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The Ornithopod Thread- Hadrosaurs, iguanodonts and kin

13

Comments

  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    Yes, in fact you see this with ceratopsians too- the juveniles of different genera/species are almost impossible to tell apart until they grow their characteristic horns and ornated frills, and as you surely know, many small, hornless ceratopsian genera have turned out to be juveniles of better known, larger ones (for example, Brachyceratops is know believed to be a juvenile Rubeosaurus- what was formerly known as Styracosaurus ovatus).


  • Moderators, Category Moderators, Science, Health & Environment Moderators, Society & Culture Moderators, Regional Abroad Moderators Posts: 8,301 CMod ✭✭✭✭ Fathom


    Linnaeus wrote: »
    Recently I read an interesting article about the fossil remains of a juvenile crested Hadrosaur (about one year old at the time of death) which had only a tiny, budding bump on his head. This seems to indicate that baby Hadrosaurs of the crested variety probably hatched without the typical protuberance, which would later develop and grow as these dinosaurs matured.
    Adam Khor wrote: »
    Yes, in fact you see this with ceratopsians too- the juveniles of different genera/species are almost impossible to tell apart until they grow their characteristic horns and ornated frills, and as you surely know, many small, hornless ceratopsian genera have turned out to be juveniles of better known, larger ones (for example, Brachyceratops is know believed to be a juvenile Rubeosaurus- what was formerly known as Styracosaurus ovatus).

    Juveniles confounded classification. Fascinating.


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    The experiment had already been done with Parasaurolophus in the 90s.

    https://asunow.asu.edu/20151021-discoveries-how-speak-dinosaur

    Corythosaurus.jpg


  • Moderators, Society & Culture Moderators Posts: 9,458 Mod ✭✭✭✭ Manach


    Very interesting article. One quibble though. AFAIK the atmosphere of those times differed from today's in terms of composition? So should that have been factored into the recreation?


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    Right, higher oxygen levels and all that... good question, I really have no idea


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  • Registered Users Posts: 218 ✭✭ Linnaeus


    Experimentation indicates that, whatever the real purpose of Parasauropholus' tubular crest, this was capable of making a deep trumpet-like sound. I suspect that the hadrosaurs in general developed crests of various dimensions precisely to be able to emit warning cries to their herd. The crests, some palaeontologists have suggested, might also have improved the hadrosaurs' sense of smell, thus giving them another advantage in identifying the presence of approaching predators.

    As hadrosaurs had few effective means of defense, their crests...when present...would therefore probably have served as tools for survival.


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    Indeed, if it had been for visual display only they probably would've had soft-tissue crests, akin to those of Edmontosaurus if new discoveries are to be trusted.
    Such a complex structure as Parasaurolophus' or Corythosaurus' crest had to serve more than one purpose- kind of like with antelope horns today.


  • Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 91,409 Mod ✭✭✭✭ Capt'n Midnight


    Manach wrote: »
    Very interesting article. One quibble though. AFAIK the atmosphere of those times differed from today's in terms of composition? So should that have been factored into the recreation?
    https://en.wikipedia.org/wiki/Speed_of_sound
    The speed of sound in an ideal gas is independent of frequency, but does vary slightly with frequency in a real gas. It is proportional to the square root of the absolute temperature, but is independent of pressure or density for a given ideal gas. The speed of sound in air varies slightly with pressure only because air is not quite an ideal gas.

    If you use Helium or Sulfur Hexafluoride you get different sounds, but more because of the molecular mass. Composition of air shouldn't change sound too much as N2, O2 are close and CO2 isn't a million miles away.

    There's a lot of N2 sequestered in the biosphere.


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor




  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor




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  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor




  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor




  • Moderators, Category Moderators, Science, Health & Environment Moderators, Society & Culture Moderators, Regional Abroad Moderators Posts: 8,301 CMod ✭✭✭✭ Fathom


    Hadrosaur fossil record. Without crest?


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    Seems like it. May have had a soft-tissue crest, however, as has been suggested for Edmontosaurus. Who knows?


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor




  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    By hydrogen sulfide, it appears. These were among the first dinosaurs for which full skeletons were found. (In the picture below, the first ever mounted specimen of Iguanodon).
    https://www.vrt.be/vrtnws/nl/2018/03/09/iguanodons-van-bernissart-stierven-door-giftig-moerasgas/
    Dino_high_19_EN.JPG?itok=ERfIEUy4


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    https://www.tandfonline.com/doi/abs/10.1080/02724634.2017.1398168?journalCode=ujvp20
    (Abstract). 
    Suggests Edmontosaurus was capable of quadrupedal gait from the start, rather than starting as obligate bipeds and becoming quadrupeds later on as had been suggested. 
    (Below, Maiasaura hatchling, probably similar to the new find)
    maiasauraeggWC-58b9a64e5f9b58af5c8557dc.jpg


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    It is called "Choyrodon" and was found in the same place (and is from the same time) as previously known, high-nosed iguanodont Altirhinus. Hmm...

    https://peerj.com/articles/5300/

    fig-2-1x.jpg

    Here's Altirhinus' skull:

    1200px-Altirhinus_kurzanovi.JPG


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    Weewarrasaurus, a new ornithopod from Australia. Known from a piece of opalised jawbone.

    https://www.nationalgeographic.com/science/2018/12/exclusive-sparkly-opal-filled-fossils-reveal-new-dinosaur-species-paleontology/?fbclid=IwAR1RSRXCdzgY-RbT4l85z6OmOans7rYR_Cj-PFf_GZywLQC_wmKKbBILJfk

    Not really sure how it difers from other small Australian ornithopods like Laellynasaura and Fulgurotherium, known also from very fragmentary remains...

    _104643415_r0_0_2501_1528_w1200_h678_fmax.jpg


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    South America is known for its wide variety of sauropods and theropods, but ornithopod finds are a lot more unusual. Here are some recent ones that may help complete the puzzle:

    https://www.sciencedirect.com/science/article/pii/S0195667118303586

    https://www.sciencedirect.com/science/article/pii/S0195667118304506

    It appears South America had its own ornithopod fauna, different from the one found in North America at the same time, although we do know at least kritosaurs (a genus of hadrosaurids) did migrate into South America at some point, with Secernosaurus/Kritosaurus australis being the best known example:

    Hadrosaur_museum.jpg


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  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    https://royaltyrrellmuseum.wpcomstaging.com/2019/06/10/rare-dinosaur-fossils-reveal-new-details-of-prosaurolophus-display-features/?fbclid=IwAR2v-ZhqyrmQglYiJ0sMkd3BmvwhBylcn23239Pu5MzODcq9YycSsDwWTLY

    prosaurolophus-by-julius-csotonyi.jpg?itok=K29YUDEE&c=ef968452b6dfed08c71a4ae5f42ecb31
    “We noticed that the bony crest grew very slowly in Prosaurolophus and remained small, unlike what happened in some duckbills, which rapidly developed a large bony crest,” says lead author Eamon Drysdale, a University of Calgary graduate student. “Instead, rapid changes in the snout as the animal matured suggest that a soft tissue structure may have been associated with the nostrils and used for display. The snout would have been the primary display feature, rather than the large head crest of other duckbills.”

    This new study provides evidence to support the previously-proposed idea of a showy, fleshy snout.

    A skin impression of a juvenile Prosaurolophus dinosaur shows large scales present on the flank of the animal. These scales were also likely present in the adult individuals.

    5-Prosaurolophus-Skin.jpg?resize=676%2C717&ssl=1


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    Fostoria, a new iguanodontian described from Australia.

    Dinosaur finds consisting of more than one bone are very rare in Australia; in this case, several elements were found, belonging to several individuals.

    http://www.sci-news.com/paleontology/fostoria-dhimbangunmal-07265.html

    image_7265_2-Fostoria-dhimbangunmal.jpg


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    This kind of pathology was known only from mammals.

    https://www.nature.com/articles/s41598-019-45101-6

    41598_2019_45101_Fig1_HTML.png?as=webp

    Tenontosaurus is an early Cretaceous, long-tailed ornithopod most famous for being apparently the favored prey of the raptor Deinonychus.

    31-Tenontosaurus-tillettorum_0fe9.jpg


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor




  • Moderators, Category Moderators, Science, Health & Environment Moderators, Society & Culture Moderators, Regional Abroad Moderators Posts: 8,301 CMod ✭✭✭✭ Fathom


    Hadrosaurs had great variety. Differential reproduction?


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    Fathom wrote: »
    Hadrosaurs had great variety. Differential reproduction?

    Actually what I find intriguing about them is that postcranially, most of them look VERY much alike, and the head/crest is about the only thing that allows one to tell them apart. Something similar happens with ceratopsians. In both hadrosaurs and ceratopsians it can be extremely difficult even for paleontologists to determine what genus or species they're looking at unless there's a skull, and juveniles (which are yet to develop their distinctive crests) are even more problematic.

    Although I suppose the same would be true of say, many antelopes if all we had to go by were the bones...


  • Moderators, Category Moderators, Science, Health & Environment Moderators, Society & Culture Moderators, Regional Abroad Moderators Posts: 8,301 CMod ✭✭✭✭ Fathom


    Adam Khor wrote: »
    ... the head/crest is about the only thing that allows one to tell them apart.
    Did one species have a snorkel on the top of its head? For breathing at waterline, with rest of animal below surface?


  • Moderators, Science, Health & Environment Moderators Posts: 5,279 Mod ✭✭✭✭ Adam Khor


    Fathom wrote: »
    Did one species have a snorkel on the top of its head? For breathing at waterline, with rest of animal below surface?

    The snorkel idea was once suggested for Parasaurolophus, perhaps the most iconic of the hadrosaurs (although one relatively rare in the fossil record):

    parasaurolophus-skeleton.jpg

    The idea has long been discarded due to several reasons:

    1. One would expect a snorkel to project more vertically; instead, the crest grows backwards and downwards at the tip.

    2. Not all Parasaurolophus specimens have a long crest; in fact, it has been suggested that only adult males did, whereas females and juveniles had much shorter crests. This strongly suggests a role in courtship and social interaction. If the crest was a snorkel we would expect all Parasaurolophus to have the same equipment.

    3. Most importantly, there is no opening at the tip of the crest. The animal's nasal passages DO go into the crest but it's just a detour; it is currently believed that the crest functioned not just as a visual display but also as a trombone of sorts, amplifying the dinosaur's calls.

    In the 90s, scientists used a computer simulation to calculate how much air a Parasaurolophus would've been able to blow from its lungs, and reconstructed its possible voice. Check it out, it's rather eerie:



    Keep in mind that Parasaurolophus is believed to have prefered more forested areas than other hadrosaurs, so it makes sense that sound would've been an important part of its communication.

    Also worth mentioning that hadrosaurs as a whole are no longer believed to have been semiaquatic, as was once proposed. The idea was that since they had duck-like beaks, they probably dived to feed on aquatic plants, but this has long been disproven; the beaks were only vaguely reminiscent of those of ducks; in life, they were covered by a rather hooked, sharp keratinous cover to crop vegetation, and they had batteries of thousands of tiny teeth to grind hard food. They weren´t feeding on soft water plants.

    Another piece of supposed evidence for their aquatic lifestyle was the fact that a "mummified" hadrosaur was once found which showed what was interpreted to be webbing between its fingers. However, later it was found that this supposed membrane was actually a sort of "mitten" of skin that kept the three central fingers bound tightly together, an adaptation for supporting the animal's weight as it walked on four legs.

    Their tail was also not flexible, but rigid and very heavy, and probably one of their main means of defense against predators (they could use it like a sledghammer to strike a predator ). It was not sinuous and crocodile-like as suggested by early paleontologists.

    So in short, we have no evidence of aquatic or semiaquatic hadrosaurs as of this moment, and absolutely no evidence of any dinosaurs having snorkel-like crests.


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  • Moderators, Category Moderators, Science, Health & Environment Moderators, Society & Culture Moderators, Regional Abroad Moderators Posts: 8,301 CMod ✭✭✭✭ Fathom


    Adam Khor wrote: »
    The snorkel idea was once suggested for Parasaurolophus, perhaps the most iconic of the hadrosaurs (although one relatively rare in the fossil record).

    The idea has long been discarded due to several reasons...

    Good to know. Thanks Adam.


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