The Life and Times of Tyrannosaurus rex, with Dr. Thomas Holtz

okay great so I'm so glad to see so many dinosaur fans here um anyone here like t-rex especially among the young people alright good yeah I've loved t-rex since I was a little kid I'm told that when I was really small I told my parents that when I grew up I was going to be t-rex and they told me that wasn't going to happen so apparently I said okay then I'll work on them and so because of that I actually stuck with that you know whether whether this is stubbornness or refusal to grow up or if those are actually mutually exclusive I don't know but yeah I work on Tyrannosaurus and and so on I'm here to talk about Tyrannosaurus Rex but also some bigger aspects of the nature of science and that's one of the best things about dinosaurs is dinosaurs are in some ways the ambassadors of science because it can help the public and especially the young members of the public understand that science isn't about knowing things it's about learning how to learn about things how we answer questions about the natural world and I think far too often people think of science is just a body of knowledge you have to master but it's through science that we're going to answer the problems that the world faces and that's sort of the contribution that dinosaurs can make that we can teach young people and older people to to think about scientific approaches to life and to the universe um to learn about amazing things like well it's like Tyrannosaurus so some of the main topics I'm going to cover is a little bit of introduction of Tyrannosaurus Rex and something about its discovery I don't need to introduce too much about Tyrannosaurus Rex it's the one it's the one species that everyone gets its name right people for example think they know our species but people lost a homo sapien it's not it's almost APNs that's not a plural if that the NS ending is just like an ing ending in English so Homo Sapien would be like thinkin man but so then I'm going to talk about how we try to infer about the lifestyles of creatures where you know we can't be David Attenborough we can't go out and watch the animals in the field anymore they're not doing too much anymore so we've got to infer their life habits by other types of evidence and then a particular field of research that's I was involved with and that's a very growing field which is tracing the origins of Tyrannosaurus and it's kin so Tyrannosaurus is a North American dinosaur these dots represent the range of t-rex in the western interior of the United States from rocks with wonderful names like Hill Creek and lance and Frenchman and scholar and so forth these are rocks from the very end of the age of dinosaurs out west now the places that Tyrannosaurus lived this is a picture of North America a reconstruction of the map of North America this is actually before t-rex lived I'll show the next slide will be segwaying into when it lived was at a time when immediately before t-rex sea levels were much higher than present so if you were to trampy transported back in time as a time traveler you could have taken a boat from the Gulf of Mexico and sailed over Texas Oklahoma Kansas Nebraska the Dakotas the prairie provinces all the way to the Arctic Circle and never see land but that changed at the very end of the age of dinosaurs as sea levels dropped and Tyrannosaurus lived during this interval when sea levels were dropping the coastlines were moving inland and Tyrannosaurus moved inland with it it's not inconceivable that someday we're going to find Tyrannosaurus Rex in the eastern half of North America unfortunately we don't have terrestrial rocks of the right age at the moment to to recognize that people have known about Tyrannosaurus Rex since the beginning of the 20th century well technically since the end of the 19th century there were some fragmentary specimens found in the initial burst of discovery of dinosaurs in the late 19th century but a good pick sure of it didn't develop until the dawn of the 20th century from expeditions of the American Museum of Natural History and the Carnegie Museum in Pittsburgh uh and in 1905 this animal was named by Henry Fairfield Osborn of the American Museum of Natural History in New York given the name Tyrannosaurus Rex which remains one of the best names in in biological nomenclature because it's a really evocative tyrant Lizard King I mean that's a you don't get cooler than that actually you almost do in the same paper Osborn named Dynamis Oris imperio --ss the Imperial dynamic reptile but that turned out to be a second specimen a Tyrannosaurus Rex so it's the same animal so this was the initial attempt to reconstruct what it looked like a year later the fossils had been better prepared out and they're beginning to focus in a little bit more it's kind of tubby looking in this reconstruction but even at that time Osborn was aware they were onto something new carnivorous dinosaurs weren't new they had been known since the earliest days of the 1800s 1820s when Megalosaurus was named arm and even big carnivorous dinosaurs weren't weren't new Megalosaurus was an animal that ran about 20 feet long or so Allosaurus had been discovered in the 1870s 30 feet or so Tyrannosaurus though was even larger still it dwarfed those previous discoveries and as even better specimens were found people got a much better sense of what it looked like this was the the classic mount of Tyrannosaurus Rex at the American Museum recently recently nineteen nineties remounted it's the one on liked eye and if you um if you're if you've ever seen the Jurassic Park movies or books toys or video games or whatever the franchise is now you've seen this specimen that's part of the logo so Tyrannosaurus became an iconic dinosaur in the early 20th century it made its way unto cartoons comic books novels early stop-motion animation movies and so forth and it's really well known to people but not always well-known are certain aspects of it there's misconceptions that have acquired the Tyrannosaurus is acquired a lot of people think that Tyrannosaurus was the largest dinosaur it wasn't there it was big as a meat-eater goes but it was dwarfed by many of the plant eaters in fact it was dwarfed by at least one plant eater in its own environment this is a brand new mount in in Dallas of t-rex that's an adult t-rex next to the largest animal in its environment here they are in silhouette is a plant eater called Alamosaurus Alamosaurus has actually been known for quite some time but we didn't know how big it was because it turned out the first specimens found were not fully grown and new discoveries of it show that Alamosaurus is as big as the largest dinosaurs known elsewhere in the world so we now see that North America now has a dinosaur that rivals the giants of Argentina and of China so t-rex is big but it's not the biggest dinosaur nor is it even the biggest meat-eating dinosaur there are other flesh-eating dinosaurs that were at least as large or larger among them are giant Allosaurus such as Giganotosaurus and Carcharodontosaurus and mapusaurus a cluster of Sharptooth shark-tooth dinosaurs the carcharodontosaurus and another group that's larger still the Spinosaurus although they kind of cheat because the Spinosaurus although they ate the flesh of other dinosaurs we have digested remains of dinosaurs in their bellies they also a big fish so they're sampling from various parts of the ecosystem but even if it's not the largest Tyrannosaurus is one of the most impressive and it is I was here so here's a reconstruction of Carcharodontosaurus facing off with Spinosaurus these guys are actually contemporaries so it was an environment where we had at least two t-rex sized predators in the same environment so t-rex is the one in purple in here and we see it's got a lot of rivals among other giant meat-eaters and a giant plant eating meat-eating dinosaur yeah okay so nature is what nature is and it doesn't have to obey our rules and our names so just like today we have pandas which are members of a group called carnivory so we have bamboo eating carnivores so - in the age of dinosaurs there were plant eating members of the meat-eating dinosaur group but Tyrannosaurus was the largest of its own particular group so now it shifted color to red t-rex is the largest of its own family of dinosaurs and by a bio bio margin there so that's Tyrannosaurus Rex this is in fact the original specimen now at the Carnegie Museum recently remounted into this nice pose and it's just one of a cluster of closely related forms including things like Tarbosaurus Daspletosaurus gorgosaur's albertasaurus and alioramus and except for all your Amos which is smaller and it's got these little horns down its nose there's about five people in the world who could tell these guys apart or care but they're all really spilt on the same body plan it just t-rex is the heavy SUV version and some of these other ones are you know the sports car version and the you know whatever the minivan it's all variations on the same basic body plan and collectively they're called the Tyrannosaur it a so that's simply the old taxonomy it means a day is of the family of so of the family of Tyrannosaurus or Tyrannosaur it'd if we're talking about it not in its formal Latin phase so the tyrannosaurids taranis or today are actually late comers in the history of dinosaurs so the oldest dinosaurs are down around here near the transition between the middle triassic and the Late Triassic now let's just say we so the oldest dinosaurs around here classic dinosaurs like Stegosaurus and Allosaurus and Brachiosaurus are here in the Late Jurassic t-rex and company are towards the end the great extinction is this red line right here and we are at the top of this diagram and something to consider is we are closer in time to Tyrannosaurus Rex the Tyrannosaurus Rex was to stegasaurus more time separate Stegosaurus and t-rex and separates t-rex and us so there's not just one world of dinosaurs but many worlds of dinosaurs and for most of that dinosaurian history it was the Allosaurus and the Megalosaurus like spinosaurus spinosaurus that were the largest body predators tyrannosaurids were late comers in that history they also had sort of a limited range so t-rex and its can the Tyrannosaurus were limited to this part of the world Western North America extending over the bering land bridge to eastern and central asia china mongolia who's becca stan and so forth down into Southeast Asia separated from the rest of the North America by the shallow sea way except possibly up at very tail end and separated from the rest of Eurasia by another shallow Seaway and totally separated from the southern continents so Tyrannosaurus were not a global transfer EADS were not a global phenomenon but the community they lived with are really well studied we've because these are the dinosaurs found in the Western interior a place which is relatively easy to get to which is very dry and so therefore there's not a lot of ground covering - that covers up where the fossils are and because there's been a long history of study that we know these dinosaurs pretty we're familiar to every young person out here horned dinosaurs dome heads duck bills armored dinosaurs Club tailed armor dinosaurs this fauna this community of dinosaurs was essentially limited to Western North America and to Eastern and Central Asia in the Late Cretaceous and just so here are some of T Rex's contemporaries Torosaurus or is it Triceratops I'm not going to deal with that fight um just to say for those of you who aren't up on your dinosaur your dinosaur news there is a question as to whether this represents a second large three-horn dinosaur at the end of the age of dinosaurs or the final adult phase of Triceratops and that hasn't been settled yet and that remains science is about asking questions and we don't always get the answers right away or Club tailed and Kyla Soros here another inhabitant of this community so that's a little intro of Tyrannosaurus but how do we understand how they live we we can't just sit back and film them we can't watch them uh you know behave they're not behaving anymore they just light they're so so we have to use the fossil evidence in order to tell that and really what that is is a bunch of bones so the fossil record shows us the Tyrannosaurus Rex almost definitely had a bunch of bones yes yes it did there are some other types of fossils we can use occasionally we get tracks although there are only a couple prints which are attributable to Tyrannosaurus Rex itself sometimes we have other types of marks in the fossil record called trace fossils so most fossils we think about are the body fossils the things that were once part of the living thing shells teeth leaves bones etc but there's also trace fossils the record of the behavior of animals that's left in the fossil record and sometimes they can help inform us about how these creatures lived and all have a little bit of trace fossil evidence in Taranis or behavior in a bit so I'm going to look at a couple different aspects of Taranis or biology here the main thing I'm going to focus on is feeding in Taranto source because let's face it that's really cool um you know these are some of the largest flesh-eating animals on land in the history of life that's what makes them impressive but I'll also talk about a couple other issues I'll talk about locomotion a little bit and I'll talk about growth in these forms how they grew how to change through time before I got on to the origin question so here's t-rex and the giant Alice or Giganotosaurus to scale with each other so chigga notice Oris is 2 meters so 6 at 6 from the edge of the snout to the back of the jaw joint t-rex a little smaller but not conduct that much smaller and in general you look pretty similar there scary to things but there are details to distinguish the two of them so something that makes t-rex and its relatives different a couple things one they tend to have the nasal bones fuse together these are the bones that run down the top of your face in our case they're relatively short but dinosaurs have very long faces they tend to have long nasals and in Tyrannosaurus they fuse up to a single bone and they do so really early in the history of the group and in the life of any individual and also Tyrannosaurus 10 dev incisors that's weird for reptile most reptiles don't have incisors that is the teeth in the very front of the jaw are normally pretty similar to the ones in the rest of the jaw and in many many dinosaurs there's there's distinction you could recognize what we call the pre maxillary teeth from the maxillary teeth but they're sort of grayed into each other in Tyrannosaurus that's not the case in fact when the first Tyrannosaur pre maxillary teeth were found without skeletons attached they were thought to be evidence of a giant mammal from the end of the age of dinosaurs they looked kind of like mammal incisors but they're not they're dinosaur incisors so here's our view from the underside and their little scrapey teeth um they have serrations on them they have little cutting edges but both serrations both rows of serrations are in the back of the tooth and they're much smaller than the other teeth and trace fossil evidence from bite marks on duck-billed dinosaurs from Asia suggested Tyrannosaurus use those teeth to scrape the meat off sort of delicately off the bone when the so they're either finishing up or maybe trying to get a muscle detached to munch down on it but of course the teeth that interest most people are the rest of the teeth so those are the those are the little incisor like ones here are this giant massive ones and despite almost every popular book and documentary to the contrary they did not have steak knife like teeth because the teeth of tyrannosaurs are almost as thick side to side as they are front to back and that's not the shape of a steak knife it'll be really hard to cut anything with that there are many meat-eaters in fact the ancestral or original condition meat-eating dinosaurs is a steak knife like tooth and in fact if we had a complete one here the crown the part that sticks up above the gumline and the root the stuff that dips down into the socket are about the same length in a typical ordinary meat-eating dinosaur tooth in Tyrannosaurus it's different they're very thick from side to side and the root is twice as long as the crown so they're much more deeply anchored and much thicker from side to side these are not cutting teeth these are pulverized pulverizing crushing piercing teeth at least that's what they look like and so that's one thing we could do we can look at these teeth and begin to infer how they used it from the morphology that is the shape additionally if you look at the inside of the snouts of meat-eating dinosaurs most meat-eating dinosaurs here's a Dallas or called sign Raptor for instance they don't have a solid roof on their mouth so if you stick your tongue at the top of the behind your teeth in your mouth you'll find a layer of bone going across there and because mammals have that that's normal for mammals a crocodile that would do the same thing would feel that a dinosaur typical dinosaur would not just they've like a lizard or a snake they don't have a hard palate in front tyrannosaurs did they did have a hard palate they were more like a crocodile more like a mammal in that context but what does that suggest that does suggest in terms of the biomechanics and some some computer studies have helped support this that Tyrannosaurus could do something most mediating dinosaurs couldn't most meat-eating dinosaurs had jaws or pretty strong when they clamped down on something but not so much when they tried to twist side to side it's not as strong and in fact along the top of the skull they'd have a lot of pressure building up in contrast Tyrannosaurus with that solid palate and remember I mentioned that those fused nasals can actually clamp down and twist and turn or hold on to things which are twisting and turning and not suffer as much stress in the skull they're better able to absorb it so they have better strengthen what we call torsion which is twisting so they seem to a Fed differently and that's consistent with the shape of the teeth instead of being steak knives that just cut and slice through things these Pierce crunch hold and then twist a different mode of feeding that's been called puncture and pull as opposed to the bite and slice of a typical meat-eater so a different approach to taking down its prey items or eating things that they found that we're already dead now related to that if you look at the faces of Tyrannus of Tyrannosaurus and other meat-eating dinosaurs they're different shapes and these aren't distorted these are actually pretty good skulls in both case typical meat-eating dinosaurs have very narrow faces tyrannosaurs have very wide faces rounded snouts big wide backs of their head and I'll come to some of the implication of that in a bit in terms of their senses so from these lines of evidence those of us who work on Tyrannosaur biology have suggested that tyrannosaurs actually fed in a different fashion than the other dinosaurs that they had this puncture and pull method that they use their jaws to both capture the prey and also to take it down but it would be good to have independent evidence and so we look for it and there it is we have cases of the horns of triceratops that have been bitten off and re healed so it was an animal that was alive that at a horn that was bitten off where the puncture marks matched the bite of a Tyrannosaurus we also have the backs of the the rear end of a duck-billed dinosaur that got munched on and REE healed and the shape of the bite matches tyrannosaurus or it would match the bite of a Tyrannosaurus like animal in an environment where the only giant predator known as Tyrannosaurus the simpler explanation is it was Tyrannosaurus and since that bite was revealed that was a living animal and that's an important thing about the question of whether Tyrannosaurus would go after law body pray while they were alive some of my colleagues one of my colleagues thinks that it fed exclusively on carrion on already dead animals and certainly it would have because you know it doesn't fight back but live animals which do fight back seem to have been on the diet and the reason we can tell that is because we have these cases of failed predation and only case is a failed predation where the prey got away are going to be recognizably different than scavenging because when you eat a dead thing or if you kill something and eat it the bite marks are gonna look the same because it was kind of dead and it can't heal but if it something that got away it could heal so you know that was bitten while it was alive but do we really have evidence that this was bite marks from a t-rex does it really going into the belly of the t-rex well the way to find that is to see what comes out of the belly of a t-rex this is a t-rex poop yes we have fossilized poop they're called coprolites which means poop stone really and it's about 2 liters big so think of a two-liter bottle of soda that big and inside of it are the poet I thought I had images that are the partially digested bones of small plant eating dinosaurs that were crushed and pulverized the way the teeth of a Tyrannosaurus could do and no other meat-eater so that's good evidence that Tyrannosaurus would munch down on its prey in ways that bite and slice predators would not of course Tyrannosaurus is famous for one thing that's really small and that's it's dinky little arms that's it that's its arm it cannot its two hands couldn't reach each other it couldn't reach the mouth you know it it couldn't reach lots of things oh that's why they were so angry so you know what do they use them for umm well I think the big solution is they didn't use them very much and that's why they were so small their body didn't put a lot of energy into building them and it's true that the later tyrannosaurs have proportionately smaller arms in fact the Asian cousin of Tyrannosaurus called Tarbosaurus has proportionally even smaller arms and hands than t-rex um so it looks like they were on their way out maybe if the extinction event didn't occur tyrannosaurs that lived in 220 million years 30 million years 40 million years later may have lost their arms altogether but that's you know pure speculation although you know technology could help out so something that has been the research of colleagues of mine primarily out of out of ohio have been looking at can we reconstruct the census of Tyrannosaurus or other fossil animals and in some cases it looks like we can because of attributes with regard to parts of the body that preserve details associated with the sense organs or with the computer that runs the sex sense organs and that's the brain so for example we can look at the placement of the eyes so here's t-rex with eyeballs in place and here's a big Alice or after Camptosaurus it's eyeballs would go there and there and it shows us something t-rex could look right at you and what that means is with both eyes focusing on the same target they've got a lot of depth perception because in order to get depth perception you need light signal coming from two different eyes and then the brain adds it up and tells you how far something is something that get out Acrocanthosaurus or an Allosaurus didn't have as much overlap it had some it had much better vision off to the side much greater peripheral vision but less concentrated depth perception in front in part this may have to do with the type of prey they're going after African thesaurus is a dinosaur that's going after basically big walking walls of meat which are the long necked plant eaters there were as a show there are a few long at plant eaters and Tyrannosaurus world but they were relatively rare whereas in the world at McCann thesaurus there's a lot of these big ones and you don't really have to be that precise to see where they are but Tyrannosaurus is up against armored dinosaurs like ankylosaurus or horned dinosaurs like Triceratops or dinosaurs like the duck bills that have some evidence for complex social behaviors we're getting in really precisely might be really advantageous to get in there get that blow in and take it down something you might not think might be easily preservable but turns out there's some evidence for is the ability to smell so what how well did Tyrannosaurus smell probably stank but yeah okay so uh but the brains of dinosaurs and other meat-eating oso and other other vertebrate animals other animals of the backbones have the same part of the brain in the same spots all across the vertebrate kingdom so we can tell where the parts of the brain associated with smelling are and when the where the parts associated with vision are where the parts associated with balance are and so forth and you can actually use a CT scan on a fossil just like you can on a living human and reconstruct the shape of the brain so there's the brain of t-rex not that much there okay not that much therefore mammals okay for dinosaurs I should point out that's twice as much brain as Carcharodontosaurus has at the same body size some um t-rex has to represent so and we can look at the part of the brain associated with smell and it's been noticed for a long time that is quite large in Tyrannosaurus and so they got a lot of good computing associated with the sense of smell and potentially would have a very good sense of smell now some of my colleagues well one of my colleagues has used that as evidence for Tyrannosaurus being obligate scavengers that the only scavenge because it's true that there are some modern Birds the turkey vulture with this phenomenal sense of smell and yes it would be good to be able to find carrion from a long distance but we also have modern predators with a really good sense of smell I think wolves so just cuz you have a good sense of smell doesn't mean you're a hunter or scavenger it just means you have a good sense of smell so if we plot the relative size of those olfactory bulbs against the body size and we see down this line that's typical meat-eating dinosaurs so those are like the big the big Allosaurus and so forth it's true that Tyrannosaurus have these really disproportionately large smelling parts of the brain as does one other group immediate errs and that's the Raptors so if my colleague was being honest he would use this as evidence that Velociraptor was an obligate scavenger and therefore was incapable of taking down prey I've never heard of actually say that so um despite all these documentaries he's been on about it anyway so um yeah so basically it looks like we have two different groups of meat-eaters that have really really good sense of sensory equipment here now what about the running ability of Tyrannosaurus and other tyrant dinosaurs well they're really big animals they probably as Lisa's adult size didn't spend too much of the time all out running because simply by that sheer mass that would be dangerous if they tripped and fell that's a lot of weight coming down from you know 310 feet up in the air crashing down if that's where the belly is coming crashing out though that's a nasty fall but can we say anything more than that well if you look at the hind limbs the legs of Tyrannosaurus and compare them to other meat-eaters they have a funny looking foot if you compare it to a more typical one less majungasaurus here looking straight on here's a Tarbosaurus of Tyrannosaur and Allosaurus in most meat-eating dinosaurs this middle long bone of the foot is about as wide as the other two from top to bottom that's normal but if you look at the foot bones of Tyrannosaur this middle one is a wedge with a pinched out middle here and it's a lot more proportionately skinnier and longer for the same size and so i and the various other colleagues since have looked at the implication this for one thing we can show that mathematically it really is demonstrable so these red squares or the taranis let's put these guys up here so you know all is milking so there's Tyrannosaurus and these are the ostrich dinosaurs ornithol memo sores if you've ever seen the first Jurassic Park movie that's the flock that goes running over the kids at one point here are the giant Allosaurus and so forth and so most of the big meat-eaters have shorter feet for the same body size then do Tyrannosaurus or these ostrich dinosaurs or most of the other dinosaurs down this line who have the same piston structure in the foot so they have a longer foot a skinnier foot a more interlocked foot for the same body size which are attributes in the modern world we associate with faster moving animals does that mean that t-rex ran as fast as racehorses no probably not it didn't have to though it wasn't chasing racehorses it was chasing duckbills and horn dinosaurs and its foot is a lot longer proportionately than those dinosaurs so all you have to do is be faster than the animals you're trying to get are in your environment you don't have to be faster than hypothetical creatures from 66 million years in the future a one really important line of evidence of the lifestyle of dinosaurs and other fossil animals has come to light in the last few years is our ability to reconstruct how they grew through time and there's a way to do this and it requires samples it requires a number of individuals you can't tell it from just one individual but if we have multiple individuals at different growth stages we can begin to reconstruct the lifecycle of dinosaurs and this is actually a reconstruction of 1 2 3 4 5 different growth stages of Tyrannosaurus Rex to scale with each other and in fact the little guy that won their theory is two-year-olds and also explain in a moment how we know it's 2 years old here's an 11 year old Jane oh that's the name of the individual we don't know if it's female or not that's the big one from Carnegie an older individual well it turns out that dinosaurs like many types of vertebrates actually have tree-ring like growth in their bones they lay down this so-called line of arrested growth about once a year so if you've got a fossil you can slice into some of the bones and count up the growth rings the largest number of rings you have is the minimum age that dinosaur could have been so you've got an age but you also have the dinosaur size if you got enough of the skeleton you know how big it was so if you plot the size of the individual versus the age of the individual you can do a growth curve we can also see when they stopped growing this is a rib of the giant t-rex specimens ooh and it shows that at the at about age 19 after that point those growth rings just stacked right on top of each other we call it the external fundamental system and it means it stopped growing rapidly it reached a basically full size individual at that point so we can map out growth curves of these guys and when it turns out with tyrannosaurs they start out really small so that that's squared that's that two-year-old and then they start to hit a rapid growth phase and tyrannosaurs it seems to be around 11 or 12 goes up for a while Peters out around age 19 or 20 and then they have there they reach full size at about 20 and if we ignore the body mass that could be a human growth curve little baby growing up as a kid sort of a stable growth rapid growth around age 11 or 12 petering out about 11 or 19 and then you know little growth afterwards but not much in terms of adding a length so we now can look at the growth cycles of dinosaurs which is something we couldn't do before now one last major fields of research that I've been involved with here and that is reconstructing where Tyrannosaurus and its kin came from because for a long time our fossil record was a lot more spotty than it is now that means we didn't have as many time lay and spots around the world so we didn't have as many dots to connect up and so prior to the 1980s there were sort of two different arguments of where tyrannosaurs came from there's Tyrannosaurus there's Gorgosaurus it's earlier lighter built cousin one idea is that it was a supercar Nisour as I used to call this idea that is it was the last in a line of meat-eaters that included the Allosaurus and so it they inherited giant-sized from giant-sized ancestors however as early as the 1920s people had noticed some attributes some skeletal features of Tyrannosaurus that were more like the little bitty dinosaurs and actually this guy up here is projected larger these are both projected larger than life-size that's pretty close to the life-size is projected here that there were features of the skeleton of Tyrannosaurus that were more like these little guys then we're like these giants and so maybe the little Raptor dinosaurs were where the Tyrannosaurus came from well that was a question because we didn't really have a method to choose and sort out between that that changed in the 1980s and 90s when a new type of technique for sorting out evolutionary relationships was developed and this technique which looks at the the pattern of observations of transformations of evolution and sorts out the simplest explanation for any set of data started to recover the fact that tyrannosaurs were in fact descendants of small bodied meat-eaters and not descendants of giant meat-eaters that there were little little birdie dinosaurs grown huge so tyrannosaurs are part of this larger group called the Celera soars that included some of those little guys I showed before but also this group the Raptor dinosaurs the ostrich dinosaurs and the birds because one of the other things that came out of these studies is that birds are not relatives of the dinosaurs they are a type of dinosaur in fact they are a type of many wrapped or reformed Solaris or dinosaur and the Tyrannosaurus were actually pretty close to birds they were really super close to birds but they were closer to birds than they were to Allosaurus or Megalosaurus or so forth but still all that was based where we had the tyrannosaurids the Late Cretaceous and then not much beforehand and in the last decade and a half dad has changed these are all the new Tyrannosaurus that have been named in the 21st century um that's a lot of them and some of these many of these are really complete skeletons a couple of these are actually within Tyrannosaur today itself among the Giants but a lot of these aren't and additionally with the information from these skeletons we were able were able to see that some previously named dinosaur some named as early as the 1860s were actually also tyrannosaurids member the larger group and there's a handful that maybe they are maybe they are it's hard to say so our understanding of Tyrannosaur evolution has greatly increased and one of the things that we've discovered is that they greatly increased that they really really dramatically rose in size because most of those tyrannosaurids are small dinosaurs or medium sized dinosaurs so we filled in a gap not only of time but also of size running from little bitty ones to medium-sized ones to larger ones on up to the great giants of the Late Cretaceous and they also tell us something about the transformations that they went through for example here's an early Tyrannosaur called guanlong the crested the crowned dragon it's got long arms it's got three fingers with great big claws they still had really long grasping arms like most meat-eaters but it had those fused nasals and it had those premaxillary teeth that look like incisors that showed its taranis all right so that that was one of the skeletons here's a drawing of the more complete one of guanlong and there's a restoration of what it looks like long armed fast running medium-sized predator or little D long D long is a little guy probably not much more than six feet long as an adult there's its skull it's got those little u-shaped incisor teeth it's got it's fused nasals and it's got feathers or at least has got fuzz it's got little fuzzy projections coming off the body which we had already discovered among some of the other meat-eating dinosaurs from China from the same rocks that it was found in and we were beginning to guess that because other Celera sores had this fuzz that Tyrannosaurus might as well but D long was the first one to show it but with those discoveries that okay maybe D long a little bitty guy a 6-footer had fuzz on its body but surely a giant Tyrannosaur wouldn't because it and that's a lot dis logic behind that after all if you think about it look at an African elephant or an Indian elephant they're mostly hairless even though we know they come from furry animals and most of their smaller relatives are very furry so maybe t-rex and other giant Tyrannosaurus would have been not so much fuzzy well that's a reconstruction of D long last year this guy came to light you Tyrannis known from three nearly complete skeletons preserved in the same type of lake deposits that preserve the sort of filaments and there are two of the good skeletons that actually overlap and it was covered with fuzz a 1.4 ton giant with fuzz on the body about eight inches long that look for all the world like the little little fuzzy feathers coming off of emus and cassowaries so now we can't say that the giant tyrannosaurs were necessarily just scaly that at least some of them were fuzzy now at present we have never found t-rex in an environment that would preserve the body covering to any great degree they haven't found him in Lake deposits so we cannot yet reject the idea that they were fuzzy because if we see this is the distribution on the family tree of this filament or fuzzyness true feathers so far are listed are limited to this one group that is with a branch and branches coming off of that and branches coming off of that but all these other ones have fuzz and so our simplest explanation is that fuzz evolved in their common ancestor and that Tyrannosaur is like t-rex were fuzzy animals so weird as it is we may have to start getting used to this image of t-rex you know a lot of us are more comfortable now maybe juveniles like this you know there's a representation of the two-year-old being fuzzy but you know maybe even the adults kept it on part of the body and you know pure speculation and literally arm waving here maybe that's what those little tiny arms were still for maybe they were still signaling with them just the way some flightless birds can signal with their otherwise useless wings again pure speculation until we find the impression of that we don't know they had feathers on their arms well there's a lot of things we want to know about tyrannosaurs you know what were their their social behaviors like what were what was their their the other aspects of their biology we think of Tyrannosaurus as being very spectacular because it was the last and greatest of the Tyrannosaurus but that's really by accident you know it wasn't doomed it wasn't destined to be the largest and the last they could have gone on beyond who knows what would have happened t-rex was unlucky enough like this individual to live at a time when giant rocks fall out of the sky and brought the world of the Tyrannosaurus to an end so t-rex was the very last of the giant Tyrannosaurus and it lived they lived to see the day when the great catice Cataclysm end of the age of the giant dinosaurs and allowed the fuzzballs the mammals who have been with the dinosaurs since the very beginning to take over the earth so I just wanted to end there with and the end of the Tyrannosaurus with a very brief overview of the life of these creatures there's still plenty of more to discover about them and I don't even know what questions to ask and that's the important thing is that people are discovering new techniques all the time and new approaches to ask questions that we can get information out of the fossil record to bring these wonderful creatures to life so thank you next question is from Jake from Redmond Washington he said how fast can the average Tyrannosaurus go he wants them in miles per hour laughter hour right now it's easy to answer at zero but back then that's a really good question and I wish I could answer you but I can't and here to turn the question around how fast is any given animal today and we don't know and when you watch a TV show or you look at a book about animals really we know the actual top speeds of just a handful of animals that we can run under a controlled condition to see how fast they are most wild animals we don't not able to do that we can't train them and honest-to-goodness this is the way how they Strack how fast wild animals are going to get in the Range Rover they're in the Serengeti so because we don't know how fast modern animals are for the most part it becomes that much more difficult to try to reconstruct how fast an animal who lived in conditions different than us different levels of oxygen in the environment that might be different power to the muscles muscles arranged in fashions different than any living animal I'm the same basic patterns but different sizes too many question marks in there to get a real good number I'd love to know what it is though okay next question is from Virginia she's a student here at the University of Washington I've always wondered with dinosaurs being so big how would they manage to reproduce without crushing each other ah I guess the answer was very carefully but obviously they did it uh if some people have suggested maybe some of them went into the water to do it maybe I don't know but it's all we're in really dry environments so at the ones that make me wonder are some of the spikes back guys I don't oh so I got a follow-up question here from Jacob from Port Angeles Washington he was wondering do you think t-rex of brood its eggs ah yeah that's a that's a great question we know that some of the the group that I called mani wrapped or reformed ease the ostrich dinosaurs the Oviraptors the Raptor dinosaurs did brood their nest that we we have the the nests and the skeletons to show that we even have nests of Tyrannosaurus sized Oviraptors that brooded their nests and now we have kind of good evidence that taranis so even big Tyrannosaurus were fuzzy and one of the aspects of fuzziness could be for brooding we don't yet have a Tyrannosaur it nest or trance or nests and I'd love to see what they look like if you a little further down the tree that is the evolutionary family tree we start running into meat-eaters that don't have a big space in the middle of their nest for the parent to sit down in and those ones probably didn't brood it directly they were probably more like alligators and crocodiles and a couple group of primitive birds that sort of cover it with vegetation or arranged vegetation around it but for tyrannosaurus themself we don't know it's a really good question next question from Tony's from Tukwila did Tyrannosaurus have rocks or gizzards to help digest food you know we have yet to find gizzard stones or gastroliths is a technical name in tyrannosaurids they are known in some other members of the theropod uh the meat-eating dinosaurs including some which were meat eaters and sometimes people think that gizzard stones are just for plant eaters and many plant eaters do use them but there's a meat eater from from Portugal called Lauren yeah Soros and it had gizzard stones in its belly so it's not it's not unthinkable that Tyrannosaurus would have them but we have a fair number of pretty complete skeletons that were found out in the field and to my knowledge no one's ever reported them in there Marcus from Bellingham wants to know how wide a t-rex could open his mouth right yeah we get we go look at the jaw joint and they can open it pretty deep they probably had to to get around the legs of animals to sort of get a big bite off of or a question from Rick from Redmond what major should an undergraduate study if they want to become a paleontologist ah there's sort of two two big approaches to doing paleontology because paleontology really is the overlap of two fields it's you've got you either have to be a biologist who knows a heck of a lot of geology or a geologist who knows a heck of a lot of biology and depending upon what university you go to you might be a place where like for example at my university all the vertebrate paleontologists are in the department of geology so that's where you'd want to go and as an when I was an undergraduate that's what I that's what I did because all the I even took human anatomy at Hopkins in the Department of Earth and Planetary Sciences because he didn't teach it in biology because that involved things bigger than a cell at some universities it's all over in the biology department and that's where all the whole organismal biologists are and the geologists are just geophysicist and so forth and at some universities you've got them in both departments and that's great because then you know who knows you can even double major I don't check with your advisors to see if that's appropriate so Nina from Seattle has a seems like a little bit more technical question for you okay is there any evidence supporting nano tyrannous as either a young Tyrannosaurus or its own species right that's it that is that is a big question in the tiny little field of Tyrannosaur studies so there's a skeleton let's see I'll try to back up to it while I'm doing this a skeleton that's called Jane another one that's a skull called Nanotyrannus where there's a question as to whether there we go there's Jane whether this is a distinct separate type of taranis or or whether it is the growth stage age the teenager of the early teenager of Tyrannosaurus Rex now I think the conclusive evidence to reject the idea that it is a juvenile Tyrannosaurus is either the discovery of a juvenile Tyrannosaurus of exactly the same growth stage that has more features with Tyrannosaurus Rex than this skeleton does or an adult of this animal which is clearly not Tyrannosaurus Rex but so far every nano tyrannous found is a juvenile at a stage we do not have we otherwise don't have juvenile T Rex's so I think until one of those other things are discovered the simplest explanation is this is a young t-rex at Nanotyrannus is just a growth stage of Tyrannosaurus happy to be wrong but because that means there's one more Tyrannosaurus PCs but but we need that evidence in order to say it's a distinct form great Lena from Seattle wants to know if t-rex had fuzz would it be wiry or soft whoo that's a good question and I don't know that we've got really a good way of answering that at the moment now from what we see of these long filaments coming off of them they're sort of like down but the problem is no living bird still has that really ancestral proto bird structure all living birds are descendants of animals that have as their basic adult plumage a single shaft with branches coming off and branches coming off that and down is sort of like a degeneration of that kind of but not exactly developmental biology you gotta love it so we don't have anything today that produces so far as I know that produces filaments that are exactly like these things we see on you tirana sandy long and so forth my expectation would be kind of soft but but it's hard to say we could be wrong Deborah from Bellevue wants to know what are your general thoughts on whether t-rex was or wasn't warm blood yeah um I think I think we can reject for a number of lines of evidence the idea that any dinosaur was cold-blooded in the sense of any modern cold-blooded reptile there's too many attributes of them their rapid super rapid growth rate uh there there's some biomechanical evidence that in order to move a body of this size you have to have a warm-blooded metabolism given the amount of muscles they have in them and the fact they're way up above the ground and so forth that they can't they almost certainly weren't cold blooded in the sense of they're contemporary lizards and snakes and turtles and so forth a complicating factor in this whole warm-bloodedness cold-bloodedness debate is that part of metabolism is what's going on inside your body and part of what your metabolism is is what you're taking it from the outside and the outside world was different back then including the relative amount of co2 the relative amount of oxygen that may have affected the relative amount of productivity of plants at the base of the food chain it may have affected the rates of production of heat in the body it may have been easier to have been warm-blooded in the age of dinosaurs than it is now I would say with all that arm-waving going on there the effective end product is they would have been as active as a mammal today how they got to that activity level is yet another and really complicated question but I think in terms of the way it's expressed would be rather continuous activity expressed pretty much the way it would look like if you were at the big cat house or the the big elephant house whatever at a zoo and not what you would see in the reptile house okay I'm going to ask two more questions okay so the same question from a couple of different people Christopher from Tacoma and Noah from Seattle basically want to know how long did t-rex live how what was the lifespan of a t-rex right at present that t-rex called the one that's at the the Field Museum in Chicago is the one that they've counted the most rings on and she was between 28 years old and 29 years old when she died there is another one that's called Scottie that they haven't finished it's a little more obscure it looks like it may have been in its early 30s when it died but we don't see him older than that it looks like dinosaurs lived fast and died young that they didn't have to have really long life so they didn't have a really long life span and there's probably a reason for that and that is up is to turn the question around is is you know why don't ma'am why do I do big mammals live so long big mammals like elephants and rhinos live so long because it takes him a long time to reproduce offspring that the gestation period in a big mammal well in mammals it scales against body size so that a horse takes what nine months were so a rhino a year an elephant two years and indricotherium it'll of the Cenozoic might have been three years and you get one baby after that and that means you need to live a long time in order to have a lot of enough offspring that you gotta next generation dinosaurs are popping out eggs like nobody's business so you know a couple dozen every year you don't need to ever you don't need to have selection for a really really long lifespan in order to be able to reproduce so there's no reason to keep hanging around yep lots of babies you're dead next generation lots of babies so they didn't need to live a long time okay last questions from Alex from Redmond he wants to know where's the best place to find a t-rex ah yeah best places to find t-rex's would be places like Wyoming and Montana and Colorado and South Dakota those four states have produced the vast majority of t-rex specimens there have been some that have been found up in the provinces of Alberta and Saskatchewan there's been some found in Denver there's limited remains south southwest of that but the best place the place where the vast majority of a found are Montana and Wyoming and South Dakota and and a little bit more indeed Colorado you you

Channel: Burke Museum

Views: 155,283

Rating: 4.8804059 out of 5

Keywords: dinosaur, T. rex, tyrannosaurus rex, paleontology, carnivore, predator, Dr. Thomas Holtz

Id: sqkqkxYGNZc

Length: 58min 10sec (3490 seconds)

Published: Tue Mar 19 2013

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Recent discoveries reveal new clues about the evolution of T. rex from a small fuzzy carnivore to one of the largest predators ever to walk the Earth. Studies of the tyrant king's eyes, nose, brain, claws, jaws, teeth, and legs create a clearer picture of how T. rex lived, fed, and fought. We can now map changes in growth and behavior that Tyrannosaurus went through from birth to death.

Dr. Thomas Holtz is a dinosaur paleontologist specializing in the origin, evolution, and adaptations of carnivorous dinosaurs. In this talk he will show us how recent studies of T. rex as well as other dinosaurs, animals and plants that shared his world, reveal how the last of the giant dinosaur predators ruled North America at the end of the Age of Dinosaurs.