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The Ornithopod Thread- Hadrosaurs, iguanodonts and kin

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


    Strontium isotopes reveal migratory behavior of late Cretaceous hadrosaurs:

    https://royalsocietypublishing.org/doi/pdf/10.1098/rsbl.2019.0930
    Dinosaur migration patterns are very difficult to determine, often relying solely on the geographical distribution of fossils. Unfortunately, it is generally not possible to determine if a fossil taxon's geographical distribution is the result of migration or simply a wide distribution. Whereas some attempts have been made to use isotopic systems to determine migratory patterns in dinosaurs, these methods have yet to achieve wider usage in the study of dinosaur ecology. Here, we have used strontium isotope ratios from fossil enamel to reconstruct the movements of an individual hadrosaur from Dinosaur Provincial Park in Alberta, Canada. Results from this study are consistent with a range or migratory pattern between Dinosaur Provincial Park and a contemporaneous locality in the South Saskatchewan River area, Alberta, Canada. This represents a minimum distance of approximately 80 km, which is consistent with migrations seen in modern elephants. These results suggest the continent-wide distribution of some hadrosaur species in the Late Cretaceous of North America is not the result of extremely long-range migratory behaviours.

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


    More on the cells and cartilage traces supposedly found in Hypacrosaurus remains (naturally some paleontologists are skeptical, as they were with the T. rex soft tissue a few years ago).

    https://gizmodo.com/paleontologists-are-skeptical-about-baby-dinosaur-cells-1842034627

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


    "New" Arctic hadrosaurs turn out to be Edmontosaurus after all.

    https://phys.org/news/2020-05-arctic-edmontosaurus-caribou-cretaceous.html

    The so called "Ugrunaaluk" was described in 2015. It appears now that it's just Edmontosaurus (aka Anatosaurus aka Anatotitan aka Trachodon), the same duckbilled dinosaur that coexisted with (and was preyed on by) Tyrannosaurus rex further south.

    Edmontosaurus thus becomes one of the most widespread hadrosaurs known, especially if other very similar hadrosaurs from Asia turn out to be part of this genus as well.

    It was also one of the largest, with some North American specimens reaching up to 12 or maybe even 15 m long, and Asian ones potentially even larger ("Shantungosaurus" , which may well be an Asian Edmontosaurus).

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


    Like modern reptiles, hadrosaurs did not have intervertebral discs, suggests study on T. rex bitten specimen:

    https://onlinelibrary.wiley.com/doi/10.1111/ahe.12573
    The flat‐end surfaces of dinosaur vertebral centra led to the presumption that intervertebral discs occupied the space between their vertebrae. A set of fused hadrosaur vertebrae allowed that hypothesis to be tested. The Tyrannosaurus rex responsible for this pathology did not escape unscathed. It left behind a tooth crown that had fractured. Fragments of that tooth were scattered through the intervertebral space, evidencing that there was no solid structure to impede its movement. That eliminates the possibility of an intervertebral disc and instead proves the presence of an articular space, similar to that in modern reptiles, but at variance to what is noted in birds. While avian cervical vertebral centra appear to be separated by diarthrodial joints, the preponderance of their thoracic vertebral centra is not separated by synovial joints.

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


    Early Cretaceous ornithopods found in China, described as new species Changmiania liaoningensis. Changmian means "eternal sleep" in Chinese, as the creatures were apparently preserved by volcanic ash while sleeping inside their burrow. The animal shows adaptations to a fossorial (burrowing) lifestyle including a shovel-shaped nose and thick, powerful neck and shoulders. This adds to the growing evidence that small ornithischians were often living in burrows.

    The animal appears to be a most primitive form of ornithopod despite being contemporary with Iguanodon.

    https://www.naturalsciences.be/en/news/item/19274

    News_Changmiania_Sleeping%20beauty_Carine_Ciselet_EN.jpg?itok=0CrzeZHy


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


    Ajnabia, the very first hadrosaur from Africa, discovered in Morocco. The morphology suggests it was a lambeosaurine (crested duckbill) related to the ones found in Spain such as Arenysaurus.


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    https://www.nicklongrich.com/blog/ajnabia-odysseus-the-first-duckbill-dinosaur-from-africa?fbclid=IwAR07-Y_rzgrGHGf9EutpFh6e-17sr8719u3frVNTyUd9reQcW6fRjUk9gg4

    The author suggests that, in the absence of land bridges, hadrosaur may have swam or floated across the sea to colonize continents- not just Africa but South America too.


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


    Fathom wrote: »
    Floated across Bering Strait to North America. Then migrated south? Or island hopped east across south Pacific? Kon-Tiki hadrosaurs?


    Unsure about continental drift 65 million plus years ago.


    Asia and North America were connected by land (the so called Beringian land bridge) for most of the Cretaceous; dinosaurs would've walked from one continent to the other.

    On the other hand, there's no evidence thus far of a land bridge between North and South America at the time. Hadrosaur remains are very common in Mexico, however, including those of Kritosaurus (the South American hadrosaurs are very much like Kritosaurus, with the better known being Kritosaurus australis (=Secernosaurus?), so they probably did island-hop, swim or float to South America from what is today Mexico.


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


    Fathom wrote: »
    Higher ocean levels? Smaller polar caps? Wonders if the same will occur with continued global warming?

    Yes, around 250 m higher than today's sea levels, on average, IIRC.

    Here's National Geographic's take on what the world is heading to if the current global warming trend continues. You can see Central America becomes practically a chain of islands- eventually, both Americas could indeed become isolated again.

    Interesting to see that the Amazon would again be connected to the Atlantic, as it was originally back in the days of the giant caiman Purussaurus.

    https://www.nationalgeographic.com/magazine/2013/09/rising-seas-ice-melt-new-shoreline-maps/


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


    Fathom wrote: »
    Would hadrosaurs float without the aid of swimming? Then move their legs and tail to navigate?

    I would imagine they'd use their legs when swimming, but they really weren´t made for it so to speak- the idea of aquatic hadrosaurs has long been out of favor.

    The hadrosaur tail was very rigid, held stiff by special ossified tendons. This made the tail useful for counterbalance and maybe for defense, but it was not flexible enough to aid in swimming like that of a lizard or a crocodile.

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


    Famous hadrosaur Parasaurolophus reexamined. The paper includes an analysis not only of the Parasaurolophus holotype but also of the animal's portrayals in paleoart throughout the years. The most interesting find is that the "saddle" or kink on the anterior spine of the holotype is actually a pathological feature, likely caused by a heavy object, possibly a tree, that fell on top of the animal at some point.

    https://onlinelibrary.wiley.com/doi/full/10.1111/joa.13363#.X9M5wOqaeOY.twitter

    joa13363-fig-0006-m.png


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


    You mean prolific as a group, as in speciose, or prolific regarding the number of eggs they lay?

    The key to their success as a group has often been suggested to be their masticatory apparatus, which was pretty sophisticated for a reptile. They had "dental batteries" consisting of many rows of teeth (hundreds of them) which were constantly being worn down and replaced, a little bit like shark teeth (except instead of falling out they'd be reabsorbed when worn out and new ones would erupt to occupy their place). This ensured that hadrosaurs were never left toothless (unlike say, elephants, which have only six sets of molars during their lives and often die of starvation once they have worn the last one).

    battery.jpg

    The dental batteries functioned as a grinding surface, like a mammal's molars, allowing them to process hard, fibrous plant material that other dinosaurs could not eat (most plant-eating dinosaurs either had very simple masticatory capabilities, or none at all, using their beak or front teeth to crop vegetation and basically swallowing it whole).

    This would have allowed hadrosaurs to feed on a wide array of foods and fill ecological niches with very little competition. Another advantage they had was their large size and the ability to stand on their hind legs to reach food located at 4 m above ground or more, again minimizing competition with other dinosaurs (the golden age of hadrosaurs was the late Cretaceous, when sauropods had become rare in the Northern Hemisphere. Perhaps it is no coincidence that hadrosaurs, although certainly present in South America, for example, never became as abundant and speciose as they did in the north; sauropods were very much still in business in the southern hemisphere all the way to the KT extinction).

    As for why they lay so many eggs, I'd imagine for the same reasons ostriches, crocodiles and turtles do- to increase chances of survival of at least some of the clutch. Baby hadrosaurs also grew very rapidly to minimize their chances of being eaten by smaller predators.


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


    Well preserved skull of a Parasaurolophus found. The skull is interesting because it belonged to a juvenile and shows exactly how the iconic animal's crest was formed. It also confirms the short-crested Parasaurolophus cyrtocristatus as a valid species (the long-crested Parasaurolophus walkeri is the one most often depicted in popular media).


    http://www.sci-news.com/paleontology/parasaurolophus-cyrtocristatus-09292.html

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