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Sailbacked iguanodont found in Spain
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17-12-2015 1:30am#1
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Ouranosaurus is apparently somewhat more recent and more developed than Morelladon. The two species, superficially similar, might have had similar lifestyles; but the dorsal sail does remain a mystery. In the case of Morelladon, it was too small for fat storage or even for body insulation. Perhaps it served no other purpose than to keep small predators from leaping onto these herbivore's backs.
I don't see how it would be too small for fat storage. It looks larger than say, a camel's hump. But then a camel's hump is not supported by tall spines IIRC. The sails of Morelladon and Ouranosaurus remind me more of a Gaur's ridgeback. I am not sure of the function though. It may be as simple as making the animal look a lot larger without adding too much additional weight.
Notice how tall the Gaur's spines are.
Compare to Ouranosaurus:
They look almost the same.0 -
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But I'm still not convinced that these Iguanodontidae had dorsal sails for the purpose of fat storage.
I don´t believe it either. Modern day lizards and crocodiles store fat mostly in their tails. Seeing as dinosaurs have large tails similar to theirs, I would imagine they probably did the same.I'm still opting for my theory that these served for defense in case of attack. Raptors and similar small to medium, ferocious theropods most likely had the habit of jumping onto the back or neck of their prey
Problem is we don´t have any remains of raptors or similar creatures from the same time and region as Ouranosaurus. On the other hand, we know it coexisted with larger predators such as Eocarcharia (a carcharodontosaur) and Kryptops (a supossed abelisaur), as well as the spinosaur Suchomimus, although the later probably specialized mostly on fish and rarely attacked large dinosaurs. The remains of the former two predators are really incomplete, however, and apparently mixed with one another so we really don´t know what they looked like, let alone how they behaved.
As for Ouranosaurus itself, I think only a couple skeletons are known; I have no idea if their sails are about the same size or if one has a larger sail than the other, thus accounting for the different reconstructions., hoping to bite through the jugular veins and arteries. Larger predators would have gone straight for the neck and base of the skull, which they could have snapped with ease.
This seems to me like an assumption based on the killing methods of larger predators today. Sure, lions and tigers and weasels and what have you usually go for the neck, but that's because they are precision biters; their canines are especially designed to puncture the neck and dislocate the vertebrae, or crush the windpipe and sever the main veins and artheries, or even (if the victim is too large and the fangs can´t go in too deep), to suffocate the victim.
But most carnivorous dinosaurs had very different jaws and teeth; they didn´t have canines, and their teeth were all of similar size and shape, usually blade-like and serrated. They were not meant to puncture, but rather to slash and bite off large chunks of skin and flesh. This tells us they were most likely operating in a manner more reminiscent of sharks or Komodo dragons; they would've given a devastating bite and then wait for the victim to collapse from shock and blood loss, perhaps biting several times if necessary. Really messy compared to say, a lion kill. And if you look at shark and Komodo dragon attacks, they don´t go for the neck; they actually tend to go for the least protected parts of the body, away from horns or teeth that may in turn cause them injury.With sails to protect their vulnerable spines and neck, iguanodonts and hadrosaurs would have had more chance to survive.
Except not all iguanodonts and hadrosaurs had tall back spines. Look at Iguanodon proper; it has very modest spines.
Same goes for Mantellisaurus (formerly regarded as an Iguanodon species)
And Lurdusaurus, which coexisted with Ouranosaurus and its predators.
If the sails had been such a great protection against predators, wouldn´t you expect to have more sail-backed iguanodonts?
I think they already had great defenses in the form of their powerful arms and deadly thumb spikes. They probably faced their enemies bipedally anyway (as a last resource if fleeing wasn´t an option), and recent studies show large ornithopods could turn around quite fast, which makes me think that, if cornered, they would've tried to face their enemy at all times until it gave up, not unlike a buffalo trying to face a lion with its horns at all times and prevent it from attacking its rump. There's even a possibility (although this is wild speculation) that they would've faced their enemies as a group. You know, kind of like musk ox or bison making a circle or a wall of horns to deter wolves.
Regarding hadrosaurs, consider this; there is good evidence that Tyrannosaurus rex, the most devastating biter amongst predatory dinosaurs, often attacked the back and hip region of its prey presumably to paralyze them; if tall sails were meant to protect the spine, wouldn´t we expect Edmontosaurus, T. rex's favored prey, to have the tallest and sturdiest spines of them all? Yet its spines are really modest.
So I don´t think the tall spines were for defense, either. We do need more specimens; if it turns out males and females had different shaped/sized sails it may very well have been a sexual display thing, or perhaps designed to make them appear larger to the eyes of potential predators.0 -
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Hello Adam,
As usual, you've made some good observations; but I differ with you in certain opinions.
I wouldn´t expect less
Theropods in general were no dumb brutes; they must have observed, by experience, that a sharp bite to the jugular killed their prey quickly.
So going by that logic, sharks, Komodo dragons, wolves, hyenas, jaguars, crocodiles and the many other predators that usually dispatch prey by biting somewhere else and not necessarily the jugular are dumb brutes?What is more, T-Rex and all the treropod predators were bipedal; the largest of them stood mostly at a level with their victim's neck.
Actually if you compare T. rex with its usual prey, it would've towered over most of them. Evidence in the form of bite marks on the skeletons of herbivorous dinosaurs indicate it would usually attack the hips and tail region in order to cripple its victim by crushing the spine or destroying the caudofemoralis muscle (which dinosaurs used to power their stride). This allowed T. rex to disable its prey without having to face the beak, horns or what have you.If T-Rex and company really ambushed from behind, they might have been able to pounce on their prey and floor it with a swift stabbing bite to the base of the neck.
Not sure what you mean by stabbing bite (sounds to me like a sabertooth tiger's MO). Some dinosaurs such as Allosaurus may have operated like that (although again, Im not sure they went necessarily for the neck), but T. rex was a lot different; its jaws were not designed for a quick and precise bite to the neck but rather for crushing massive hip bones and ribcages like they were crackers. Some studies have shown T. rex could bite with a force superior to that of a hydraulic car press; imagine what this would do to another animal, no matter how big. I don´t doubt T. rex went for the neck and head of its prey at times but I doubt it would simply sever the jugular; with such powerful jaws (and the brutal head shaking it was apparently capable of) it would've easily bitten the head off most prey.
Mind you, T. rex was an exception amongst theropods rather than a rule; its teeth had a different shape than those of other giant carnivores. If you look at T. rex teeth, they are round or oval in cross section, thick like giant nails or railroad spikes, and internally designed to whitstand extreme forces; they were meant to destroy bone, rather than simply deal with soft flesh:
This along with the very massive structure of the skull suggests the T. rex was going for massive structural damage rather than precision bites.
Now compare with the tooth of a Giganotosaurus, which has a much more "traditional" tooth design:
The typical theropod tooth is laterally compressed, like a knife, and with very sharp edges; it was like I mentioned before, quite similar to the teeth of a Komodo dragon, and functionally also a lot like a shark.
The skull of these typical theropods was also a lot lighter and less reinforced than a T. rex's, meaning they were doing things very differently.
I think that the iguanodonts used their thumb spike more for the purpose of slashing at the abdomen and other tender parts of bipedal predators, than for going at the head.
The thumb spikes are conical rather than blade-like; they weren´t good for slashing. Instead, the strong arm musculature and range of motion suggests they were made for stabbing. They may have been precision weapons, designed to puncture an attacking theropod's neck, chest or ribcage if it got too close. If an iguanodont tried to go for the abdomen of a theropod it would be putting itself at risk by not minding the dangerous end of the carnivore. No, I think iguanodonts were well equipped to confront their enemies face on.Why didn't more iguanodonts develop dorsal sails? Mother Nature has her ways, and those are mysterious. The best we can do is to ask HER that question! Perhaps it was due to the fact that some iguanodont species had less predatory adversaries than others.
Or maybe the sailless species spent most of their time in lakes, rivers etc., for the scope of protection.
This actually is intriguing. If you consider Ouranosaurus and Lurdusaurus, they both lived at the same time and in the same regions, but Ouranosaurus was seemingly a land-dwelling animal whereas Lurdusaurus was semiaquatic. Ouranosaurus had a sail and Lurdusaurus did not.
Still, I don´t think this proves the defensive function of the sail. In fact I think it points to a stronger possibility; Lurdusaurus was probably spending lots of time in water, and Ouranosaurus was not. These animals lived in a very hot environment. Maybe they were simply using two different ways to regulate their temperature. Lurdusaurus would've kept cool in the water, whereas Ouranosaurus would've use its sail to radiate excess heat like an elephant's ears.
More potential evidence supporting this; Suchomimus, a spinosaur from the same time and place, had a small ridge or sail on its back too, intermediate between the normal-sized spines of say, Lurdusaurus, and the tall ones of Ouranosaurus. Which makes sense if we consider the inferred lifestyle of Suchomimus, a fish-eater that would wade and patrol shallow water for prey, but was probably not as aquatic as Lurdusaurus. It would've benefited from both kinds of thermorregulation.
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Hello Adam,
Believe me, in these discussions I'm not arguing just for argument's sake. It's not my desire to be the devil's advocate. You have much more technical knowledge than I in the field of palaeontology; you have much more material evidence to draw on, I often act upon plain gut instinct. We often see things in a different light. That does not mean that I categorically reject your points of view. To the contrary: you often point out important aspects of which I had not been aware previously.
I do have an uncanny ability to reconstruct possible scenes from prehistory in my mind. I often make clay models of dinosaurs and other extinct creatures, placing metal weights inside them to give them proportionate volume. Then I manoeuvre them in confrontation one with another, or alone, to see how swiftly they could have moved in real life. One experiment I conducted several times, with different species models, was to see if a typical large sauropod, when being attacked frontally by a huge theropod, could swerve its body fast enough in order to wallop the predator with its tail. The answer was invariably NO; the fast theropod would have been upon the sauropod before this unfortunate herbivore had time to maneuvre into position. So I came to the conclusion that the sauropods could have effectively clobbered their giant foes with their tails only in the case of a rear or side attack.
Of course, this was just an experiment with models. But one thing that enthralls me is the strangeness of life on Earth before man. It was another world altogether: different predators from those we know in our times, and different prey. Different lifestyles and methods of hunting. When I spoke of the large theropods as possibly neck-biting beasts, I was not trying to single out T-Rex as typical. Indeed, as you so very carefully demonstrated in your last post, he was an atypical species in many ways. But Allosaurus, Albertosaurus, Gorgosaurus and the rest MAY have used hunting tactics designed for a quick kill, aimed at their prey's neck and spine.
By the way, I never meant to deride sharks, Komodo dragons or any other modern species. They have their own ways and their own logic. My point was just that prehistoric creatures, living in an environment considerably more perilous than our own, had to be pretty sharp and use all their wits in order to survive, to have advantages over their contemporaries. Amazing chaps, those dinos. They combined instinct and reason in ways which we will probably never comprehend. And everything they did was done "their way", as Frank Sinatra would say.
One of my dearest goals...and surely the most difficult!...is to endeavour to penetrate into those ancient dinosaurian minds.
But aren't all of us palaeontologists, amateur and professional, essentially trying to do the same?
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Believe me, in these discussions I'm not arguing just for argument's sake.
Oh, I know.One experiment I conducted several times, with different species models, was to see if a typical large sauropod, when being attacked frontally by a huge theropod, could swerve its body fast enough in order to wallop the predator with its tail. The answer was invariably NO; the fast theropod would have been upon the sauropod before this unfortunate herbivore had time to maneuvre into position. So I came to the conclusion that the sauropods could have effectively clobbered their giant foes with their tails only in the case of a rear or side attack.
I actually think this makes perfect sense. While sauropods are often misportrayed as being walking meatbags just waiting for something to come and bite it to death, they look like they were actually really dangerous animals if one looks closely enough to their anatomy. Their size alone would've been a defense already but, as if that wasn´t enough, many of them had claws on their forefeet (look at the large thumb claw on this Apatosaurus for example)
The claw was particularly large in diplodocoids, which had very large and muscular hind legs compared to the forelegs, so there's a good chance they could rear up to face an attacking theropod and use their claws for defense. A lot like the famous Barosaurus vs Allosaurus skeleton mount at the American Museum of Natural History:
So really, the sauropod would've been dangerous on both ends; if the predator attacked from the front, it risked being crushed or seriously injuredby that claw. If it attacked from the sides it would risk being hit by that supersonic whip-like tail. Attacking from behind directly would be suicide.
Brachiosaurs apparently lost the claw eventually, but this also makes sense because their forelegs became longer than their hindlegs and they probably didn´t rear up so much. Titanosaurs apparently lacked the foreclaws altogether but then again they lacked the whip-like end to the tail too, so they must have used some other defensive technique (we know many of them had armor, so there's that).One of my dearest goals...and surely the most difficult!...is to endeavour to penetrate into those ancient dinosaurian minds.
As minds do not fossilize, it is indeed a difficult goal
But aren't all of us palaeontologists, amateur and professional, essentially trying to do the same?
I've always considered myself more of an artist than a scientist really. But I am indeed fascinated by all living and extinct creatures and I do love learning and pondering. I do enjoy our discussions because even though we don´t have the fossils themselves to study (and honestly, I doubt I'd know how to go about it if I did!), I think sometimes we do reach reasonable conclusions based on what little info we get from the professionals out there. At the very least it's a lot of fun. 0 -
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