The Rough Life of SUE the T. rex

hello everyone and welcome to the rough life of sue the t-rex my name is tessa nelson and i'm an educator performer at the denver museum of nature and science and i am going to be your virtual host this evening as you watch the presentation tonight make sure to put your comments and questions in the chat as i will be monitoring throughout the program and we will share some of those questions during our q and a if you haven't been to the denver museum of nature and science lately we are actually we have the exhibit uh of sue the t-rex so please i'm going to put a link in the description come and check it out if you have time and without further ado i would like to introduce joe cerdich the associate curator of dinosaurs here at the denver museum of nature and science and he will introduce our presenter tonight yeah thank you i'm so excited tonight um first of all the exhibit is amazing so if you haven't come down to the museum to check it out uh it's only here for a couple more weeks through the 25th of april so make sure you come check out sue and not only is it the coolest dinosaur that ever lived the t-rex but it's also featuring a lot of our local dinosaur superstars uh like tiny the taurosaurus from thornton um at some of the first fossils you'll see from our highlands ranch triceratops discovery from two years ago and even some t-rex fossils from here in the denver metro area that we found in 1992 so get out see some of our local stars but really come for sue but tonight it's my pleasure to an honor to introduce this evening speaker dr jing may o'connor jing mei began her path to dinosaur super stardom in southern california where she began studying birds from the mesozoic which is the age of dinosaurs as part of her phd at the university of southern california she then spent the next 11 years at the institute of vertebrate paleontology and paleoanthropology also known as the ivpp in beijing china becoming their youngest full professor in 2015. this year in the midst of all this craziness with kovid zhing may returned here to the us as the curator of fossil reptiles at the field museum in chicago one of the most prestigious positions in the country her research explores the evolution of flight and dinosaurs the dinosaur bird transition and the evolution of modern bird physiology and has been published in many highly prestigious journals like nature science the proceedings of the national academy of science and many others and those su and t-rex may seem like a distant cousin of the many spectacular feather dinosaurs and birds that jeremy has described over the years xing mei and tsu have become really close friends recently in the galleries at the field museum so without further ado i'm absolutely thrilled dr o'connor agreed to speak with us tonight and let's hear her as we explore the rough life of sue the t-rex thank you so much for that uh wonderful introduction joe okay let me just do the awkward moment where i share my screen awkward moment and get us into okay great so um hello everyone and thank you so much for joining me this evening to celebrate one of the most iconic dinosaurs of all time you know one of the most beloved and awe-inspiring dinosaurs a dinosaur that needs no introduction tyrannosaurus rex and also talk about what we know about the rough life lived by one of the best t-rex specimens ever uncovered a t-rex named sue so here's sue in all her glory and her own private exhibition hall at the field museum uh she's quite big in case you hadn't noticed 40 to 42 feet long and 13 feet tall at the hip uh the largest terrestrial predator to have ever lived and i think it's you know every dream to be able to work on t-rex to actually contribute to the knowledge of this taxon is definitely something i never thought i was going to do until i started my job at the field museum until then as joe had mentioned i actually worked on the smallest theropod dinosaurs ever to live which are of course birds so basically i'm just warning you right now that throughout this talk i am going to use any chance i can to like sneak the odd bird fact in but of course we will focus on t-rex which was actually first discovered in 1900 while barnum brown a famous american paleontologist was digging for fossils in wyoming he found a partial skeleton and two years later while digging in montana he found a separate specimen the second specimen the one found in 1902 was described by his boss henry fairfield osborne in uh 1905 in which he erected the tax on tyrannosaurus rex the publication of which included this illustration that you see here which of course is this upright uh posture with his tail dragging on the on the tail this reconstruction that has dominated how we imagined t-rex for the first half of the last century now the specimen that was actually found earlier the one from my wyoming found in 1900 was also described by osborne a few years later and he named it dynamosaurus but then it was eventually realized that that was a junior synonym of t-rex so unfortunately that very cool name dinosaur name can actually never be used for any other taxon it's actually thought though that t-rex remains were found as early as 1874 in the form of some isolated teeth before we go any further what is a t-rex i mean we all know that t-rex is a dinosaur right but also what are dinosaurs dinosaurs of course are reptiles basically there are two major groups of crown reptiles one would be the lepitosaur morpho which are your lizards and snakes and the other is the archosaur morpho which are your crocs and your dinosaurs including birds so dinosaurs are archosaur reptiles within the diverse group that is the dinosauria all tasks can basically be split into two different groups one is the ornithiscio which means bird hip but ironically does not include birds and that's your horn ceratopsian dinosaurs your duckbill dinosaurs and your armored dinosaurs like stegosaurus that i heard so many people uh love and then your other clade is sauriscio which means lizard hips and that is also breaks into two different groups one which is the sauropoda which are your long-necked giant dinosaurs and the other group is the therapoda which are your bipedal primarily carnivorous dinosaurs including t-rex and also birds now within the therapeutic t-rex is a member of a more exclusive group called the solaris soria but actually t-rex is fairly closely related to birds in the grand scheme of the dinosauria uh t-rex and birds together form a clade called the tyranno raptora but t-rex is a is a member of a group called the tyrannosauroidia that i also will talk about a little bit more later t-rex is primarily found in the hell creek formation which is uh which records the last two million years of the cretaceous period it's a period referred to as the restriction so it's 68 to 66 million years roughly up right up until when the meteor collides with the earth and basically kills all non-avian dinosaurs the hell creek formation is found mostly in montana wyoming and north and south dakota but t-rex has also been found in the lance formation in wyoming and also i heard very recently in the larry lee formation in colorado the hell creek formation uh was deposited in a fluvial setting it just basically means it represents deposits formed in ancient rivers and it formed along the banks of the western interior seaway so during the middle cretaceous uh sea level was higher and so the middle part of the north american continent was flooded basically dividing north america into two different separate land masses however towards the end cretaceous sea levels start to drop again and this western interior seaway starts to recede uh but the hellcreek formation would have formed right about here i will talk more about what the hell creek was like 68 to 66 million years ago but first let's talk about sue su was found by a woman named sue hendrickson so obviously sue is named after sue hendrickson this is something that paleontologists will fairly commonly do will name really exciting important finds after the person who found them it's actually an interesting story how sue found sue uh she was working with the black hills institute prospecting on land that belonged to a rancher who had let them on to their land to look for dinosaurs and they had basically finished up they found some duckbill dinosaurs and they were ready to go and they get a flat tire so sue says while you guys are fixing the car i'm gonna go prospect a couple hills that we didn't get a chance to look at she's walking around the bottom of the hill and she sees broken fragments of bone and she looks up the cliff and she sees a layer with large bones sticking out and they take a look at these bones and they pretty much really immediately realize it's probably a t-rex and they you know took all these photos which are really good for us to have now to know exactly where it came from and they even like recreated the discovery of this fossil they immediately just tear this specimen out of the ground it took six workers 17 days to get the specimen out that is a incredibly short period of time if you've ever gone out and dug for dinosaurs it is a very painstaking process this little bit here uh that you can see covered in plaster was the bit of bones that we saw exposed in the previous slide and so they had to remove all the overburden all the rock that was on top of all this specimen like basically just remove half of a hill and uh you have to cap all the bones with plaster and then the specimen was was removed to the black hills institute to be prepared so the black hills institute is so stoked about this discovery right i mean this is a discovery of a lifetime they had found a complete skull they knew that they had a very complete animal so they're really excited and they're working on the specimen and then in 1992 like all hell breaks loose basically uh and a very dramatic story for paleontology which usually is not we don't have that much drama usually uh now really what happens from 1992 to 1995 should be the subject of its own talk and really it would have to be given by somebody who experienced this who lived through it i was like less than 10 years old at the time so i'm not really i've only heard some things through hearsay and i'm going to basically try to sum it up for you but if you're really interested there is a documentary that's all about this and i think pbs also did an episode about it so in 1992 the fbi comes into the black hills institute and they see sue and the local town folk are like no you can't take our t-rex and they're all protesting and the south dakota national guard has to come in and the irs seizes all this paperwork and a bunch of people are fighting over who has ownership pursue uh the rancher says it was his even though he was paid five thousand dollars for it but he's like that's not enough but it turned out the ranchers land well he was a native american a member of the sioux tribe so the sioux uh tribe also said that they were claiming ownership and also technically the land was being held in trust by the federal government so the federal government also claimed ownership so it was just a lot of drama in the end people from the black hills institute ended up going to jail for um for money laundering and a bunch of other things it was crazy but in the end the uh sue was awarded to the rancher whose land it was and he decides he's going to put the specimen up for auction and it goes up for auction at sotheby's and this distressed the scientific community because it meant that this specimen might end up in private hands it might be lost to science so the field museum kicked off a huge fundraising campaign in order to get enough money to to purchase the specimen in order to save it for scientific research they ended up getting a lot of money both from private donors but also from corporate donors like mcdonald's and also the disneyland parks and in the end they were able to get enough money and win this specimen at auction so in 1997 specimen comes to the field museum uh you can tell everybody was really excited about this because this was the end of a really long uh you know uh campaign uh financial campaign and the specimen immediately begins prep work in stanley hall and gets upgraded uh by their corporate sponsors and actually half of the prep was done at disney world in orlando and the other half was done at the field museum it took 10 preparators two years to prepare the specimen all of which was done under the public eye after the specimen was prepared it had to be mounted and finally in 2000 it was revealed to the public and they had this really fancy uh kabuki curtain drop which the field museum had to like practice like 100 times now it had always been the original plan for sue not to be in stanley hall which is the main hall of the field museum but to have her have its own exhibit so in 2018 they take the specimen down and because they're going to move it they also revamped the mount so the new mount in the new hall is much more sophisticated you can see that it doesn't have these um bars holding up the tail now here you have the 2000 and the 2019 mount now when i was a little kid i used to love to play those games like those pictures on the back of a cereal box like two pictures that are almost the same and they'd be like notice the differences so basically we're let's play this game together uh try to see how many different differences you can count in between the two of the old and the new mount and then i'm gonna go through each of them individually and you can see if you uh caught them all the first and the most obvious is that the 2019 version has the gastrelia added to it gastrelia are often referred to as belly ribs because they look like ribs and they protect the belly but actually they're not ribs at all they're dermal bones whereas most bones in the skeleton will first form through cartilage and then become ossified dermal bones will ossify directly within the dermis now dermal bone gastralia are present uh were used to be present in a large range of extinct uh fossil reptiles but today they're very rare they're only found in crocodilians and this weird not lizard that looks like a lizard called a tuatara it's also hypothesized that belly ribs form the bottom of the turtle shell now birds are living dinosaurs right but birds don't have gastralia they used to have gastralia during the mesozoic period primitive birds had a very small sternum sternum is where the flight muscles attach and flight muscles are really big in modern birds so as the sternum evolved to become bigger there was less and less room for the gastrulia so the gastro basket became much smaller and then was eventually lost in the one lineage of birds that makes it through the end cretaceous mass extinction now the fercula that was in the 2000 mount actually turned out to be a gastro fragment so it was actually part of those belly ribs so in 2019 the correct fricula or wishbone was put in place and because the correct fergular was much narrower this meant that the arms were brought in closer to the midline of the body the leg uh the left side the right leg in the 2000 mount was really strongly flexed almost to the point that sue was kind of kneeing itself in its own gut so the leg was straightened out a little bit in the 2019 mount and then finally the lower jaw was brought down a bit so that the gape or the mouth was open much wider simply because it looks cooler that way sue is this incredibly famous specimen and there's a number of reasons for this sue holds several world records the first is that it is the biggest t-rex that has ever been found now you're probably thinking hold up i am a you know a dinosaur amateur enthusiast and i remember reading in 2019 that a bigger t-rex was found a t-rex named scotty and you would have heard correctly but paleontologists like most people have this really weird obsession with size and so they're always trying to be like my dinosaurs the biggest and i found a new biggest dinosaur so let's evaluate the hypothesis that scotty is bigger than sue uh they basically argued that sue has a body mass sorry that scotty has a body mass of 8 870 kilograms and they compared this to what their estimate of sue which was 8 462 kilograms so it's roughly a difference of 300 kilograms but the way that they estimated the body mass of scotty and sue was using a single measurement which was basically the circumference of the femur however the circumference of the femur can be really easily measured ensue because it's really nicely preserved but not in scotty in fact that measurement had to be estimated so much that their estimate of the body mass of scotty being 870 kilograms had error bars of plus or minus 25 that is 2 217 kilograms compared to the purported difference of only 300 kilograms between these two specimens so the point is that scotty isn't really well preserved enough to say rigorously to say without a doubt that it is bigger than sioux certainly they are both very big specimens now if you want to understand body mass of an extinct animal you have to basically uh you what you have to do is estimate all the soft tissues that are not preserved it's not just the skeleton right and in order to do this you are making educated inferences because we don't have the soft tissue preserved we don't really know what it looked like we can make an educated guess about how big such and such muscle is but we really don't know which means that you have to have a minimum and a maximum estimate the reason i'm telling you this is just an excuse to show you this ridiculous figure which is one of my favorites and uh most people will rely on this particular paper and it came out in 2011 when they're talking about a body mass estimate for different tyrannosaurus rex including sue so here you have the minimum estimate and here you have the maximum estimate which i joke is like me before and after pandemic and uh the minimum estimate is that t uh that sue would have had a body mass of about 9502 kilograms versus an upper limit estimate of 18 489 kilograms however most scientists will just use the lower estimate as a proxy for the body mass of sioux which is about 20 948 pounds sue is the most complete t-rex that has been published to date the bones that are marked here in red are the only bones that were not preserved with this specimen so the t-rex specimen consists of 380 bones 250 of them are preserved in sioux that is 73 of the skeleton but the bones that are missing make up a small portion of the actual total mass of the skeleton so the sioux is 90 preserved by bulk now you may be thinking well when i look at the mounted skeleton i see a complete skeleton i don't see any missing bones so there are several ways in which we fill in the gaps in the specimen one way and the most simplest way is that we just carve pieces that would have looked like it for example this was probably done with the the pubis this part of the pubis that was missing for other uh elements that we have one side preserved but not the other what we'll do is we'll 3d scan the bone that we have and then we'll digitally create a mirror image and then print out that bone to fill in the other side so this was done for the foot and also for the hand and another thing that we'll do often do is and what we did for the missing thoracic vertebrae is you take the vertebrae that you do have preserved and you make molds and casts of them and you use them to fill in the gaps now one record that sue does not hold anymore is that it was at the time that it was sold it was the most expensive fossil ever purchased it exchanged hands for 8.36 million dollars which according to this new york times article was a staggering amount but if that was staggering then i would love to know what they thought about the whopping 31.8 million dollars that stan the t-rex was sold for late last year now this is actually the biggest problem that faces paleontology in america the commercialization of fossil fossil collecting means that uh scientific institutions can't compete with private sellers in order to purchase specimens and keep them for science i mean even getting 8.36 million dollars was a huge feat for the field museum there's no way they'd have been able to get together put together like 31.8 million dollars so now stan has been sold to a private uh collector it's been lost to science and so uh this is just a big problem because it also means with these type of price tags attached that if we would go up to ranchers and we say hey can we look for fossils on your land in the past they would have said yeah sure but now they'll you know a lot of uh ranchers will think twice and be like well i'd rather let a commercial collector on my land uh look for fossils for cut of the profit so it's a big problem but it's one that is rather unique to america i mean not entirely but there are a lot of other countries that do protect their um importance fossils for science now sue definitely gets more than its fair share of uh scientific research probably just because there's such a fascination with this amazing taxon and we've learned an enormous amount about tyrannosaurus rex over the past 115 years that we've known about this taxon one thing that we've been able to learn recently through the application of advanced scanning technologies like ct scans which are basically three-dimensional x-rays that allow us to see inside the bones is that we've been able to figure out pretty much exactly what uh t-rex brain would have looked like and it's actually proportionately larger than that of other theropods with the exception of theropods that are most closely related to birds it's like troadontids and dromeosaurids now what the brain shape also tells us is that t-rex was capable of enhanced coordinated rapid eye and head movements which would mean it would be able to track something that's moving rather quickly now using this same scanning technology we can also see what the inner ear was like and it tells us that t-rex had really good hearing when it came to low frequency sounds now another interesting thing about the shape of the brain is that the part of the brain that deals with smell is much more developed than in other theropods so compared to other therapeuts tyrannosaurus rex had a really good sense of smell now you're probably thinking what about this long-standing debate about whether t-rex is an active predator or whether it was a scavenger and you might be thinking aha a keen sense of smell this means that it was a scavenger not necessarily and probably not especially when taken in context of everything else that we know about t-rex instead it could be that a smell was important to t-rex simply because it hunted during a time when there was a limited amount of light like say in the evening or that uh smell that a keen sense of smell was important to another aspect of tyrannosaurus rex biology for example navigation or communication with other members of its species t-rex also has much better vision than other theropod dinosaurs with the exception of birds and its closest relatives it's also been said that t-rex can see better than an eagle and that the structure and size of its eyes are pushing the upper limit of what is capable in a terrestrial vertebrate now i just have to say that it's really hard for me to take anything that this paper says seriously simply because it has such ridiculous figures now studying the structure of the hip and the hind limb it has been inferred that t-rex was not a fast runner maximum speed of a full-grown t-rex was probably about 11 miles per hour the structure of the hip and also the limb proportions however do tell us that t-rex was very agile or relatively agile for its size now both direct evidence in the form of fossils bearing bite marks as well as digital analyses tell us that t-rex had an incredibly powerful bite the strongest bite force of a terrestrial animal ever it's estimated to be between somewhere and eight between 8 500 and 34 500 newtons so for comparison uh like a boxer's punch is about 5 000 newtons so we know from these analyses and also from direct evidence that t-rex was capable of biting through bone this is the hip of a triceratops and you can see that uh some t-rex just took a bite right out of it presumably through repeated biting so the sum of all these different inferences based directly on the morphology not only of an exceptionally well preserved specimen like sue but the cumulative uh you know collection of tyrannosaurus tyrannosaurus rex that have been collected over the past century tell us that it is most likely that t-rex was an ambush predator and the you know there's some interesting inferences that we can make for example the fact that t-rex has better vision than other theropods other large theropods probably hunted for sauropods which are relatively slow-moving animals but t-rex would have probably fed on things like edmontosaurus which is a duckbill dinosaur with complex social behaviors and also triceratops which is a pretty formidable uh prey because of its really large and uh sharp horns so it is thought that the increased visual capabilities of t-rex were to allow it to make a more precise strike from or you know from its ambush onto these relatively more dangerous prey animals now of course the fact that t-rex was a primarily an ambush predator does not mean that it did not scavenge uh surely it probably scavenged opportunistically if there's a dead animal there it's gonna eat it it's not gonna be like oh i'm too good for that and this also makes sense in what we compare with living animals so for example hyenas are often mislabeled as being scavengers when in fact they actually actively hunt at least 50 percent of their prey what about those tiny arms the tiny arms of tyrannosaurus rex have been the brut of numerous jokes uh like this one pictured here or t-rex can't clap its hands etc etc i'm sure you know what i'm talking about there are numerous hypotheses about the function of these ex proportionately very small forelimbs and these date back even to osborne who described t-rex originally he hypothesized that perhaps the tiny arms were for gripping their mates during copulation fancy word for sex um another hypothesis is that t-rex use its tiny arms for pushing itself up off the ground from a prone position uh also another hypothesis is that it used it for gripping its prey when it would have administered the fatal bite wound or even some uh researchers have suggested it was used its um short arms for slashing prey because you can see that these claws while you know proportionally short compared to the small compared to the body are actually quite large and quite sharp now in-depth studies of the forearm in t-rex indicate that it had very well developed musculature and we can tell this because they're little we can there are signs on the bone telling us where muscles would have attached and then therefore you can reconstruct the musculature and this shows that the forelimbs of a t-rex would have been like three to four times more powerful than that of a human also the bones are proportionately thick compared to other bones for their size which means that the forelimb was probably adapted for greater amounts of strain however the arm had very limited range of motion so the human forelimb has a 360 degree range of motion t-rex would have had a 40 degree range of motion that's very limited so it probably wasn't using its forelimbs for slashing so the leading hypothesis is that it used its prey it used its forelimbs to grip prey during active predation one of the coolest things i think about dinosaur biology is that you can cut a little piece of a bone and you can grind it down really thin uh to about like 30 to 70 microns and then you can shine light through it and look at it under a microscope and you can actually make a very accurate estimate of how old that dinosaur was at its time of death and this is because dinosaurs don't just grow throughout the year without stopping they grow for a certain part of the year and then a certain part of the year they don't grow and during this period that they're not growing inside the bone a line is deposited and this is referred to as a line of arrested growth or sometimes just a cyclical growth mark and the spacing between these growth marks tells you how much that dinosaur grew within a certain year and if you look at all these different t-rex specimens you don't see a very even spacing and you don't see a pattern and what this tells us is t-rex was capable of growing more or less in a given year depending on whether or not resources were abundant now once growth ceases basically the dinosaur reaches its maximum adult size these lines become very closely spaced just stacked right on top of each other like you can see here and that's when you see this when you cut a dinosaur bone you know that the dinosaur is mature that it's full grown now in looking at the bone histology of t-rex sue in particular we can tell that sue was about 28 years old when it died that's one of the oldest dinosaurs that's been recorded and also that it reached full adult size at about the age of 19 or 20. now this is a rib that was studied uh you know over 15 years ago however more recently a a bone core was taken out of the femur because the femur is the best bone for doing this type of research uh you're probably like oh my god you put a hole in it uh don't worry what we do is we cast and we mold and cast the piece that we take out and we plug up the hole so if you see the specimen on display you're not going to see a hole now this is the femoral section it doesn't have the lags marked but if you have a sharp eye you can probably see one here and here and here and then you can see in the outer portion of the bone you can see the uh very closely spaced lines telling us that sue telling us what we already knew that sue is a full-grown dinosaur t-rex would have hatched at about the size of a small turkey and then within 20 years grew to weigh over 20 000 pounds so during those 20 years of growth of course the skeleton is going to increase in size but in addition to those uh increases in size there's also changes in proportions and also the morphology of the animal so this is referred to as ontogenetic changes and it also happens in humans so for example if you take a baby and you scale it to be a six foot tall baby like the size of a full-grown adult male that's not what an adult male looks like right it's you know it doesn't look like a giant baby there are proportional changes that happen during the ontogeny of humans and the same thing is also true of t-rex because of these anti-genetic changes the first juvenile t-rexes that were found were actually thought to be a totally different taxon so you may have heard of this small tyrannosaur relative called nanotyrannus nanotyrannus was just a skull which didn't uh and it was a very different looking skull than what we see in t-rex but then another specimen that was more complete called jane that was also referred to referred to nanotyrannus also preserved post-cranial elements and these post-cranial elements allowed us to do histology like we saw in the previous slide and using histology it could be shown that jane was not full-grown you didn't see those closely packed layers in the outside of the of the bone cortex and and you could also see that jane was about 15 years old however even though jane is 15 years old it was about half the length of a full-grown t-rex like sue this means between the age of 15 and about 19 or 20 t-rex has this massive growth spurt where it grows exponentially and then reaches this full-size adult at the round you know at the round age of 20. what this means about t-rex biology is that basically t-rex forms two different size classes you have your younger smaller t-rex and you have your bigger giant t-rex and because they're so different from each other not just in size but also in proportions and morphologies they have essentially very different lives they're feeding on totally different animals for example so a younger t-rex would have had proportionately longer limbs both legs and arms so maybe the arms had increased function possibly when it was younger but the fact that had longer legs and also a smaller trunk suggests that younger t-rex was more agile but bite force also increases with size so a young t-rex like jane would not have been capable of crushing through bones so the feeding behavior also would have been totally different one of the biggest controversies in t-rex biology is whether or not t-rex had feathers so the field museum reconstructs t-rex as naked without feathers whereas if you have been to the american museum of natural history and seeing their tyrannosaur exhibit you'll see that they reconstruct t-rex as feathered now which reconstruction is correct the short answer is we don't know however i am going to outline the evidence and to explain why this is a controversy at all in 2004 a basal tyrannosauroid so a primitive member of the same group that includes t-rex named delong was found in china that preserved these proto feathers now they don't look like a feather that you would see in a modern bird but these are the primitive precursors to modern feathers and they're very simple structures they're monofilaments so these proto feathers are sometimes referred to as dino fuzz now d long is very small it was less than six feet long so it was thought that okay maybe small primitive tyrannosaurus had feathers but then eight years later you tyrannous was discovered also preserving dino fuzz but you tyrannus is 30 feet long so that's like 75 percent the length of a t-rex this is a big tyrannosauroid and it still has feathers now the reason we don't just automatically say okay t-rex had feathers is because of how proportions change when you become really big so as you increase in size your surface area is only increasing at a square however your volume that is encased by the surface area is increasing at a cube what this means is that when you're very small you have a lot of surface area for a very proportionately small volume versus when you're really big you have a proportionally small surface area for a proportionately very large volume now your surface area is how you interface with the environment this is where heat transfer occurs so basically when you're really small you're losing a lot of heat because you have a lot of surface area and it's more difficult to keep yourself warm but when you're really big you have the opposite problem so we don't really argue about juvenile t-rex most paleontologists agree that a juvenile t-rex was probably covered in diet of us even though we don't have any direct evidence of this however people argue about adult t-rex and about five years ago a study was published with a very nice specimen of t-rex that preserves several patches of skin and this included on the neck and on the back and the tail and also some other specimens preserved a little patch on the leg here and there so this study argued that based on this evidence you could you could say that t-rex did not have feathers however i disagree with that conclusion and in order to make my argument we're gonna do a case study looking at another dinosaur named cetacosaurus now cytakosaurus is a basal relative of triceratops it's found in the early cretaceous of asia and in china alone there are thousands of specimens of statakosaurus and these are very complete most of them are more complete than sioux however even though you've got thousand specimens only one preserves evidence that the tail had this weird patch of proto feathers elongate bristle-like proto-feathers if this specimen looks familiar to you that's because it was in the news fairly recently maybe late last year because this is the first dinosaur ever to preserve uh the soft tissue of the cloaca basically uh reptiles have one hole for all the holes and it's called a cloaca anyways but uh the point is that you know you have so many specimens and only one captures this morphology so it just shows just how rare soft tissues are and even if this specimen if the tail or just this part of the tail hadn't been preserved then we wouldn't know about these feathers or these protofeathers another thing is that these protofeathers don't look like they have some kind of function they don't look like they're for defense or anything they look ornamental and speaking of integumentary or feathery ornaments we see numerous structures like that in living dinosaurs you know picture a peacock or even the sexual dimorphism you see in a duck birds have tons and tons of bizarre and beautiful ornamental structures that show just how important sexual selection has been in shaping the feathers or protofeathers of dinosaurs and this is something we also see even in the mesozoic and the early cretaceous birds that i study we see a lot of sexually sexually driven feather morphologies so i would argue but it's just a hypothesis that t-rex probably had some feathering even as an adult but i don't think it would have looked like it's illustrated here i think that's a little bit more uh too extensive i would argue that t-rex had a very small patch of ornamental feathers obviously not looking just like that but you get the gist of what i'm trying to say and it is also possible that these this small patch of ornamental feathers possibly was only present in one of the genders and it's also possible that these feathers were only present during the reproductive season and that they were molted during the non-reproductive time which may also be why it's extremely difficult to find these structures preserved in the fossil record now that we know a bit about what sioux was like and what t-rex biology was like let's look at the world in which t-rex lived in north america in the late cretaceous roughly 68 to 66 million years ago so i mentioned that the hell creek was deposited in river channels so this area would have had extensive river channels which of course are changing through time and sometimes as parts of the river get cut off from the main river flow some peaty swamps would have formed and also where these rivers met that western interior seaway that i mentioned earlier we would have had deltas for me because t-rex is so fascinating a lot of prospecting and collecting has been done in the hell creek it's also a very rich deposit and as a result we have tons of fossils that really help us to understand just what you know the rest of the flora and fauna that accompanied t-rex would have been like so let's start with the plants about 90 of all plants that have been recovered are angiosperms meaning flowering plants now why this is interesting is because flowering plants don't evolve until like the latest giraffe latest jurassic early cretaceous but by the late credace they've already taken over uh these uh carista deer reptiles which are uh arcosauromorphs and uh but they went extinct in the myocene so you wouldn't really uh be too familiar with them but also crocs that have been collected from the hell creek deposits tell us that the environment was subtropical because crocs like this can't don't live in colder environments again just so many fossils have been collected all sorts of different fish paddlefish scars you know soft-shelled turtles small mammals like delphidone as well as charismatic dinosaurs that people are very familiar with like pachycephalosaurus and kylosaurus they all come from the hell creek formation also some dinosaurs that are more recently discovered that are maybe a little less familiar but also still very interesting like anzu which would have been feathered like it's depicted here it's a close red relative of oviraptor we also know from direct evidence that i hinted at earlier that t-rex would have fed on dinosaurs like edmontosaurus which is a hadrosaur or the so-called duck-billed dinosaurs and triceratops and there's even one specimen of edmontosaurus that has what has been interpreted as a t-rex bite mark on its tail that healed and if correctly identified this would be evidence again supporting the active predation hypothesis because this would be an edmontosaurus who you know got attacked by a t-rex but lived to tell the tale living also in the hell creek fauna were large flying reptiles uh the this picture here is quetzalcoatlus but actually which is the largest um flying reptile of all time the largest pterosaur of all time but the uh pterosaur remains that were found in the hell creek actually are smaller relative of quetzalcoatlus and also i am totally shocked and dismayed that there are no birds in this mural despite the fact that there was a diverse avi fauna living in the hell creek formation i know i'm the only one who cares about uh mesozoic birds but the reason i am going to go into this in a little bit more detail is because uh in the hell creek formation there is an anti-ornithine bird called av saurus it's a member of a diverse group of enantiomeric themes found only in north america that's not north america and south america called the av soroday and there is an av sword named gediya which myself and some colleagues named in honor of the late mike getty now sue was the apex predator in the hell creek fauna it was you know you imagine that it is the terror of all animals that are living in this ecosystem however but the really point of this talk is to say that you know life isn't easy even when you're the apex predator sue is so well preserved and so complete that it reser it preserves multiple uh evidence of all these different injuries and ailments and sicknesses that tell us at the time of death sue was hurting so i'm going to go through all these different injuries starting with the most obvious which is on the right side of the body you'll see several broken ribs and if you look at these ribs closely you'll see that the bone surface is kind of bulbous around the breaks this tells us that these breaks had healed at the time of death on the same side of the body if you look at the femur i'm sorry if you look at the humerus and you look closely on the medial surface you're gonna see this deep pit that's not supposed to be there that avulsion pit is evidence that a muscle that attached there probably the triceps muscle we're not quite sure it was engaged in such strenuous activity that it ripped off the bone that sounds painful right but again this injury so shows evidence that it had healed there's a spur of bone coming around this injury that shows that this um yeah that this wound was healing itself now on the same side of the body but i don't have a picture of it so you're going to have to go see the specimen for yourself the scapula coracoid also looks abnormal like evidence of trauma now if you look at the scapula coracoid on the other side where these two bones meet there's a very nice very clean suture but if you look on this side uh that is close to the injured humerus you're gonna see that the suture is not clean at all and that there's like a big lump growing on the surface of scapula coracoid so this is also considered to be evidence of trauma and the fact that these three injuries all occur on the same side of the body suggest that it is possible that they all occurred in the same traumatic incident it is hypothesized that this happened while struggling with prey but again we don't really know for sure if you look at the hand on the same side of the body because remember the hand on the other side was actually not preserved and you look closely you'll see that the articular surfaces between the metacarpals are looking a bit rough now the um what we're looking for in particular is is covered by the bracing but if the metal braces were taken off you would see on the articular surfaces eroded pits and this is a it clear in sign of gout so gout is when you have too much uric acid in your body either because you have a very unhealthy diet like say henry viii or kim jong-un or it can be because your body has some problem and it can't get rid of uric acid of course like i mentioned this obviously affects humans but it also afflicts both groups of living archosaurs crocodilians and birds so therefore we can infer based on the phylogenetic phylogenetic position of dinosaurs that this also probably would have afflicted dinosaurs and this is a very painful condition by the way if you look towards the end of the tail you'll notice that two of the vertebrae are fused together and looking a little bit funky this has been interpreted as evidence of arthritis that resulted from an injury but more recently it's been thought that perhaps this is a sign of bone infection which is also seen on the fibula and if you look at the fibula on the other side it looks very nice the bone is very smooth but here on the left hand side of the body you have um you know this bonus surface is very bulbous and rough so at first it was thought that this was a healed break like we also saw on those ribs but recently the fibula was taken out and it was high resolution ct scanned and no fracture was found so then it was reinterpreted as simply evidence of bone infection now bone infections in living dinosaurs like this are mostly caused by some kind of trauma that exposes the bone and allows bacteria to get in there and infect the bone so this also would have been something that was very painful possibly the most perplexing of the different ailments that we find evidence for on sue are these bizarre holes on the posterior half of the lower jaw now some of these holes like this one back here are supposed to be there they're part of the anatomy of t-rex but most of these holes like here here here here here are not supposed to be there they're not normal anatomy of a t-rex lower jaw however these holes are found in lots of t-rex specimens so whatever caused this is something that was that commonly afflicted t-rex now originally it was thought that these were bite marks because theropod dinosaurs in general like to bite each other in the face and but usually when you find bite marks that are very clearly un-irrefutably bite marks they're usually on the front end of the skull and also usually the puncture wounds you can match up to a certain portion of the tooth row in either the upper the lower jaw and you'd be like oh yeah for sure that's a bite mark right now these holes don't match up the pattern of teeth in a t-rex at any age or any part of the jaw so maybe they're not bite marks so they were reinterpreted as being evidence of a bacterial infection however people later pointed out that that bacterial infection that supposedly formed those holes is not found in living archosaurs it's only found in mammals so it's unlikely that it would have affected extinct archosaurs if it doesn't affect living archosaurs so the most recent interpretation for these holes is that it's a result of a protozoan infection and the most likely candidate for this infection is a protozoan called trichomonas gallinae fun kind of gross fact uh trichomonas vagilis causes an std called trick is the same genus so technically if this hypothesis is correct you could say that sue the t-rex had trick now this protozoan when it affects extant archosaurs when it exp affects birds it forms an illness called fraunce and it causes lesions on the posterior half of the lower jaw same as we see here in sioux when birds get frowns they actually don't die from the infection the infection causes their throat to swell up and they actually end up starving to death which sounds horrible but uh this has been suggested to be possible it has been doesn't be suggested that this may have been the cause of death in sioux that perhaps sue starved to death because it had this throat infection however if you look at the holes very closely it had long been noticed that these holes show signs of healing these little bone spurs that you can see extending into these holes are indicators that the bone was re-growing so it doesn't seem likely perhaps that sue died from whatever caused these holes and the fact is that researchers are still not convinced that these holes may were actually caused by this protozoan infection so uh fairly recently i actually tried to re-study these holes to see if we could get some additional evidence to provide a clarified interpretation what i didn't know is that if you ask to open the sioux skull case you will trigger trigger a media feeding frenzy so now now i'm i'm warned another possible cause of death that you may have heard of is that sue died in mortal combat with another t-rex now the sioux that is mounted on the skeletoo skull that is mounted on the skeleton is not the original skull the original skull is kept in its own case so they can be much it can be easily accessed for research also because it's a bit deformed so this goal that is mounted is a retro deformed version of the skull and the skull is you know it's squished in some areas and in other parts the bones are broken so at one point the breaks and the bones were contin were it were interpreted as evidence of you know a bite wound by another t-rex however more recently it's been reinterpreted as postmortem trampoline meaning after sue died some other dinosaur walked on the skeleton before it was buried and caused some of this breakage the most recent hypothesis for cause of death of sioux was is actually sepsis due to these bone infections so sometimes when your body is fighting off an infection it will turn on itself and will cause sexist which can cause septic shock and this can cause death so it is possible that that is why uh sue died because we see two different parts of the body that were infected uh that were clearly uh experiencing chronic infection however the fact is we're probably just never gonna know how sue died so this is a summary of our current understanding of what we know about tyrannosaurus rex and also what we know in particular of this wonderful specimen sue however i do want to make the caveat that we are always going to be learning new things and reinterpreting things that we have previously described as we develop new methods of investigation that provide new forms of data and of course also when we find new specimens that shed light on something that we didn't previously fully understand i think it is clear that research on sue and in t-rex in general will never cease as long as there's humans around to have their imagination captured by this awe-inspiring taxon thank you so much for listening and i look forward to your questions thank you so much dr o'connor that was so cool that was like the coolest thing ever thank you so so so much um we do have so many questions in the chat from interested folks and if you do still have questions go ahead and put them uh in the chat and i will continue to ask them so to start off um we have josephine asked at the very beginning do you know what was the last dinosaur alive well i mean there would have been a lot of dinosaurs alive together at the very end cretaceous so i think we can't really say one in particular uh but uh t-rex definitely would have been among the last dinosaurs alive but i also want to say that dinosaurs aren't dead you know dinosaurs are alive and well there's over 10 000 species of living dinosaurs that is more than double the number of species of living mammals so i know we say that the mesozoic was the age of dinosaurs and the cenozoic is the age of mammals i say it's still the age of dinosaurs absolutely it's always good to think when you get a bucket of chicken you're like i'm eating a dinosaur emma just added on to a question from ben and sue from earlier which is what what is whose gender is who male or female do we know we don't know so uh because it has is named after a female who found it i sometimes even myself will slip up and uh use say she i think the official party line of the field museum is that we're supposed to use they whoops but um i prefer it because the fact is that um you know gender and actual sex are kind of two different things how you identify versus what your actual biological gender is in the case of t-rex it really just would have been a case of biological gender not identification there are some ideas that you know because there's a lot of different t-rex skeletons and some of them are really like beefy and some of them are really gracile so it has been hypothesized that the gracile ones are males and the beefy ones are the stout stocky ones are females and sue is one of the stocky ones so it's possible that it was female but honestly we really don't know um kind of on the subject of just like what do we know how about the color of sue's blood was it red do we have any idea i would okay oh goodness okay well i think it's always really important for scientists to admit when they are not sure about something so i'm not sure but i would guess i would wager that it most likely would have been red when it contacted with oxygen same as our blood and all chickens and stuff yeah it's always fun you're like ooh so many things that i don't know science is cool natalie was wondering more about t-rex adolescence given that there was a huge jump in size it seems like teenage t-rexes must have had quite an appetite do we know were they hunting on their own at that point or do you think that they were still kind of in family units again it's something we don't really know but there is evidence that tyrannosaurus moved in packs there have been some trackways that show several different individuals of course it's always possible that those tracks like one t-rex came along and then like an hour later another t-rex came along so you can't really say that that's evidence of uh gregarious behavior but it is it is entirely possible especially if you think about apex predators alive today for example lions right adolescent male lions will hang around together in packs and groups before they like become you know their like own independent dominant male so it is possible that uh juvenile or younger t-rexes may have cooperated together but we really don't know something to figure out in the future danny who is seven years old is wondering did sue eat other t-rexes or did sue eat smaller plant-eaters there is evidence of tyrannosaur cannibalism yeah unfortunately and also young t-rex had a very high mortality rate so they say that during the like 60 percent of t-rex died within the first year of their life which is pretty sad but uh you know we again don't have any t-rex eggs and so we don't really know but we're making inferences on what we know from other dinosaurs we guessed that a female t-rex would have laid maybe about 20 eggs at a time so there would have been a like the population would have drastically become smaller as you increased in age um they did eat herbivores as well right yeah yeah sorry i forgot the last half of the question i got so excited about cannibals i i'm feeling that vibe i totally got you dr o'connor um scott is wondering how common are t-rex finds across the u.s and across the world are they pretty restricted to montana or are they found in other places well sue was found in south dakota so most of the discoveries are from south dakota wyoming uh north dakota and also whether i know there's one i'm forgetting no yeah so montana's wyoming north and south dakota but i i you know of course there are smaller amounts or more rare discoveries that have also been made in colorado and i think there also are some more rare fragmentary remains that have been a little bit south of these other main deposits but a vast majority of specimens are found in the hell creek which are in these main four states that we talked about but this is just t-rex of course there's other tyrannosaurs found in other places sorry someone was wondering about that too what what uh what defines a tyrannosaurus what are some other kind of awesome kinds of tyrannosaurs um awesome well okay so i guess depending on how you're uh defining first like a tyrannosaur are you talking about a tyrannosauroid or a tyrannosaurid or tyrannosaurin or tyrannosaurus each one has their own definition and also these definitions are always changing because we'll find some different specimen that's like oh that feature now we know it's part of a more inclusive clade so the definitions are constantly changing uh some other cool tyrannosaurs uh in addition to the ones that i talked about with the feathers from china like uh you tyrannus and dilon there's also guanlong which has this like crazy crest on its face also um gorgosaurus i think is one that people are pretty familiar with or i'm going to butcher the name i know das plito saurus uh anyways but yeah there's quite a few also ao tyrannis from the uk uh i think from the early cretaceous yeah there's there's there's quite a lot and i've also if you look at um like rates of discovery like within the last 20 years there's just like a ton of tax that have been discovered cool um mason who is nine years old is wondering what the oldest dinosaur was which i guess could be interpreted in two ways just what was the first dinosaur to appear on the planet and then also sue seemed like she was getting are they sorry it uh was getting pretty old um do we know kind of the lifespan of dinosaurs um well so with different dinosaurs i know like okay so first you have to have a lot of specimens in order to figure out and you have to cut a lot of specimens in order to figure out exactly what the lifespan would be this has not been done for many dinosaurs it's been done for my asaurus uh and it's been done for t-rex and i think really those are the only two uh and i honestly i've my brain is not remembering how long a myosaurus lives but yeah t-rex would have lived about we think 30 years max if you're also the question could be what is the oldest dinosaur in terms of the geologic record which actually how i interpreted the questions i'm going to answer it anyways um it's about 243 million years of old specimens of a pro sauropod so there are the primitive relatives of these giant long neck dinosaurs but prosauropods actually weren't quadrupeds they were like kind of bipedal and they were much smaller and it's a specimen called yeah okay i'm gonna butcher the name oh goodness that's so embarrassing but it's from uh madagascar but uh that was found i think fairly recently before that we thought the oldest dinosaurs were things like eo raptor which were about 228 million years old from argentina great um i want to call out the fact that it is 801 so our program officially ended a minute ago if you don't mind there's a couple of questions left but if you have to go any anywhere or attendees if you have to go anywhere thank you so much for joining us it was really really really great to have you here um thank dr o'connor yeah i'm happy to take a few more questions great and i will respect your time we'll try to we'll try to end soon thank you so much for staying on and for answering your last questions um cam is wondering you mentioned that t-rexes are suspected ambush hunters and you've also mentioned that there's t-rex cannibals so there was some t-rex t-rex interaction uh they are wondering might they have ever hunted together or teamed up on hunts again it's possible and it does uh make sense somewhat especially because they have this enlarged brain which means that you can have more complex social behaviors but uh there isn't any that i know of very strong evidence to indicate that at this time thank you um let's do two more questions and then we'll close so someone was wondering i really loved uh your hypothesis about the feathers used for uh for kind of sexual mating dances just like the birds of today that was awesome uh someone is wondering just do you have any guesses about colors if you were to imagine what color t-rex feathers were what would you imagine well i yeah i mean i would imagine something flashy right because with modern birds that have very flashy plumage they're really running the risk that they're going to make themselves more obvious to predators right but t-rex doesn't have to worry about that so i mean fancier the better right uh you know so i mean well it's one hypothesis anyways they could simply have competed you know feats of strength or something that's kind of one hypothesis i like to think about with the tiny arms i'm like maybe they're like whacking each other with them but anyways i think that they probably would have had pretty colorful feathers we have evidence from the early from yeah the late jurassic and early cretaceous of uh structural colors which are those um colors so there's different forms sorry i'm going to nerd out on colors because it is my area of expertise but like if you look at all the colors on a peacock tail those are structural colors so basically within the feather there are little air pockets that reflect refract light and then make all these really brilliant colors however now that i'm thinking out loud uh we don't see evidence of those kind of fancy colors in the more primitive protofeathers like t-rex had so let's just be more conservative and say that it probably would have had like reddish colors black and white like maybe gray yeah pretty boring palette now they think about it darn oh that's a shame it was very exciting to think about air pockets or refraction where'd you get your hopes up that's i mean red with black and white you can imagine a pretty cool dino mohawk yeah totally totally um and then for our final question uh dinosaur sleep how do you think dinosaurs managed sleeping in such a such a kind of vicious world well i guess it would have been different depending on each toxin because dinosaurs are so diverse and they have so many different body types and habitats and some were solo uh some were you know gregarious so i imagine that it would have been probably pretty similar to what we see in living birds you know like for example living penguins that are very gregarious during their breeding periods you know you have the ones on the outside that are just like you know they're gonna set up the alarm if anything happens right and you're safer on the inside maybe you're constantly changing um otherwise you're gonna be you know trying to hide yourself when you're sleeping that's also something that animals will commonly do it's also possible that a lot of animal dinosaurs were nocturnal so they could have been hiding during the day and sleeping and more active during the night this has been hypothesized based on eye morphology for some dinosaurs so um yeah i guess it would have been very different depending on the dinosaur um but uh very carefully if you're one of the small ones who gets picked on by the big ones awesome well thank you very much i really can't thank you enough for that incredible presentation it was really really really great um and if you're interested in the subject on april 13th our own dr joe cerdich will be presenting on sue's local friends 150 years of dinosaur discoveries in the denver basin i have a link to that in the chat but with that thank you again and i hope everyone has a great night bye-bye thanks so much bye

Channel: Denver Museum of Nature & Science

Views: 113,890

Rating: 4.8457751 out of 5

Keywords: DenverMuseumOfNatureAndScience

Id: BUEp8tNJxbE

Length: 66min 27sec (3987 seconds)

Published: Thu Apr 15 2021

Reddit Comments

[u/Prs_mira86]

Very interesting stuff. Paleontologist jingmai said that Sue is probably still the biggest Rex estimated at 20,948 pounds or 10 tons!

[u/DaMn96XD]

Really sad story. Inflamed ankle, trichomonosis and all. And even after that when Sue had starved to death, something trampled and flattened her head.