Talk:Dinosaur

Where is the citation for dinosaurs first appearing exactly 231.4 million years ago?

The second sentence currently reads "They first appeared during the Triassic period, 231.4 million years ago". If the first appearance is that specific (tenth of a million years) it should have a citation and I cannot find any scientific reference. If it said 230 mya or around 250 mya that would be fine, but given the precision of the date it should have a scientific citation. I found the 231.4 mya number in both 101 Amazing Facts about Dinosaurs and on clearlyexplained.com, but neither of these are sufficient for a citation. Can someone find an original scientific source for that figure?Jss367 (talk) 04:33, 19 February 2016 (UTC)

• According to Marsicano et al. (p. 511), "The transition to communities containing the first dinosaurs occurred in less than a 5-million year interval, based on unambiguous dinosaur body fossils dated to 231.4 Ma from the lower part of the Ischigualasto Formation (21,25)." I don't have access to the sources they cite, but they are:
  21. Martinez RN, et al. (2011) A basal dinosaur from the dawn of the dinosaur era in southwestern Pangaea. Science 331(6014):206–210.
  25. Rogers RR, et al. (1993) The Ischigualasto tetrapod assemblage (Late Triassic, Argentina) and 40Ar/39Ar dating of dinosaur origins. Science 260(5109):794–797. --Macrochelys (talk) 10:05, 19 February 2016 (UTC)
  • The Martinez paper states that "The Ischigualasto Formation, a richly fossiliferous fluvial succession within a Triassic continental rift basin (6, 19), provides a window to faunal dynamics at the dawn of the dinosaur era. To quantify and temporally calibrate faunal abundance in the Ischigualasto Formation, we logged nearly 800 vertebrate specimens and obtained radioisotopic ages that bracket the formation between 231.4 and 225.9 million years ago (Ma) (Fig. 4) (8, 20)." I think 231.4 refers to the maximum value in the range and not necessarily an exactly known value. I don't see any mention of 231.4 mya in the Rogers paper.
  • Also in the Martinez paper, it lists earlier dates for other types of dinosaurs: "The discovery of Eodromaeus, the reinterpretation of Eoraptor as a sauropodomorph, and the faunal record of the Ischigualasto Formation provide additional evidence that, by mid Carnian time (~232 Ma), the earliest dinosaurs had already evolved the most functionally important trophic and locomotor features characterizing ornithischians, sauropodomorphs, and theropods (17, 23)." The citations there are for articles by Paul Sereno, but I cannot find a specified earliest date in either of those articles.
  • I also found this paper:The oldest dinosaur? A Middle Triassic dinosauriform from Tanzania. Sterling J. Nesbitt, Paul M. Barrett, Sarah Werning, Christian A. Sidor, Alan J. Charig, which you can read here: http://rsbl.royalsocietypublishing.org/content/9/1/20120949. The paper is about the Nyasasaurus which is older than 231.4 mya, but perhaps shouldn't be considered a dinosaur. Either way, the authors state "The exact timing of dinosaur origins and the pace of early dinosaur diversification remain unclear", which goes back to my main point that we don't have the precision to say that dinosaurs "first appeared during the Triassic period, 231.4 million years ago". The paper was published in 2012, so it includes the papers you cited.
  • I noticed that the Wikipedia page "Evolution of dinosaurs" starts with "Dinosaurs evolved within a single lineage of archosaurs 232-234 Ma (million years ago)". There are a few different dinosaurs mentioned on that page that predate 231.4 mya, many citing the reference: Weishampel, Dodson & Osmolska, 2004, The Dinosauria. Unfortunately, I don't have the book so I can't pursue this further.
  • Overall, I think my main point stands that we don't have the precision that this page seems to suggest. I recommend that the article state that dinosaurs first appeared around 230 million years ago, or something to that effect.Jss367 (talk) 14:48, 19 February 2016 (UTC)

Note that there is a big difference between a phylogentically calibrated estimate of when the first dinosaurs likely evolved, and the age of the rock formations containing the earliest actual dinosaur fossils. The first will always necessarily be older than the second. I don't really care what date is listed (the maximum result of the radiometric test or a rounded equivalent) but the above arguments sound a little on the OR side. Dinoguy2 (talk) 19:22, 19 February 2016 (UTC)

• • • • That's a good point. I think that's even more reason to express the first appearance with less precision. Would anyone be opposed to changing the second sentence to "They first appeared during the Triassic period, over 230 million years ago ..."? Jss367 (talk) 21:46, 27 February 2016 (UTC)
        • I would suggest something like "The earliest known fossils than can confidently be identified as dinosaurs have been found in rock formations dated to between x and y." Dinoguy2 (talk) 19:26, 29 February 2016 (UTC)
          • Perhaps that is the best way to approach it. Unfortunately, I don't have the expertise to say what the date range should be. It surprises me that it there seems to be resistance to change and in the two months since I've brought this up no one else has had a problem with it. Does anyone else agree that this statement should be clarified or at least that it is not properly cited? Or am I the only one who thinks this should be changed?Jss367 (talk) 10:17, 25 April 2016 (UTC)

Semi-protected edit request on 25 February 2016

There are many spelling errors I will be able to fix them. Loller12 (talk) 22:44, 25 February 2016 (UTC)

Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format. Cannolis (talk) 22:53, 25 February 2016 (UTC)

48% of dinosaurs named aren't really dinosaurs?

Not totally sure about where information from this article [1] I came across should go, but some of its key points should be listed/cited in this article. If this were a history of dinosaurs I'd put it in the "Historiography" section. But this is a science article, so...I believe it useful that appropriate skepticism (in the scientific sense) this article identifies be demonstrated here somewhere...Hires an editor (talk) 12:56, 27 March 2016 (UTC)

Well, two things: This is true for most other taxonomic groups, not only dinosaurs. Taxa are reclassified and synonymised all the time, even living ones. Furthermore, it would be better to cite a study than a pop-science website. FunkMonk (talk) 16:36, 27 March 2016 (UTC)

Also the source does not claim that all these aren't dinosaurs: they are mostly nomina dubia which means they largely are dinosaurs, just not represented by distinctive enough remains; or junior synonyms which are identical to a dinosaur already named. Only 58 names of over a thousand were given to non-dinosaurian fossils.--MWAK (talk) 08:18, 6 April 2016 (UTC)

Semi-protected edit request on 28 April 2016

There is currently the following sentence in the lead paragraph: "Until the late 20th century, all groups were believed to be extinct; however, the fossil record indicates that birds are modern feathered dinosaurs, having evolved from theropod ancestors during the Jurassic Period.[2] As such, birds were the only dinosaurs to survive the mass extinction event.[3]"

No such "belief" existed in the "late 20th century". I went to school in the 1970s and 1980s and we were already taught about the Archaeopteryx ("First Bird") found in the late 19th century and having been thought ever since to be the link between dinosaurs and birds. Furthermore, birds are NOT dinosaurs any more than we are Homo Egaster, nor were there any actual birds in the Jurassic Perios - only bird-like theropods.

Please change the sentence to: "The fossil record indicates that birds are the descendants of dinosaurs, having evolved from theropod ancestors beginning in the Jurassic Period and survived the mass extinction event.[2][3]"

Thanks Krautkontrol (talk) 13:28, 28 April 2016 (UTC)

Not done: please establish a consensus for this alteration before using the {{edit semi-protected}} template. "Dinosaur" is a word like "primate" and covers many species, so calling birds "feathered dinosaurs" (good read!) is by no means inaccurate in my humble opinion. Yes, Archaeopteryx had been around for a long time; however, nobody actually made the deeper connection between modern birds and dinos until the latter part of the 20th. "Late 20th century" can technically cover from 1951 on, and yet would realistically refer to later decades, such as the 70s, 80s and 90s (and the trend to more closely relate birds and dinos began in the 60s). I might also point out that, while modern humans are not †Homo ergaster, we do share the genus Homo and all higher taxa with that extinct species. So with all due respect, in any discussion about making this change, I would probably oppose it based on your argument above.  Stick to sources! Paine  10:15, 30 April 2016 (UTC)

Another point, though Archaeopteryx has been known for a long time, it wasn't necessarily considered a dinosaur (or a descendant of dinosaurs) for most of this time. FunkMonk (talk) 10:31, 30 April 2016 (UTC)

"Non-avian dinosaurs"

This term has gathered currency recently, with much in the way of definition or explanation, notably in Wikipedia. The term "non-avian dinosaurs" suggests that avians, or birds are actually dinosaurs ("thunder lizards"), rather than descended from dinosaurs. Kortoso (talk) 18:17, 4 May 2016 (UTC)

both true: birds are dinosaurs, and descended from dinosaurs (otherwise, the term "birds" would be synonymous with the term "dinosaurs") HMallison (talk) 20:58, 4 May 2016 (UTC)