The Ornithopod Thread- Hadrosaurs, iguanodonts and kin

Capt'n Midnight

Fathom wrote: »

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

IIRC 2 meters is the maximum depth underwater humans can breath through a tube to the surface.

And the guy who tried it died shortly afterwards, so do not try at home.


Human lungs aren't made for that differential.

Adam Khor

:eek:



I wonder what would happen in this scenario then :B

Capt'n Midnight

Adam Khor wrote: »

:eek:

https://dino.lindahall.org/img/bur1m.jpg

I wonder what would happen in this scenario then :B

In two words I can tell you what's the matter with it: It's im-possible.
- Samuel Goldwyn

Adam Khor

But that's good news for fossil preservation:

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

Adam Khor

Or hadrosauroid. Skeleton said to be nearly complete and as well preserved as if it had died days ago, thus allowing for great, accurate reconstruction:

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0208480

Adam Khor

From the North Dakota Geological Survey's Paleontology Resource Protection Program's Twitter account, comes this very interesting picture which shows the hand of famous Edmontosaurus "mummy" Dakota, one of the best preserved dinosaurs in the world.

The picture shows that we have been reconstructing hadrosaur "hands" the wrong way; instead of three separate digits each ending in one small hoof, it appears these animals had all three main digits completely covered on a skin and flesh "mitten", and only the third digit had a big, horse-like, weight-bearing hoof. So, externally, the creature would only have one apparent hoofed toe, and a small, spike-like "pinky" that didn´t touch the ground.



Yet another example of how little we actually know about dinosaurs- even "classic" ones like Edmontosaurus-, and how different they would look with all their fleshy bits on.

Adam Khor

Big news! Cartilage cells with traces of the original proteins/DNA found in juvenile Hypacrosaurus fossils!



https://newatlas.com/science/dinosaur-dna-proteins-fossils/

These particular specimens were “nestlings”, meaning that at time of death they weren’t yet old enough to leave the nest.

Inside the skull fragments, the team spotted evidence of extremely well-preserved cartilage cells. Two of them were still linked in a way that resembles the final stages of cell division, while another contained structures that look like chromosomes.

The next step was to check whether any original molecules or proteins could still be preserved, and to do so the team conducted two detailed analyses on other skulls from the same nesting ground, and compared the results to samples from young emu skulls that are (obviously) much more recent.

The first was an immunological test, which involves applying a substance that will react if it detects antibodies from a particular cell type. In this case, the test reacted to antibodies of Collagen II, a protein commonly found in the cartilage of animals. This, the team says, suggests that remnants of the original proteins are still present.

Understandably, the reaction was far fainter for the dinosaur samples than the emus. The dinosaurs’ staining was also localized in one spot, where as in the emu it was spread across the whole sample.

In the second test, the team hunted for dinosaur DNA. They isolated individual cartilage cells from the Hypacrosaurus, and applied two different staining substances that bind to DNA fragments. And sure enough, the staining occurred in the same pattern expected for modern cells.

The implications of potentially finding DNA in these samples are huge. Current thinking says that DNA can only persist for about a million years maximum – but these fossils are 75 million years old.

"These new exciting results add to growing evidence that cells and some of their biomolecules can persist in deep-time,” says Alida Bailleul, co-lead author of the study. “They suggest DNA can preserve for tens of millions of years, and we hope that this study will encourage scientists working on ancient DNA to push current limits and to use new methodology in order to reveal all the unknown molecular secrets that ancient tissues have.”

While Jurassic Park remains firmly in the realm of fiction, the possibility that dinosaur DNA and organic molecules could persist for tens of millions of years is still fascinating, and it could teach us far more about these captivating, ancient creatures.

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.

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

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).

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.

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

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.




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.

Fathom

Adam Khor wrote: »

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.

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.

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.

Fathom

Adam Khor wrote: »

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.

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

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/

Fathom

Adam Khor wrote: »

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.

Read about various climate change models. One or more suggested that global warming would not be a simple straight line event. Rather, there may be a tipping point. Beyond which change may go up geometrically. From gradual to more sudden and consequential. Cannot remember the source. Perhaps from materials promulgated by Al Gore. Would hadrosaurs float without the aid of swimming? Then move their legs and tail to navigate?

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.

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

Fathom

Wonder why Hadrosaurs were so prolific?

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).



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.

Fathom

Thanks Adam for indepth answer. Something I could sink my teeth into.

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