Iguanodon: Your Dinosaurs Are Wrong

[Music] uh it has intrigued paleontologists and audiences alike for nearly two centuries now since its fossilized remains were first exhumed from the earth our imaginations have run wild trying to recreate what this magnificent beast looked like with the passage of time and recovery of more specimens science's persistent march has revealed much of their true nature from hulking monstrous reptile to versatile muscular dinosaur new interpretations of its remains have vastly changed our hypotheses about their appearance and behavior it was among the first known to science and to capture the imagination of the public the more we've learned about iguanodon the more we've learned about our relationship with and approach to paleontology [Music] so it would appear that people want us to do a guanodon at least based on the number of iguanodon toys that they have sent in for us iguanodon was a large ornithopod from the early cretaceous of europe which by a quark of fate might be the most important dinosaur we've found iguanodon defined what a dinosaur is to both the public and the scientific community in the 19th century and as paleontology grew up our understanding of iguanodon grew up with it which does mean that our picture of this animal has often reflected our human notions about the past as a whole more so than the actual biology of the animal but we have gotten better iguanodon is from a group of strata in europe called the wieldon there are some animals that have been referred to iguanodon from elsewhere in the world but it's not clear that they actually are iguanodon workers have referred a lot of remains to iguanodon over the years in this diagram the thickness of the central bar reflects how species-rich the genus was at a particular time by the end of the 20th century we had at least a dozen species but recent work has clarified that no many of these animals should be considered separate genera the first wielding remains that are attributable to iguanodon were actually found in 1809 but it wasn't until the 1970s that anybody noticed that oh hey these are probably iguanodon so our story actually begins in 1822 which for reference as to how young the field was that's the same year that the term paleontology was coined the story goes that dr gideon mantel was on a house call and his wife marianne woodhouse was taking a walk and just happened to see some unusual looking rocks in a pile of road metal that is a gravel for paving and once she alerted gideon to these rocks he noticed that they were these unusual looking teeth not everyone believes this story mantel himself later said that he was the one who found the teeth though this was after he and his wife had split up so maybe ulterior motives most material in this period arguably in any period was actually found by people who dig for a living you know miners and quarry men and the mantle specifically bought a lot of their fossil collection from quarry men who were working in sussex the names of those people have not come down to us and i'm not just quibbling here i i want to emphasize we often say you know gideon man tell this and richard owen that but the process of piecing together a guanodon was collaborative from the very beginning mantel got william buckland's opinion on the teeth buckland is most famous for describing megalosaurus mantel sent the teeth to charles lyle the geologist who then showed them to baron coughier in paris this the story is that he was at a party and showed these strange teeth to cuvier because fossil nerds have not changed in 200 years and cuvier initially said that they were clearly rhinoceros teeth but a day or so later he changed his tune and realized that these were some kind of herbivorous reptile which at that scale was very strange at the time it was a mr clift who realized that a living herbivorous reptile is the iguana and it was a mr strathberry who had recently prepared a specimen of iguana which i assumed to be a skeleton for the museum which mantel and mr cliff were able to analyze all of this process took three years so it wasn't until 1825 that the description of the iguanodon teeth was actually published i didn't know this but the plates in that were actually engraved by mrs mantel marion woodhouse iguanodon is sometimes underwhelmingly described as the first herbivorous dinosaur that kind of sells it short like megalosaurus had been described at this point by william buckland but we had big lizards we had big crocodiles these are within human experience and we didn't know what theropods looked like yet so it was thought that megalosaurus was just you know a big lizard whereas a giant terrestrial herbivorous reptile was very strange that was the first indication that this group of animals that we didn't even have a name for yet the dinosaurs were something special these original teeth have a complicated status mantel didn't actually specify a species if you excuse the redundancy he either didn't think he could or was just inexperienced and didn't realize that he needed to so traditionally they've been referred to as iguanadon mantalai but i think that makes them iguanadon anglicum now did you know that mantel actually didn't come up with the name iguanodon he wanted to go with iguanosaurus but it was uh the geologist coney bear who suggested that it should be iguana tooth but anyway david norman this century the 21st century noted that the teeth of a related but younger animal barolium which is not a great name for a genus because if you try to google it it's like the element beryllium but it's not spelled that way anyway the teeth of that animal are remarkably similar to the lectotype of iguanodon anglicum so it's possible that the teeth that started off a guanodon are actually from barolian not that it exactly matters because those original teeth are non-diagnostic by modern standards as i just implied there there are a lot of animals with very similar teeth to this so just comparing an animal you've found to these teeth isn't generally enough to say oh this is clearly this genus and species cherig and chapman pointed this out in the 90s and suggested that instead we should use one of the extremely complete very well preserved uh specimens of iguanodon from burnosart iberno sartensis as the type and in 2000 the iccn adopted this proposal so if you're the kind of person who cares iguanodon is belgian now not english not that having only teeth to go on was any impediment to early workers there was a school of thought at this time that is called anatomical correlation it is this idea that given just the smallest scrap of information like the tip of a feather or you know a few isolated teeth you can extrapolate using your human reason and your study of comparative anatomy the entire animal so initially as you might expect workers reconstructed it essentially as a giant iguana early artwork is a bit inconsistent sometimes they're portrayed as essentially an iguana but just big sometimes they're portrayed more like a moses are with legs like like a whale on land but always enormous mantel in 1825 estimated its total length as 21 meters he would have used feet but i'm converting it for ease of comparison but by the time of the 1840s this had ballooned out to 40 meters or more by owen's reckoning and as heavy as six elephants for reference this would be longer and heavier than the biggest known sauropods today now that we have complete remains we know that they were around 10 meters in length and something like three tons now it's easy to laugh at the overconfidence some would say arrogance of the victorians but it's not like we would do that much better using modern tools if all we had were these teeth and we didn't know you know what an ornithopod is if we didn't know what an ornithischian is and all we had to compare it to was an iguana and a crocodile like we would recover that it's an animal that chews and has socketed teeth so it's a big herbivorous crock like i'm afraid i come across as dismissive on this show i don't think early workers were stupid i think they were brilliant they just didn't have the generations of information and tools that we have now they didn't even have evolution by natural selection you know the foundation of modern paleontology so while the artists were drawing whale lizards the paleontologists were adjusting their hypothesis as they got new information in fact what mantel wrote was a bit more nuanced than just giant iguana he and a worker named melville looked at the way that the teeth were ground down and were able to extrapolate some things they figured out that each lower tooth was contacting two upper teeth and the way that they contacted was in a sliding motion at their tips they had the enamel of the upper teeth grinding against the denting of the lower and vice versa so as the teeth wore down they maintained a hard grinding edge melville compared this to a pair of chisels which is not a great analogy but i want to compare it to the action of a paper shredder which isn't much better nowadays thanks to the work of godafrat and especially naba vizada we know that the actual motion of the mandible of the jaw bones was more sophisticated than that the denturies could actually rotate during the feeding stroke they would rotate inwards while moving backwards they would pivot against the predental bone this meant that one they could chew on both sides of the mouth at the same time and two chewing pushed food down the throat it's a very efficient system it's not as sophisticated as what we see in their relatives the hadrosaurids but then what is but at the time workers were quick to infer that an animal is going to have this chewing apparatus for a reason even though they didn't know the full extent of it they knew that it would be processing woody brows and indeed they found teeth associated with remains of conifers cycads and tree ferns so they figured that these hard plants would be its preferred food we can't 100 say that that's the case because there's preservation bias hard plants are going to have an easier time fossilizing than soft plants and just because an animal can chew hard stuff doesn't mean it's always going to eat that as early as 1827 mantel thought that unlike modern lizards who don't chew a guanodon was going to need extra oral tissues for taking food into its mouth and for holding it there once it's in there he thought that they would have mammal-like cheeks lips and a prehensile tongue cheeks on ornithischians are more or less still with us although iguanodon specifically went without them until about the 1980s i think this is due to owen's influence but some of these toys portray sort of mammal-like muscular cheeks which is not reasonable for a saurian the only reason we have these is because we need to be able to suckle if you don't have that selection pressure there's no reason to move the muscles of your face that far forward what is less clear is whether they could have had some kind of membrane on the sides of their face or whether there was a horny bill or whether they just had lizard-like lips the main objection to putting membranes back there to hold food in is that the living relatives of dinosaurs crocodiles and birds don't have any structure like that the california condor i believe does have sort of a pouch in the back of its face but it's not for holding food it's an inflatable display structure which would look neat on a guanoton but not what we're talking about so if we wanted to bracket cheeks as a trait it would be a level three inference because we need osteological correlates to say that they're there we do have osteological correlates but it's not super clear whether they actually indicate cheeks most derived ornithischians iguanodon specifically does have this have a shelf above and below their teeth they have their their tooth throw is insect from the sides of the skull so if you look at it it's easy to imagine a membrane stretched across that valley there's also rows of little holes along the ridge on the dentury as well as along the back edge of the pre-dentary but it's not clear that those foramina correlate to cheeks because those four amina at the front are clearly supplying nutrients and blood to the keratin beak not to any kind of fleshy structure so what are the foramina further back doing it could be that they're supplying lizard-like lips it could be that they're supplying a sort of softer marginal beak sort of like what you see in birds where the front portion of the beak is mineralized and hard and the back portion of the beak is a little more flexible i won't say don't put cheeks on iguanodon but you should know what you're doing and only put them as sort of a hyper-trophied richtus back where the molars are don't do what for example this toy does and have them all the way at the front of the mouth and sort of chubby okay enough about teeth moving into the 1830s we started to find more bones from iguanodon a lot of these were isolated but notably we found the saul specimen from the isle of wight which is a sacrum of an iguanodon which owen used when defining dinosauria he only included three genera in his original definition which were iguanodon hileosaurus and megalosaurus but he wrote that the characters that he was able to identify in that iguanodon sacrum were the basis of his definition as a side note owen was not the only worker in the world to recognize that these animals formed some kind of group but he was the first one to get a name across the finish line which is probably for the best because your pachypods are wrong doesn't sound quite as good that's a von meyer deep cut another notable specimen was the mainstone specimen this was found in a quarry owned by a william benstead and it's not clear to me the sequence of events here but somehow they wound up driving a blasting charge right through the middle of the specimen and blowing it up and they had to gather up all the pieces off of the quarry floor and benstad had to painstakingly reassemble it and sort of half prepare it and then they presented it to gideon mantel and it's been affectionately known as the mantel piece this is the origin of that famous sketch you've probably seen where it's a dashed line that looks vaguely like an iguana and it's walking on some kind of tree i suppose that's supposed to be even though it looks like a backbone but we still didn't have a head or neck and this is as far as i could tell the origin of placing the thumb spike on the nose as a consequence of the fact that it was blown out of the side of a quarry we don't exactly know this specimen's age anatomically it appears to be what was later named iguanodon atherfieldensis which today is known as mantalosaurus so this specimen isn't actually even a guanodon anymore so if you see an iguanodon with skinny little forearms like this toy or possibly this toy arguably that's probably actually mantellosaurus another side note maidstone is quite proud of this specimen they put iguanodon as a supporter on their coat of arms which i think might be the only non-avian dinosaur used in that capacity in the 1840s a more complete dentary and a partially complete maxilla gave mantel some ideas he noticed that if he mirrored that dentury and and put them together they superficially resembled a myelodon a giant ground sloth mandible he thought that the toothless tip of the snout was supporting prehensile lips and that these deep pits on the inside of the jawbone were anchoring a long prehensile tongue or the muscles to move it so instead of a whale iguana he started imagining a much smaller animal maybe five meters long excluding the tail ecologically similar to a mastodon or the modern elephant the idea of a guanodon with a long prancel tongue sticking out of its mouth stuck around for a really long time i saw artwork of this all the way into the 80s this toy from 1970s vintage still has the tongue sticking out of its mouth dolo often gets blamed for this and he did not refute it even though he knew that the animal had a beak but it seems to have originated with mantel as far as i could tell some have taken mantel's comment about how the front limbs were more gracile to mean that he was thinking of iguanodon as a biped as an animal that walked only on its hind limbs i think they're probably reading too much into it remember he was conceiving of this animal as a semi-aquatic ground sloth so ground sloths would walk on their hands and use their hands to manipulate foliage that's all he's arguing the case for a bipedal iguanodon had not been made is how whitten chose to phrase this but why was he concluding that it was semi-aquatic well there were some caudal vertebrae tail vertebrae known at the time and they had very long spines on the tops of them these were interpreted as a paddle we now know that having long neural spines at the base of your tail is not actually useful as a paddle which if you think about it you don't paddle with the base of your tail it just it doesn't move that much what you would expect to see in an animal that's paddling with its tail is long transverse processes to anchor the muscles it wasn't until the dinosaur renaissance that ulstrum actually pointed out that the baskets the the interwoven tendons ossified tendons along the spine of guanodon and other related animals was a stiffening device they they had these high stiff rigid backs and tails that were held horizontally straight out they weren't using them as a paddle around this time richard owen started arguing that the horn that mantel had put on the animal's nose was actually an angul a fingertip bone he didn't put it confidently on the thumb he concluded that it was probably an outer digit so either a thumb or a pinky in our terms owen's argument was that the base of the spike had an articular surface which you wouldn't expect to find on something that was attached to the nose of the animal whereas a thumb has to be able to rotate even though a guanodon specifically couldn't move very far it seems to have moved as a unit with the first knuckle of the thumb as well and in related animals it's actually all fused together the the wrist is one big block with the thumb now mantel argued that it couldn't be an angul he thought that it was either a nose horn or one of a series of dorsal spines down the animal's back sort of like what we're envisioning for hileosaurus at the time and funnily enough his argument in favor of that is because the thumb spike that he had was not like this one his didn't have these furrows down either side which is where the quick i don't know the technical term for it the the part of the claw where it grows in that's where the nutrients for that are we now know as of uh verdu at all in 2017 that individual iguanodon might lack those furrows for whatever reason it's really inconsistent sometimes they'll have a furrow on one side and not on the other sometimes they'll have furrows on their left thumb and not on their right thumb it's extremely variable so it's just bad luck on mantel's part that he got one that didn't look like an uncle but what was the thumb spike for almost everyone has agreed that it is some kind of weapon that it might be potentially used for breaking into hard plant materials but really it's a big spike on the animal's hand it feels like something it would be using either for defensive against predators or for intra-specific competition or both cool did a finite element analysis of the wrist bones and found that the way that the wrist bones are fused is really good for bearing stabby stresses it's it's good for driving the thumb spike into things her analysis didn't include things like is it good at bearing stresses this way so further research required on that one but that same individual variation paper verdu at all found that there are two distinct morphs of thumb spike some relative to the size of the base of the spike have a very short spike and some have a very long spike and whenever you have two morphs of an animal workers kind of want that to be sexual dimorphism but in this case it kind of makes sense because maybe the males were competing for mates and they had their thumb spikes either as deterrent you know as just a display or like how roosters will have spurs and they fought each other it's not an unreasonable conclusion talk dumb get the thumb we don't have to leave that one in but that's all in the future because the spike knows iguanodon is about to become famous the crystal palace company hired benjamin waterhouse hawkins and his team to sculpt life-sized replicas of a bunch of fossil organisms uh the star attraction of which was a pair of iguanodon we have records of the production process and it's pretty similar to how you would go about it today uh hawkins started with a rigorous skeletal reconstruction along with an outline of the body of the animal guessing as best they could based on living animals where the muscles in the skin would go then built that outwards into a 3d model once they were happy with the miniature they scaled it up to the life-sized version now life-sized in this case was based on the great horsham iguanodon which it turns out is probably bar liam but it turns out borolium is about the same size as a guanodon so they scaled it to 10 and a half meters which is pretty close even though the actual animal is quite a bit different from iguanodon as we know it today waterhouse hawkins was using material from a number of specimens and mark whitten makes the point that it's possible that none of the bones he was using were actually iguanodon some of them were barillium some were what we now call mantolosaurus and some might have been uh hippolyspinous i do recommend checking out mark whitten's series of blog posts about the crystal palace sculptures not just iguanodon he talks about all of them as well as the friends of the crystal palace sites if you're interested in this at all there's a lot of information about this but we're going to focus on the anatomical details now that life-sized sculpture is the model that they held a famous dinner party in on new year's eve of that year but they then took casts of the surface of it which they would use to pour the concrete on the real version but the reason they could have a bunch of people inside the body cavity of the iguanodon is because they were restoring it as this heavy broad-bodied broad-shouldered pachyderm-like animal whereas we now know that it's deep-chested but fairly narrow-chested too it's you know a pretty bird-like ornithopod but hawkins figured that being an herbivore it would need a lot of guts to digest all of that food and everything kind of followed off of that if it has this gigantic gut well then its legs must be heavy and stout to support it he restored the head basically in line with an iguana's head though there's some differences it is wider than mantel's idea of how wide the head was supposed to be which is interesting but the neck is also extremely thick and robust which is an interesting contrast to what's coming it's hard to tell on this particular model but if you look at photos of the statue as it exists today you can see that at the front of the mouth the upper lip if indeed it is a lip slopes down to sort of interlock with the edentulous portion of the front of the lower jaw you see we still didn't know about the pedentry i don't think we knew about the burdenery in any dinosaur but they restored these iguanodons with this sort of beak-like scale on the front and i don't know if that's actually supposed to be a beak if you look at a rhinoceros iguana some of them will have these big scales at the front of their mouths others don't but i do wonder if that's what hawkins was basing it on and not giving it like a turtle like or bird-like beak though if they did give it a beak i mean that's not unreasonable they did have a beak uh i feel like if it were though owen would have mentioned it and i couldn't find anywhere that owen mentioned the possibility even of them having a beak and subsequent paintings by waterhouse hawkins seemed to lack it as well on the subject of the integument of the animal the skin and horn and scales we basically had nothing at this point we had a little scrap of fibrous tissue that is probably dermis but we didn't have the surface texture we didn't know about the turbo girl pavement so hawkins restored them with iguana like scales this is most obvious in the head where they have very iguana-like sides of the head with that big tympanum we would get a glimpse of the skin of a guanodon from the find in burnasart but really ornithopod integuments specifically and dinosaur skin in general would come into focus in 1912 when we found this exquisitely preserved edmontosaurus mummy in america the skin of these animals was broken up into polygonal tubercles it's the pavement that you see kind of by default on most dinosaurs this would be confirmed by the holotype of what is now mental asaurus from the isle of wights in the 1920s it preserves a little patch of tubercle pavement now the final iteration of a guanodon that i used in our end credits animation has these sort of quills going down its back i included those as an indication that we don't know whether it might have had some kind of keratinous or even proto-feather integument we know that ornithischians could have some structures like that you know calinda dromaeus exists tanyalong exists we know that stuccosaurus had this row of quills we don't know of anything like that on a close relative of a guanodon but we also don't have a guanodon integument from an environment that would have preserved any kind of filaments or keratinous structures as far as i could tell so it's not unreasonable to put that kind of thing on there in my opinion not that any of these toys do anyway in any case the crystal palace models were an incredibly popular depiction they kicked off the first major spell of dynomania among the public so this depiction of iguanodon had pretty wide pop cultural purchase even though it was not state of the art scientifically for more than a couple of years because there was new material coming out of america and waterhouse hawkins was involved in that too joseph leedy got him in to mount and sort of finish his hadrosaurus skeleton that he had found hawkins had to reconstruct most of the front half of the animal he still gave it a pretty lizard-like head and a short neck but he restored it as a biped he looked at rat type skeletons and kangaroo skeletons the kangaroo part is pretty evident in the way that the shoulder looks and restored it in this tripod very upright stance much like these toys i've often called toys that are posed like this with them standing on their tails scaly kangaroos this is the origin of that it was kind of codified by louis dolo whose skeletal mount was in this same pose and those skeletons got sent while replicas of those skeletons got sent all over the world but that trope seems to have originated with waterhouse hawkins and his heterosaurus mount i mentioned this because hawkins applied much of what he learned from hadrosaurus to iguanodon in 1877 he painted some iguanodon and they are very similar to his hydrosaurus except that they seem to be quadrupedal they're sort of weird frog birds they don't appear to have a like pseudo-beak like his crystal palace version did though their upper lip does still curve down into the gap on the lower jaw they appear to have their spike on the pinky or possibly on the sixth digit it's kind of hard to tell but they do have bird-like hind limbs the the huxley and ornithoscolidine bird legs the actual legs of a guanodon are indeed quite bird-like and most of these toys do a pretty good job actually there's it's it's a it's a chicken leg with a very short foot on it they had stout little foot bones more derived hadrosaurids were subangular grade they would stand on their toenails and their foot pad whereas a guanodon was standing on their toes but those toes were still quite hoof-like i emphasized that because their feet were adapted for walking on land but in the 19th century they were attached to this idea of iguanodon being semi-aquatic this even extended to i cannot find an image of these footprints but apparently there are some footprints that workers interpreted as showing webbing between the toes of a guanodon and if you look at the feet of a guanodon it's difficult to see where webbing would even go because they're very stubby feet this period saw a number of publications on iguanodon um owen did a series of illustrated monographs on the subject and once he was done with it suddenly a bunch of workers came out of the woodwork to name new species i do not know if this was like hey owen stopped publishing about dinosaurs coast is clear or if it was maybe more charitably that owen had laid a bunch of groundwork and people could look at what he had written and say oh these bones i have they must be iguanodon in any case as the nomenclature of a guandon was getting muddied by all these new species being named the morphology the anatomy of the animal was about to become crystallized for something like 80 years because some miners in burnosart in the mons basin in belgium were digging laterally in a coal mine about 322 meters below the surface of the earth and they hit a sinkhole of clay and in that clay they found a bunch of bones so they sent a telegraph and got what we would call a preparator i don't know exactly what his title was de paw his worker from the royal museum of belgium to go down into the hole with them and the the walls of this gallery they had opened up were just covered in bones they managed to extract some of them and were carrying them out on a plank and they started to crumble because it turns out that all of the material from the burnosart site is heavily pyritized it's been infiltrated by iron sulfide so when it's exposed to open air they hadn't even gotten it out of the mine they were still they were just in the the gallery it starts to crumble and break apart uh there's a story that depauw took his clothes and tried to like cover one chunk of bone to try and keep it from disintegrating but extracting the bones from burnishart was a process they fortunately had advanced to the point where we were able to jacket bones where you coat them in layers of plaster and extract them in a block along with the rock that surrounds them and get them out of the ground that way but preventing these bones from breaking down is a job that we are still doing like they are to this day in a glass case the climate and atmosphere of which is controlled to tr just try and keep the bones to hold together but all this effort is totally worth it because these are exquisitely preserved animals there are something like 40 individuals represented 23 of which are nearly complete and they're very well preserved there's even some traces of skin as i mentioned earlier in 2012 the duke was looking at the diagenesis of the bones the process by which they turned into rock and noted the paradox that the environment that so exquisitely preserved them that that kept them in really good condition for us to see them is the same environment that's responsible for them now breaking apart and suddenly there might be more down there it's difficult to estimate because they're not evenly distributed so we don't really know like the extent of where the bone beds might or might not be but it's possible that we've extracted as few as a third of the iguanodon that are down there but getting the rest is prohibitively expensive because there's a lot of pumping of water involved in keeping those mines accessible but in short order an author named boolenger published a description of a new species of aguanodon iguanodon bernasartensis which if you'll recall is now the type all but two of those 23 very complete individuals are iguanadon burna sartensas two of them seem to be mantallosaurus and having such complete specimens means that if you just look at how the bones are lying in the earth you're going to get a pretty accurate picture of what the animal looked like in life which means that this same year 1878 dupont publishes a picture of a guanodon very similar to these middle group of toys it's the bipedal semi-aquatic thumbs up in the air hands together scaly kangaroo with a swan neck that would endure for about a century it wasn't until the 1960s that this particular depiction would get overturned now the swan neck part of that would vary this is the earliest example i could find of that particular trope but it got the most prevalent actually after the dinosaur renaissance the most extreme example i found was of gs paul's work because of course it was but sort of in opposition to people like benjamin waterhouse hawkins or zdenek dorian those artists portrayed them with a lot of meat in their neck and it seems that that was pretty accurate there was recent work on the neck of parasaurolophus where they concluded that the long neural spines on the vertebrae at the base of the neck and at the front of the thoracic part of the animal we're anchoring a large nuchal ligament going to either the base of the head or the actual back of the head and the purpose of that ligament would be to anchor a bunch of big beefy neck muscles now the neural spines in iguanodon are not as long as in parasaurolophus also those two animals aren't that closely related but it seems likely that an animal with this long of a neck and this big of a head would need neck muscles to move it around so i'm inclined towards the beefy necked version more so than the skinny little dupont and or greg paul version i've mentioned louis dolo already a couple of times he was responsible for much of the mounting process for the bones that came out of bonus art and he spent geez something like 40 almost 50 years painstakingly describing them and his reconstruction is the one that got replicated and sent all over the world so that probably accounts for a lot of the longevity of this particular restoration anatomically the animal is mostly there the the problems with it are largely postural they were still imagining these animals as spending a lot of time in the water and they were still imagining them as dragging their tails but they were restored as somewhat active bipeds not everyone even drew them like this toy is technically not dragging its tail and there's some artwork that follows that particular trope but it's from dolo that we know that they had this deep narrow body he restored them with the forearms articulated properly with the hands facing each other he knew that the spike was on the thumb because he found articulated specimens where it was on the thumb and at last we knew that they had a beak even though looking at them it seems that none of these bipedal toys actually portray the beak they all have a very iguana-like lip on the front of them i guess yeah we'll have to go to the more modern restorations to get a look at the beak i didn't even notice that at first but yeah because it was from burnashart that we first found the predentary bone and i saw a report that somebody suggested that the prudentory was actually attached to the premaxilla so it was kind of like a um like the rostral bone in ceratopsids but that idea dolo knew better and he attached it to the front of the denturies which showed that they had this beak at the front of their mouth for cropping plants i mentioned that dolo still considered iguanadon to be semi-aquatic he saw that they had what we call the fourth trochanter i think he was the first person to call it the fourth trough hander before him it was the third anyway the muscle attachment on the back of the femur for pulling the leg back he recognized that this was an anchor point for muscles running to the underside of the tail but he thought that it was for pulling the tail from side to side for swimming so again they just really wanted to believe that these were swimmers i think based on drawings of how the bones looked while they were still in the ground the orientation of the scapula the shoulder blade that dolo used was much more vertical than we restore it nowadays it's very wallaby-like actually we know that he used a wallaby in a cassowary when building his mounts uh and even in the artwork you can see the wallaby-like forward-jutting shoulders all the way up to the 1950s in 2015 center and robbins examined the orientation of scapula in a broad swath of animals if iguanodon is similar to other basal ornithopods and somewhat unlike more derived hadrosaurids its scapula would be oriented so that its glenoid the the shoulder joint is facing backwards artists seem to have had trouble putting flesh on this frame at first you see a lot of paintings that have them looking pretty lumpy like a cat standing up as i mentioned in the middle of the 21st century zdenek buryan painted an iguanodon a few iguanodons actually with this distinctive scalene triangle sort of stance and it seems like everybody else looked at what he had done and said oh yeah that's what iguanodon looks like let's just do that meanwhile dolo continued diligently working on all of these bones he had and published a synthesis in 1923 which was the anniversary of mantle and coney beer coming up with the name iguanodon he considered iguanodon to be the ecological equivalent of a giraffe where it would be using a prehensile tongue to pulling foliage and then using its beak and chewing apparatus to process it while he was doing that workers continued to name new species we wound up with a large number of iguanodon and it might seem weird looking at it now to see one genus spread out across so many millions of years we have to remember we didn't know how long the early credaceous was back then we didn't have radiometric dating for rocks we could only sort of estimate based on well this is about how long it takes sediment to turn into rock so maybe the early cretaceous is a million years like a million years is a reasonable amount of time for a genus to endure but it turns out that the wheeled in which you know is 850 meters so half a mile thick in places actually represents something like 20 million years so we have subsequently been splitting up iguanodon into separate genre one interesting tidbit is that it seems like we have in the valenginion a pair of iguanodons we have barolium and hypsospinus so we have a big one and a little one and then in the baremian we have a big one a guanodon and a little one mantillosaurus so they're like coming in pairs as i mentioned earlier it was in the 1960s with the dinosaur renaissance that we started to conceive of these animals not as semi-aquatic swimmers eaters of soft water plants but as well-adapted terrestrial animals and this culminated in david norman's 1980 redescription of iguanodon we've already mentioned the high narrow stiff back stiffened by a basket of bony rods ossified tendons but it was with norman that we really got the modern posture the facultative biped but primarily quadrupedal horizontally backed tail straight out aguanodon now norman thought that because the sub-adult specimens we had had slightly shorter arms relative to their legs that as iguanodon aged it became less bipedal the adults would have been almost obligate quadrupeds whereas when they were younger they were more spry and they could walk just on their hind legs and their arms were shorter to reflect that as of 2017 with the verdu at all paper it's a little muddier the individual variation of the length of the arms relative to the legs kind of obscures any trend that may or may not exist between young and old animals really we need a better sample which is weird to say when we have 23 complete specimens but we need uh more young animals to really tell whether there's a trend here the modern reconstruction of the forelimbs of iguanodon is conceptually pretty close to where it was in the 1840s where it's hands that are primarily for walking on but also capable of grasping though mantel probably never imagined that their hands looked like this this toy basically gets it right the four limbs are a little gracile and the hands are pronated probably more than they should be but you can see that the middle three digits are all joined together in this sort of mit that the middle three fingers would be joined together as a mitt has been known since the early 20th century with that of montesaurus mummy oddly enough those animals were restored with like a flipper or at the very least with webbed fingers because they didn't recognize that oh no this is basically a big hoof made out of three fingers joined together iguanodon is not as derived as admontosaurus it doesn't have one big hoof the way that it seems they did but they do have very hoof-like fingernails on their second and third fingers the fourth finger you sometimes see in museum mounts and even an artwork restored with a fingernail very similar to the third finger but in arcasaurus the fourth finger doesn't get a nail and in the description of the type that finger doesn't have a big angle on it it has just a little nub there so on the whole restorations like this guy or like this toy where they have these separated kind of dainty looking middle fingers need to go away these were more like stretched out rhinoceros hands until you get to the fifth finger which was weird fingers two three and four barely clothes it probably couldn't use them for grasping it maybe could use them to you know paw at the ground but five was prehensile imagine that your thumb had like four knuckles and was also where your pinky is and you've got some idea of how iguanodon's hand worked when portrayed in quadrupedal pose it's actually kind of rare to see iguanodon shown like this with its palms facing each other it's much more common to see them with their hands pronated down and in barillium at least there seems to have been a little bit of pronation possible there there was a joint between their radius and ulna where it connects to the elbow so they could probably rotate a bit but from trackways that could be iguanodon but at the very least they are an iguanodon-like animal that's about the same size as a guanodon we know that their hands were rotated at about 45 degrees while they were walking on them on the subject of trackways at least one preserves these rough clover leaf patterns where the hind feet especially have three toe pads and then a foot pad in a clear clover leaf that's because the back of the foot had a pad on it it is not what this toy did which is have one of the toes well first off it gave it four toes for walking on which they didn't have but it puts one toe all the way backwards and it's very strange so on the whole we're closing in on 200 years of aguanodon research and there's still a number of unknowns uh one of which is just what in the world happened at burnashart to produce between 23 and 40 iguanodon all preserved in a big old bone bed workers have generally agreed that this is not a single mass death event so the entire bone bed is not one event where all 40 or so iguanodon all died the carcasses are piled on top of each other in such a way that it's clear that some died and sank down in before the next group this is referred to as attritional deposition it's the animals sink down into the sinkhole it acts like a giant funnel and once they're down in there they're protected from the subsequent erosion that took away all of the rock from the same age in that area but was the sinkhole collecting iguanodon that had died for some other reason or was it itself the cause of death if the first one then why are there no young animals in the bonus art sample all of the skeletons that we've recovered have their bones sutured and fused together the way that old animals would there's a couple that might be young adults or even sub-adults but there are no juveniles represented in this sample dolo thought that maybe there had been a flash flood and the younger spryer animals managed to escape but the old clunky animals all drowned which doesn't seem to have been what happened bernasart did have seasonal flooding but doesn't seem to have had the sort of rapid flash floods that would produce that kind of event in fact we know quite a bit about this paleo environment i've never seen a map of a paleo environment before but they constructed one it's a it's a valley with oxbow lakes and rivers running through it and the burnis art site specifically was a sinkhole in sort of a swampy lake aha a swamp so the animals might have gotten stuck in the mud it's called mired and the younger animals managed to get away but the older animals were too heavy and quadrupedal to get away well the remains are not consistent with animals that died by miring it actually takes a long time for an animal to sink in mud they don't drown they usually die of exhaustion or even starvation and they would be preserved at least some of them with their feet pointed down whereas these animals are preserved in the common death pose where their heads are rolled back over their backs also if they had been slowly sinking in mud they would have been picked at the animals would have scavenged them and at the very least their bones would have weathered and cracked before they finally submerged whereas these animals were buried swiftly and preserved exquisitely which means that they were not exposed to the elements before being washed down into this sinkhole now in 2012 bale and co-authors looked at the way that the carcasses were originally distributed in the sinkhole and figured out that it's not one bone bed it's several distinct bone beds where the animals are all oriented the same way which means that at the very least they all sank into the ground at around the same time but it's possible that they all died at the same time as well these authors think that we should revisit the idea of a cyclic mass death scenario though that does present a new problem of what could be causing such a thing um no theory that i was able to find accounts for the weirdest thing about the site which is that all of the specimens are a guanoton we have a theropod finger bone and a shin bone from a sauropod but other than that the only dinosaurs we have are iguanodon there are 117 similar sinkholes in the mom's basin and only this one has dinosaurs in it and they're all iguanodon it's weird we do have other animals there's um some crocodiles some turtles and there's a bunch of species of mud fish actually and those mud fish are a clue mudfish are unique in that they're able to gulp air if they're living in a poorly oxygenated swampy water which is what we think that this lake was and the prevalence of those mudfish suggests that fresh water wasn't flowing into this lake it suggests that it was perhaps due to a seasonal drought shrunken we don't have anything like mud cracks that you would see from a really extreme drought but seasonal shrinkage of lake is not an unreasonable thing to suggest now remember how the bones in burnosart are somewhat tragically piratized pyrite is an iron sulfide so as geothermal brines rose up they could have fed uh cyanobacterial mats forming in these waters which in turn could have produced gas clouds of hydrogen sulfide so either by drinking the water or just by breathing near the water a guanodon whole herds of iguanodon could have become intoxicated and subsequently drowned which would be pretty ironic because it would mean that the same sulfides that originally killed these animals are like back to finish the job and degrade their bones into dust to this day but as we continue to figure out just what iguanodon was be that the finer points of its anatomy how it lived and died what exactly guanodon was phylogenetically and what animals were and were not iguanodon i am excited to get to see the next part of this extremely long and convoluted story play out in my lifetime and i hope to share it with all of you thank you for watching your dinosaurs are wrong remember to like comment and subscribe thank you again to everybody who sent iguanadon toys and we will see you next time we would like to send a special thank you to these individuals who have gone above and beyond to support this show we could not have done it without you thank you [Music] you

Channel: Your Dinosaurs Are Wrong

Views: 692,127

Keywords: ydaw, your dinosaurs are wrong, steven bellettini, dinosaur, dinosaurs, dino, dinos, iguanodon, prehistory, prehistoric, jurassic, triassic, cretaceous, period, fossil, fossils, anatomy, skull, teeth, thumb claw, claws, hands, feet, restoration, paleo, paleontology, paleontologist, gideon mantell, waterhouse hawkins, crystal palace, sculpture, fossil bed, kid safe, kid friendly, child safe, child friendly, educational, science, tail, posture, mantellisaurus, monster, iguana, paleoart, talk dumb get the thumb

Id: u8ffPhdTk14

Length: 57min 32sec (3452 seconds)

Published: Tue Jun 01 2021