balance. I wasn't arguing that -during- locomotion they raise their tails. I just have doubts that the larger, heavier tails were held aloft during rest, it defies the conservation of energy that molds most creatures. And I don't doubt there are examples of ones that *did* hold them aloft, I just imply that tails used as such, are going to be designed as such, and ergo more streamlined, and the total mass lighter.

And as far as limiting it to bipedal, that may be closer to the truth... I have no doubt that the smaller bipedal ones, such a eoraptor, did exactly that. The tail is designed light, and whip like.. signs of F=Ma at work. But Edmontonia ? I even doubt tenontosaurus... while on the move, I don't have much doubts, but that tail is too large a percentage of the total mass to not be rested, when at rest. I suspect strongly that tenontosaurus rested upon it haunches... or would squat resting its belly and tail on the ground, when at rest. Notice in the bipedal as they get large, that the majority of the mass of the tail is located at a distance from the hip less than the length of the leg, after that, and usually before, the form starts getting whiplike, F=Ma taking over again now that a specialized benefit is solved. This is interestingly true of certain quadrupeds, as well... ( Shantungosaurus, takes this ratio to a fault) but as you progress to more Saurian forms that defy this limit, crocodile.. you get tails that rest more often than not (when on land, aquatic discussion is a segway..). And the bigger the creature, the -square- of the cost of the force, after solving the hip fulcrum problem. The fulcrum problem solved as an Exemplar in the bipeds, reminds me of the little drinking red glass birds that were so popular in the 70's...

Even our original study, Iguana, rests that tail when at rest, which is the majority of the time. Now doesn't it ?

And on a small segway, related, I am looking at a cat right now, certainly a creature the holds it's tail aloft, almost to a fault... (spawning many a joke) but, when it lays down, or sits... so does that tail. (unless it is moody or playful)

Conservation of Energy, Counts.


—Preceding unsigned comment added by 24.208.215.251 (talk) 02:34, 6 April 2008 (UTC)

As Dinoguy said, museum mounts actually had their tails broken in order to get the tails to lay on the ground "properly". I'm thinking specifically of Iguanodon, but there were others as well. Conservation of energy counts for nothing if you literally have to break bones in order to get the tails to reach the ground. Firsfron of Ronchester 05:13, 6 April 2008 (UTC)


Ok, I was trying to be non-technical (what with the "free" stuff), but you seem intent on the details, so here they are.
First, the cost of holding the tail erect while the animal is standing is likely either zero or at least insignificant; in ALL bipeds, the tail was a perfect counterbalance to the torso, so the whole body pivoted at the hips like a see-saw. In both bipeds and quadrupeds, the tails were likely stiffened by interconnecting ligaments which would have held the tail aloft passively, with no energetic cost. At any rate, with passive mechanisms, the cost of holding such a tail aloft would have been utterly inconsequential compared to simply the maintenance costs of maintaining the living tissues of such a structure.
Second, your use of hadrosaurs and an iguanadont as examples leads me to question the depth of your paleontological knowledge: we KNOW that those entire groups constantly kept their tails aloft because in all of those organisms, the tail's huge dorsal and ventral spines were overlaid with a 'wickerwork' of thousands of ossified tendons to stiffen it. It's unlikely those animals could even move their tails *at all* much less lower them during rest.
Third, your lever arm analysis assumes freely-moving parts, which is, as I noted, not the case. Consider holding a pair of full water buckets at arm's length; hard, right? Now imagine you're wearing a helmet, and from each bucket to the helmet is a taught rope. Now all you have to do is keep your arms fully extended, much lower cost. A few more anatomical specializations (ligaments to prevent the arms from buckling, etc), and you'd have a wholly passive structure, requiring no metabolic cost at all.
Fourthly, your comparison to existing reptiles is flawed for a simple reason: height. Most living reptiles have very long tails on very, very short legs. Even the huge sauropods with 50-foot tails had 10-foot legs (5:1) while a more common ratio for a lizard or crocodile would be closer to 20:1 (as for lying down, I doubt this was even possible for the truly huge sauropods). This means that, relatively, a lizard tail needs a much shallower bend in order to rest on the ground, and thus less bending per-vertbra, which ties into Dinoguy2's observation that the vertebral bending for a dinosaur to drag a tail would have been impossible.
So, in summary, dinosaur tails were likely (and in some cases definitely) supported by a network of tendons and ligaments which made the support entirely passive, and their anatomy (both of the vertebrae and the restrictions of such ligaments) severely restricts dorso-ventral bending. Between their inability to substantially lower their tails and the negligible or non-existent metabolic cost of holding such a tail aloft, there's no reason to suspect a dinosaur's tail was in contact with the ground at any time other than when dead. Mokele (talk) 15:42, 6 April 2008 (UTC)
I should like to clarify some initial, anonymous remarks. "...the required energy to lift it increases exponentially." Yes, and the exponent is always 3. That is, if the shape of a tail is held constant, the energy needed to lift it increases with the cube of its length, or is proportional to its mass. (The tiny Iguana's daily food intake need only increase proportionally with its increase in mass - actually less, as the heat loss through its skin increases as the square - not cube - if its length.) Of more interest would be the torque; but we don't lift a log by grabbing the end on the ground and rotating it upward. Museum curators generally don't attempt to lift tails this way; and neither, I suspect, did dinosaurs. If I might be non-technical, dinosaurs' using their heavy tails just to hold them back (while scraping off their skin) seems as implausible to me as Brontosaurus's using its long neck as a snorkel. Geologist (talk) 02:11, 30 April 2008 (UTC)

Status

Well Dinosaurs are extinct aren't they? Σαι ( Talk) 10:46, 12 April 2008 (UTC)

Most paleontologists and zoolgists regard birds as the surviving dinos - see the articles. Philcha (talk) 11:09, 12 April 2008 (UTC)
Per Conservation status at WP:TAXOBOX, conservation status is not to be used for fossil organisms; instead, the |fossil_range element takes over. J. Spencer (talk) 15:34, 12 April 2008 (UTC)
Also, conservation status is for species (think if birds were included: birds run the gamut from extinct to no concern [and fossil, of course], which would make a status box taking birds into account kind of uninformative). J. Spencer (talk) 15:39, 12 April 2008 (UTC)

Featured topic

Hi., i am wondering why the dinosaur FA level article and the various FAs of dinosaur species haven't been nominated for FEATURED TOPIC? I can't think of any topic (except probably the Solar System) having more featured content. Just a thought --192.8.222.82 (talk) 10:52, 15 May 2008 (UTC

Retrieved from "https://en.wikipedia.org/w/index.php?title=Talk:Dinosaur/Archive_8&oldid=1136663468"