howdy so let's get into the more derived Titanosaurus so this is the last sort of group of the sore pods we're going to cover so we covered the earlier macronarians and titanosaura forms brachiosaurs Etc the derived Titanosaurus though are made up of well the taxonomy is actually kind of weird um one particular idea um and we're not really too sure whether to go with it or not one is the lithostrota and the other is the I think it's the Colossal Soria we have an idea that there's two groups of sauropods but what the actual membership of those groups are and what their names are is kind of up in the air okay that's just two ideas that's just you know one idea what we do know is that the titanosaurs are definitely a group and the big thing is that they've done they have a lot of adaptations they actually separate them out easily from the other sauropods one is remember how I said that oh yeah the the neosauropods they've lost all but one toe well guess what the titanosaurs do they lose that one toe another thing that's the titanosaurs do is um imagine that you are standing behind a sauropod and you are staring at that sauropod's hips well most sauropods would have actually kind of stood together in fact we can see this if you go to trackways for sauropods you know you would have seen them walking like this although they're trackways because they wouldn't just be walking with one set of feet would actually look kind of like this that's because they their their back leg sort of steps into the footprint of the front leg and so you'd often see them kind of the trapway is looking like that well there are trackways particularly here in Texas actually that look like this and that's because if you were standing behind a titanosaur and you were staring at its hips what you'd see is this their their hips were extra flared and their legs were modified so that they stood really broadly again further adaptations to allow for an even bigger gut than previous sauropods um so we call this actually the wide gauge trackways so you can actually differentiate between titanosaur and non-titanosaur trackways based upon this adaptation of being wide gauged um you can also supposedly differentiate based upon whether or not they show whether they have the angle claw or not but that's actually really hard to distinguish in trackways in general um you know they're not they're not trying to indicate whether they're a titanosaur or Not by whether they've got that front claw but now they've lost so they've now lost all the fingers they've developed these extra wide hips for their bigger more bulging bellies and they've got something really interesting going on they've got their tails which are kind of generally sort of shortened so they're Tails right well their tails are made of vertebrae at an unusual sauropod it would look kind of like this right so the the sides of the vertebrae would come up against each other with flat edges and there'd be a disc of cartilage in between like that right titanosaurs do it a little differently what do titanosaurs do titanosaurs they modify the edge of the vertebrae so that it's concave on one side and outwardly concave on the next vertebrae and outwardly concave inwardly concave Etc so there would be a a more of a crescent of cartilage here between them and so these ball joints would allow for really a completely different range of motion in their tails and again it's not entirely clear why that would be one theory is that maybe titanosaurs with their extra wide stance and their tails which are shorter and have these sort of ball joints in them that allow us for each vertebrae to sort of flex in different directions relative to each other is that maybe the titanosaurs are adapted for moving back leaning back onto their hind legs and standing up bipedally we've act now I didn't talk about this with the diplodocets but with the deposits there is a rather good argument that there seems to be sort of an extra joint in the tail that allows for deposites with their long tails to lean back and for their their tail to basically be the third leg of a tripod that allows them to reach up it doesn't exactly there's a few conflicts with that because the Protestants the head was also held sort of horizontally and so it maybe wouldn't have given them as much height as we think it would but with the Titanosaurus they seem to have a number of adaptations that seems to be for allowing them to um uh be momentarily bipedal and reach up by lean back and their tails serving as this third leg um the other thing the titanosaurs develop let me just draw a very generic titanosaur here um most titanosaurs have actually their limbs and are actually equal proportion but there are some that are more High shoulder a number of them that we actually find that they're associated with with these little clumps of fossilized bone and after a while of looking at these uh paleontologists figured out that these little clumps of bone were actually little armored scoots that had ossified that had developed bone and they would have sat in their skin like this all right now here's the thing all right um bone and skeletons are sort of an accidental invention okay the only reason mollusks or any invertebrate ever figured out how to make calcium carbonate is because they needed to get calcium carbonate they need to get the calcium in the water it was too much calcium in the water so they needed to figure out a way of getting it away from them because it was hard to biologically do the things they needed to do for their metabolism so early mollusks early invertebrates figured out uh stuff that they could secrete that would make calcium carbonate later on that got retrofitted and made into a way of making shells of making coral reefs of making all sorts of things that invertebrates do with calcium carbonate it's the same way with vertebrate bone um bone originally was sort of invented as sort of a way of maybe making sort of a sharp scale or of of maybe getting rid of a material you didn't like me there was too much um uh too much of a particular mineral like calcium again in the water calcium is a component of Bones and so bone can actually develop wherever your body wants to make bone bone often develops in places where we don't expect bone to occur so as you've probably seen already one thing that's very common is to see the tendons which are muscles actually get ossified bone starts to develop in those muscles in fact in the sauropods one thing that we see is that with the vertebrae in the neck many of them have these long um sideways spikes coming off of them that we call cervical ribs what are cervical ribs those are actually ossified tendons tendons that were that for whatever reason the body felt and it was necessary to start building bone around those tendons um perhaps representing that the the dinosaur felt that like that needed to be that was a place where a lot of stress was being experienced and so bone was needed to reinforce it um it's hard to say either way saltasaurs start developing bone not just on tendons but also in clumps in their skin so was that intentional was that meant to be a defensive measure maybe it's it's a way of basically having armor right you've got clumps of bone all over your skin that looks like armor right um or is it maybe just a way of getting rid of an excess mineral that's in your environment that doesn't happen so often on land that's a thing really we gender that that happens a lot in the water in in the ocean but maybe online maybe it could maybe maybe they were living in environments where they there was stuff that they needed to get rid of I don't know like maybe like salty fresh water or something like that um a lot of these were certainly living around very shallow seas because many of the continents were covered in Shallow salty Seas at the time so maybe there is something associated with that it's hard to say it's really hard to say all right so um but but what we do now is that these osteaderms exist and in fact we found that they are common across all of the titanosaurs which is a bit of a problem with the classification that I gave here is that the kind of titanos or yeah that this group here lithostrota that means um bony scales or uh bony uh skin so that group originally was defined based upon those are the titanosaurs that develop armor in their skin well it turns out actually it's all the titanosaurs can do it and it's really random where there's really close relatives of of titanosaurs more from one titanosaur to another and one one is often found with that serums and the other isn't so why is it so evolutionarily noisy we don't know but it's spread all over all over the Titanosaurus so they've developed these extra wide hips they develop extra osteoderms in their backs they've got these um round surfaces between vertebrae in their in their tails these are what we call actually sacral sacral vertebrae so there's different names for all different vertebrae in a dinosaur sacral vertebrae are the vertebrae in there um in their tails so and then there's this other group here so this colossosaurus so lithostrota those are kind of um smaller uh small they're generally smaller they're generally the smaller titanosaurs one that's really well known the basically the most classic of Titanosaurus is saltasaurus and it's one of its really close relatives is um Alamo source which I mentioned before is a very common not not our state fossil but it's a very common Texas uh uh titanosaur and in fact Alamosaurus is really interesting because it becomes really common across North America in the late Cretaceous basically sauropods work found in the Cretaceous and then right at the very end Alamosaurus gets everywhere so it's not that sauropods were successful in the Cretaceous it's that sauropods hadn't gone in they somehow went extinct in North America and then they were being kept out as they were doing their own thing in South America and in Asia and then the uh some land bridges get formed right at the end of the Cretaceous they get back into the North America and they get everywhere again and so Elementor shows that they actually can be quite successful in the Cretaceous so um I remember when I was a kid I'd see like pictures of like a sauropod and a T-Rex and like it'd be like what is wrong with this picture well sauropods and T-rexes weren't really like in the same environment together no we now know that T-Rex and Allosaurus was actually um in the same environment also element of source we did we've known about it for a while so it's been known since 1926. and those social sources will look like this as sort of a stubby looking uh titanosaur with osteaderms in its skin well we actually now know that allenosaurus can be enormous um we used to think element Source was only a small sauropod it turns out that that belief was wrong um and uh like I said it's a name for the Ojo Alamo formation um not the Alamo but it is a classic Texas dinosaur in fact if you want to see a really great Alamosaurus go to the um the Ross Pro Museum in Dallas and they have a really great allenosaurus reconstruction there Okay so we've got allenosaurus it's in the North American the likert Cretaceous okay that's all great well what's this other group what's going on with colossal Soria that sounds cool they're colossal lizards what's why is why are they named that well that's one thing there's also another uh name they're called something like longasoria but what is going on in this particular group is that that is where some that is where the biggest sauropods that ever lived seem to come from is this other group that we don't really have a very good definition for two particular sauropods that you should know about in the colossusauria um one is Argentinosaurus and we've actually known about Argentinosaurus for a while uh it was named back in the 80s but as we've um consistently looked more at it we really think that that is the biggest sauropod we found so far and it really truly gigantic but a close close relative to it is a sauropod named so Titan and we know that one much better so Argentinosaurus is really fragmentary Titan actually we found six potato Titans all together in one deposit in Argentina this was reported in 2017 and that's in fact why you can now go to the amnh in New York City or you can go to the field museum in Chicago and you can see an enormous cast of potato Titan because when we've got six different individuals we have enough information that we can kind of piece together a lot of what would it looked like now here's the thing I said this before no heads no heads to these things and this is very common there are no skulls found in fact often this is the thing that happens with sauropods you don't yet be in detail you don't get into Limbs and you don't get the head so why is that well what happens is that when you've got a big sauropod that is dyed it takes a long time for it to get buried right so even when you've got six sinking potato Titans some of the biggest vertebrates that ever lived laying on land that's basically six mountains of rotting meat and so predators and scavengers are going to come by and they're going to pull off whatever they can pull off and that means that the head and the ends of the legs and the end of the tails are going to be the easiest things to pull off and then eventually it's going to get buried and often what we find from sauropods the most common thing to find are basically ancient uh bone logs they're they're they're vertebrae either from the tail or from the neck or from the thorax found still right articulated with each other as they would have been in life because of course there's not much in that that anything would want to eat once you've pulled away all the muscle and stuff and so um those are the things that we often find from a lot of especially these biggest sauropods however with Attack on Titan we have six individuals all headless but that's enough to piece together a lot of the skeleton actually and they're in different different stages of like some number juveniles and some of them are adults and then we can take what we know from other titanosaurs and we can say what say the head of potato Titan would have looked like and then we can use that to then say wow attack didn't look like this and so go to the field museum go to the m h go to the Roswell Museum see the amazing titanosaurs that once lived in North and South America um uh so uh in terms of really what unites this group by the way the Colossal story out or the longest Soria it's uh let's not even go there it's it's actually really difficult to talk about any particular character that unites that group which probably should suggest to you they're probably not a very good group in terms of of evidence that the evidence for that group existing probably not very good this is probably a big area where all the relationships among these things could change at any moment in time because we could find more evidence that changes everything so but this is where we set in terms of around the time when potato Titan was described in 2017. so um this is the Titanosaurus they were wonderfully successful in South America throughout the Cretaceous they were wonderfully successful in North America once they got back into North America and um overall they were a really exceptional group they were again the even within a world now dominated by angiosperms which are much more nutritious plants they were developing further that sauropod body plan of being enormous long necked and having an enormous and being enormous for the sake of that enormous belly why I mean like were there trees really as tall as required in Argentinosaurus to to sit back on its own hind legs like are we talking like there were trees that were regularly 200 feet tall in the Cretaceous I don't know I mean maybe there were but we haven't found evidence of that um why why why do they need to get so big what was going on at the time that that you would want to be so enormous I mean one thing to think about is that size is itself a defensive mechanism predators don't go after things that are too big for them they're too scary for them all right so maybe the titanosaurs were often evolving to these really big sizes and by the way it's big size just like how osteoderms really aren't just held among lithosturtia big the big titanosaurs aren't just in colossal sorry Allosaurus is really quite big why is it the big body size was evolving over and over again well maybe it could just be that you know in general if you got to a big body size that was a good way of of escaping predation it how overall our study of sauropod Bones suggests they didn't grow very fast though they it basically took 20 or 40 years to become as big as they are and that's a lot longer than it takes say an elephant to become as big as an elephant does um frankly our way of growing where we take like 20 years to grow that is ridiculously long for any sort of mammal mammals grow really really fast sauropods they took a long time and that means that actually little sauropods were probably doing little sauropods which one should have been more numerous than big sauropods the little sauropods the ones that just hatched and were probably not taken care of or watched over by their parents at all we're probably doing something very different what the big sauropods were doing and in fact we found evidence of this there's been recent um uh discoveries of juvenile Diplodocus and they have a completely different tooth type than what adult Diplodocus has which suggests that they have a different diet um so overall but and yet at the same time small story pods usually we don't get to see those um uh saltasaurus actually is one of the few sauropods that we've ever actually found um eggs from we actually have nests of salsasaur eggs they're very round I recall correctly round eggs um uh so um you know what were the actual drivers of a lot of this in in sauropods overall in titanosaur specifically there's a lot of questions here and frankly I expect that this is probably going to be one of the things you're going to see a lot more about in the next you know 10 20 years in dinosaur Sciences a lot a lot of what I'm I just told you in this chunk it's probably probably going to be changed a lot in the next decade or so