So this is the final lecture, a chance to wrap the course up, as we run through the final 250 million years of evolution. In reality, we're only going to get to about 180 million of that, but that's still a lot to cover in a one-hour lecture. So a reminder of where we left off last class. So here is the reason why the Joggins fossil cliffs are so important is because we've got these two big lineages here of the amniotes. These are the vertebrates who laid shells with eggs with shells on them. These two big branches, we've got this one over here, which leads up to crocodiles, birds, and dinosaurs. And we're going to refer to these as the diapsids, and these are all diapsids, but there were other branches that came off here. So sometimes you see the term soropsid, and that's actually one you'll see in one of the videos. I'm going to link you guys to earlier on or later on, but just to keep things simple, we're going to call this whole group here the diapsids, even though it's not technically correct, because it's going to include these ones here as well. The other big lineage that comes off here, these things are the synapsids, and they lead ultimately to us, to whales, to all of the mammals are up in this. So that's just a reminder of where we got up to last class.  The story we're going to go through today was this. One big group dominating, then a mass extinction, then positions change. You guys know this story, right? The reptiles dominating the world, an age of reptiles, and then them dying out, and mammals ruling the world. That's not incorrect, but it turns out not to be the story that we're going to tell right now. So the story we're going to tell right now is actually about synapsids. So let's jump back to Prince Edward Island. Remember in Prince Edward Island we had this beast here, Dimetrodon, and I told you that Dimetrodon shows up in every child's dinosaur play kit. It's seriously in every single kit. I told you, paleontologists love that because Dimetrodon is a really wicked beast, and I also told you they really get irritated by it. Why do they get irritated by it? Because Dimetrodon is not a dinosaur. If you click this link, it will take you to an article literally called Dimetrodon is not a dinosaur. It's a really interesting article. So why is Dimetrodon not a dinosaur? Well, if you look at the skeletal anatomy of this, there's a whole bunch of features, but in particular, this white here, this hole, the fact that it has one hole here, rather than two, these are called temporal finestre, that's a finestra singular, finestre plural. That means that this is a synapsid. So all of our lineage, our branch of the amniotes, had one hole here originally. Ours has been kind of covered up by additional bony processes, but you can still see where it used to be in even the human skull. The other thing is the teeth here. This diversity of teeth is a classic synapsid feature. I wanted to show you guys a quick little video, but it might get cut out for, might get flagged for copyright reasons. PBS gave me permission to put it in, but they also said YouTube's algorithm might cut it out. So instead, I'm just going to put this up here for you. If you Google this, you can choose to watch this video if you want. It's about five minutes long. So I hope you will agree that Dimetrodon was a pretty cool beast. This is Adaphosaurus. Often you see in the videos Dimetrodon fighting Adaphosaurus. Adaphosaurus is a Dimetrodon-like organism except it's an herbivore. See that big belly here for digesting, digesting vegetal matter and the comically small head.  So this is Adaphosaurus. It's a herbivorous form. And these things were the main, kind of the largest land animals that existed in the early part of the Permian. So the Permian really starts off as an age of synapsids. And it continues as an age of synapsids. You're going to see in a second. But it wasn't just about synapsids. There was a ton of diversification that happened within the various lineages of the vertebrates, of the terrestrial vertebrates. The amphibians got really big and scary. This is a thing called aereops up here. This is a 200 pound plus beast. Here's it's skeleton. If you look at these teeth over here, I mean, this thing is the size of a large man. I mean, this is a terrifying animal. It could take you down. I don't know if it would, but I mean it could if it wanted to. This is a, you know, a salamander, I put quotation marks around this. Timmy spondyls are the group. These things showed up in the carboniferous and they stayed around all the ways pretty much till the end of the Mesozoic, although they had their heyday kind of back here. Here's another beast here. This is Diplocolis. This is a weird boomerang shaped amphibian. As an interesting side note here, recent discovery in Texas, a whole series of these Diplocolis specimens with their noses bit off or their faces chomped on in various ways. It was linked to Dimetrodon here. So we think that Dimetrodon was actively feeding on these amphibians right here. They were living side by side in the Permian, being really weird. I mean, everything is being pretty weird. But note at this point that we don't have any of the traditional stuff. And also that you have probably never heard of any of these amazing beasts. We have these amazing organisms. The life of the Permian gets completely overlooked when we do the history of life. We just jump straight from the Cambrian most of the time to the age of the dinosaurs. Here's a thing called Mesosaurus. So this is a reptile that we actually talked about earlier on in class. This is an aquatic thing that lived in South Africa and what is now South Africa and South America. And it was actually one of the fossil lines of evidence that the earliest thinkers in kind of plate tectonic theory used to point out that the distribution of the continents today had to have been different in the past. So we talked about this guy in class. I was pointing him out here. This is a primitive group of reptiles, the Mesosauridae. And if you want to read more about the kind of technical position of this thing within the Seropsid, you can click on this link right here. It'll take you to a phylogeny that you can take a look at. All right, so that's where we are in the kind of beginning of the Permian. As the Permian continues going on, it really does just become the age of the synapses. And we get this group here of really advanced synapses that start evolving. And they evolve in concert with environmental change. So we've got Pangea forming in the latest part of the Carboniferous, kind of earliest Permian.  And if you remember when we were talking about in class, we were talking about climate, you remember that the interior of large continents tends to be really dry because clouds form here and they rain out before they get there. You also remember that on one side or the other of mountains, you tend to get really large shadow deserts as well. So what we end up with here is a large dry interior of this entire super continent. The other thing we talked about in class is remember that when you've got, I think actually it was 1107 that we talked about this or you guys took 1107 with me, where you've got large interiors, what you tend to get is these very extreme seasons. And you'll see this in the summer of Ontario versus the summer in Nova Scotia because the water, a body of water takes a lot longer to heat up. And so it kind of acts as a moderating influence anywhere along the coast. Whereas if you're in the interior, you heat and cool really rapidly with the seasons, which is why Ontario has really cold winters anywhere away from the Great Lakes and really hot, humid summers. So we would have seen not only general dryness here, but fairly extreme temperature contrast in large parts of the interior of this giant super continent of Panchia. So this is not a particularly nice place to live and we can see evidence of it if you go to PEI or you go to the Magdalene Islands and you can see these deposits here. Remember that redness kind of represents an arid, deserty environment, but you also have evidence of fluid flow. So this is a monsoonal climate, one where you get wet intervals punctuated by really dry intervals. And within them, these group here, these advanced synapses that we call the therapsids, these things thrive and they take over and they form a completely fleshed out ecosystem that is pretty much equivalent to what you would see if you went to Africa today. You can find organisms that are analogs in terms of size and behaviors to pretty much everything you're gonna find in Africa with the modern mammals, except that we are back in time, roughly at 250 million years ago. So these things had parental care, they had hair, they formed large herds, things like water buffalo would do today or elk or caribou would do, diverse communities with super predators in it, large armored herbivores, all of these kinds of things, these are reconstructions of some of these therapsids here. So a savanna-like ecosystem that formed, except this is forming, in this case, millions and millions of years before we get the dinosaurs and several hundred million years before we really get large mammals showing up. These are not technically mammals, but these are our lineage, right? These are synapses, these are our lineage. So I invite you guys to go check this out, the BBC series, you may have seen Walking with Dinosaurs, they made another one called Walking with Monsters, and it has some great scenes with reconstructions, a little bit out of date now, but still really good. It's from 2005 of both the early synapses, like Dimetrodon as well as the later Therapsids. You can also check out this video on PBS Eons as linked here in the PowerPoint. You can also see the link right there or just Google this, and it's got a really good overview of the synapses, particularly the therapsids. So here are some of the therapsids just to show you what these things were like. So this thing here is 10 foot long. I mean, this is maybe the equivalent of something like a water buffalo. This is a massive, a massive animal. Here's a thing called a disinodont. This thing is about the size of an elephant, and it would have played kind of a similar role. They form huge herds, just like elephants form large herds. Within the carnivore role, we had the terrifying Gorgonopsids. These are a group that really do not get, do not get just as applied to them. So this thing here, if you look at this, the saber tooth-like monster here, you could think this is an actual lion or a tiger. It's about the same size, except this is one of these therapsids. Here is another one here, another one of these Gorgonopsids. This one here weighed about 700 pounds, we think. So it was roughly the size of a grizzly bear. And a similar kind of morphology actually as well, a reasonable analog to something like a grizzly bear. So these are all the advanced therapsids. The advanced synapsids, rather, they're called therapsids. So these things ruled the world in the Permian. So if you want to know anything about this stuff, it happens that we've got at CBU an expert, right? On the Permian synapsid. So you can go and harass, you can go and harass Sean Modesto, he's upstairs in the biology building. So go and chat with him, and you can ask him all sorts of questions. Now I want to point this one strange beast here out for a second. This is a thing called Arkosaurus. And this guy lived in the latest Permian. The latest Permian. And no, this is not a weird Photoshop thing. This is not super relevant to what I'm talking about. But he had this really odd overbite kind of thing going on here. But I want to, I'm gonna come back to this group here. This thing is called Arkosaurus. That's the name of the genus. It is an Arkosaurus form reptile. So this is an ancestor of a group that is called the Arkosaurus that we're gonna come back to in a second. Because the Arkosaurs are super important. So this is just a little critter scampering around in the end of the Permian. But his ancestors in the Triassic are gonna become super important.  I have no idea why it's morphology was like that. I'm sure if you Google it around, it has an explanation. But a very, very strange beastie indeed. Okay, so we are in the late Permian and it is a dry desert, bizarro world formed with these climate extremes because of the presence of this giant super continent with a huge mountain chain running right down the middle of it. So this is not a nice place to live. If you are, even I'm sure a Therapsid, you would probably be happier in a different world. But it gets a lot worse than that. So you remember when we looked at the five great mass extinctions, right? So here we have the Great Ordovician Biodiversification event. Then we have more or less a plateauing of diversity with these extinctions here, the Ordovician and the Devonian. This guy here is the undisputed king of all the mass extinction events. This guy over here, the incretaceous, gets all the credit because it killed the dinosaurs. But this guy here is the granddaddy of them all. And then note that really rapidly afterwards we get another one. So this is the end Permian and this is the Triassic mass extinction. Now I wanna note something and we're gonna talk about this later on very briefly. But notice that we have a plateauing of diversity here. After this mass extinction event, which absolutely decimates the world, diversity slowly comes back and then it keeps on rising to the levels we're at today, higher than the peak was up before. So here is a question that I am not gonna answer for you because we don't know the answer, but why is it that diversity seemed to have plateaued? There was a maximum plateau. Even when there was a mass extinction, it came back to a plateau. In the Paleozoic, right? But in the modern era, the Mesozoic and beyond, we were able to actually maintain more species on the planet Earth than we seem to have been able to in this previous several hundred million years. This is an open question. We don't know, right? There was some suggestion, this is a statistical artifact, but it seems not to be the case. This higher level of diversity here seems to be a real thing. So that is an open question in paleontology. One of these big questions, which are in deep ecology kind of questions, what are the mechanisms that ultimately limit the total number of groups that can exist on Earth? All right, I'm not gonna answer that question because we don't know the answer. But let's talk about the end-permian extinction. So you see various estimates all around the 90%. So this is an absolutely devastating event. In marine realm in particular, 90 plus percent of species died out. We're pretty much wiping the slate clean at this point. So the great dying it's often called, when life nearly died, here's a book you can go read about it. This is not an exaggeration. I mean, this is the most catastrophic event in biological history, with the possible exception of the oxygen holocaust around two and a half billion years ago, but that was a death of microbes. So we don't really care about that. But in terms of higher organismic history, this is a completely unprecedented before or after event, unprecedented and unreplicated. And let's hope it will never be replicated because this is a horrific event. So what is the cause? Well, anytime you try to work out the cause of any of these things in geological time, it's of course difficult to do because you often can't directly study things. I mean, it's a way in the past. So we're often one step removed. We have to use proxies. Often the way we date things have really large error bars, right? So if you wanna do a differentiate between two causes, the first thing you wanna know is what is the effect, right? So was it a rapid species loss or a more prolonged kind of event? And believe it or not, the jury is still kind of out on this. So this is a paper that came out in 2018, looking at the marine record and this one here. Most of the marine stuff, it was instantaneous in geological time. So they're actually talking a period of some tens of thousands of years probably. That's the limit of their resolution, maybe 30,000 years. But that is a rapid, a rapid loss. And we're talking about losing 90% potentially a marine species in a few tens of thousands of years. That is insanely fast. Now here's a paper that literally just came out last month and notice that we've got Sean Modesto down here. CBU Sean Modesto is a co-author. And so they presented geochemical evidence and some paleontological data put together looking at the terrestrial realm. And they wanna know, so there had been a suggestion that the marine and the terrestrial, so these are, you know, the ocean and things like the synapses going extinct, that these things may not have happened at the same time, in which case you would need a more complicated explanation. So they argue that these things were in fact synchronous events. But then just to make things complicated, I'm gonna show you that literally this just came out March 27th, we're a couple of days behind at this point. Here is a brand new paper that just came out which suggests that in fact that turnover, that the terrestrial die-off happened potentially 400,000 years, potentially 400,000 years before the marine die-off. So this is still where we are and we're trying to figure out exactly even what the direct effect was. I mean, nobody denies that we lost, you know, 90 plus percent of species, but exactly how the ecological systems of the world responded is still kind of an open system. And you might say, why would that be the case? Well, part of the problem, remember, is that we're actually building these timelines based on the organisms themselves. Remember, we're using biostratigraphy, but you can't directly correlate between, even in the marine realm, between a sequence of biostratigraphic fossils that we erect in deep water and shallow water. If the organisms didn't overlap, I can make a scheme with relative time within it, the deep water that may not, that is just not correlatable to the shallow water. If you're trying to compare between marine and terrestrial, figuring out exactly how the events correlate is really, really hard to the point where in the Triassic, it gets even worse in the Triassic. But anyways, this is where we are right now. This is still being fought out, but regardless, the bottom line is the world got absolutely decimated roughly 250 million years ago. So what would have caused this? Well, here's another one suggesting that there were two individual spikes within that 10,000 or 30,000 years, 60,000 year kind of die-off period of the marine realm. So the bottom line of what caused it in terms of ultimate cause, we're pretty clear on. There was a giant eruption. Remember when we talked about the Franklin igneous province as an explanation for snowball earth, the weathering of this? Well, when you've got the eruption of a giant igneous province or a lip, a lip remember we talked about a large igneous province, this can cause climate change in two different ways. The first is that this can weather and as it weather, remember weathering is gonna pull CO2 out of the atmosphere and bind it up. But the other thing is any volcano is capable of coughing material out and it's gonna push out both CO2 which is going to have a warming effect as well as in a short term, it's gonna shoot off little particulate material here which remember can actually deflect light and have a short term cooling effect. So volcanoes are capable of cooling in the short term from these sulfate aerosols. They're capable of warming in the kind of medium term from the CO2 and they're also capable if they are especially down near the equator where they're gonna weather really rapidly which was the case we think with the Franklin igneous province, they're capable of pulling CO2 ultimately out. So these are all kind of complicated ways that depending on the rate of eruption, the geochemistry of the eruption, where the eruption occurs, that volcanic material can interact with the climate systems of the world. So the Siberian traps were massive, massive. So to put this into perspective, somewhere around the order of seven million square kilometers were covered in lava. This is the size of all of the USA, of continental USA. That is huge but what this doesn't mention is the depth of these things, how thick these deposits were. So we put that into context and we've got somewhere along the line of here's Canada to remind you, this would cover all of Canada more than 300 meters deep. We estimate somewhere around three million cubic kilometers of material was erupted over a period of probably several hundreds of thousands of years with a few major pulses of eruption within there. To put that into context, this would bury the Eiffel Tower about 30 meters and it would bury almost, we just have the tip of the Empire State Building sticking out anywhere across Canada. That's how thick this would have been. So that obviously would have been bad on its own but there's an additional suggestion that where this eruption was happening, this large area, was an area that had huge amounts of coal, right? And other had carbon rich rock below the surface and so as that lava was erupting up, not actually on the surface but the layers of coal were kind of underground and as that lava came up and moved out, it would interact with that material, vaporize all of that carbon rich material which would then off gas out. It's not literally lighting on fire, it's vaporizing it through metamorphism and that would then cough out massive more amounts of CO2. So we've got not only this event itself but there's strong suggestion that it was also vaporizing huge quantities of hydrocarbons as well. So we're literally not only having all of the world's volcanoes erupt simultaneously but we're also burning massive quantities of fossil fuels simultaneously. So you can read, this is a 2017 paper that looks at this a little more in detail. It's a 2011 paper. So we think that was probably going on. There's a bunch of other complicated interplays that all tie back to our climate change discussion where we were talking about feedback effects. And I don't really have time but you can read some of these other here feedback effects but what would this have done? Well, the first thing it would have done is massively flip the climate off. The second thing it would have done is as the world's oceans start to warm, first, warm water can't dissolve as much oxygen in it but second, remember we've got these big conveyor belts. We already talked about these big conveyor belts where cold water sinks down here and it moves around and that brings oxygen from depth up and keeps things from becoming stratified. We talked about this in the Ordovician. So you potentially have the stratification of oceans and a drop in the amount of oxygen. So we actually have less O2 we think in the oceans. They're also getting massively hotter. At the same time, we are dissolving more CO2 and more sulfur compounds which is gonna end up massively acidifying the ocean which if you are something like a coral or you are a clam, this is not good for you. This is a problem going on actually right now on a much lesser extent. Ocean acidification is a problem with current climate change and there may have been dramatic feedback effects. You can Google these things but these are ways that initial warming may have kicked back and cause catastrophic runaway warming as well. So we're talking global warming. We're talking probably ocean anoxia and ocean acidification. On the land, we're gonna have runaway heat as well as massive changes in terms of the climate cycles. But the other thing is that as these volcanoes are erupting, remember that where they go through major pulses of eruption, we've got tons of that sulfate aerosol material going up and so that potentially is going to cause in the short term dramatic cooling and then once this material disappears which is just a few years, once it disappears, then suddenly we can flip back to super heating again. So we may have also seen crazy bouncing back and forth of climate. So we have seen potentially this crazy fluctuation back and forth between cooling and super hot back and forth regardless, this is not a nice scenario. So massive volcanic eruptions seriously messing with the ocean and the atmospheric system, runaway climate change, runaway transformation in terms of the ocean system. Everything we're seeing happening to the climate right now but orders of magnitude worse. If you wanna learn more about this, you can check this link out here. This is Peter Brennan. He is a science journalist who has just written this fantastic book which is an overview, a really readable overview that I highly recommend you read of all of those five mass extinctions, the kind of state of the science. It's only a couple of years old. Really check this out. This is an article that just came out going specifically looking at the ocean changes in the Permian, you could check that out. So what happened? Well, we lost a lot of things. We lost 90 plus percent of species but we completely lost the trilobites, those charismatic fossils. We lost all of the corals we've seen up to this point. In fact, every coral which is around today in the world is completely unrelated to the corals of the Paleozoic. We lost, these group we didn't talk about, they're called sea scorpions.  Everything else gets seriously impacted. 90 plus percent. Again, I wanna emphasize that number. This is a catastrophic event. So that is where we are at the end of the Permian and so that sets us up then for the rise, yes, of the dinosaurs. I promised you we were gonna get to dinosaurs except not quite yet. So we jump now out of the Paleozoic, right? Paleozoic era and we jump into the Mesozoic and so the Mesozoic has got three components. People talk about Jurassic Park all the time but we start with the Triassic, we run through the Jurassic and eventually we end off with the Cretaceous and there are the timelines you do not have to memorize these dates and here are the periods right there. So that is the Mesozoic, right? Remember the Mesozoic, that just means middle life, old life, middle life, new life over here. So there is the Mesozoic. So I asked you this question again and again, right? So in those forests, well last time we had what was in those forests, well, we literally had the earliest amniotes in the fossil forests of Joggan. So what is in these forests? Well, in the Mesozoic, yes, we do finally have dinosaurs. We've finally gotten to dinosaurs. So here is a beast, right? This is a terrifying beast. Look at the teeth on this, look at the stance on this. This is a thing called Postosuchus, right? This is at the end of the Triassic about the scariest thing you could have run into. Now this is a terrifying beast. It's known from a series of localities down in the States. Here's an approximate reconstruction. You would run really rapidly away. If this was you, you would be going that direction if it was going this direction or maybe you'd be dead because it has eaten you. So this is a terrifying late Triassic beast. And so is this an example of an early dinosaur? Nope, nope, this is not a dinosaur. So once again, the world is full of a lot more stuff than we are used to thinking it up historically. It is also in terms of an evolutionary story, a lot more complicated. So this thing was living beside dinosaurs, but it was not a dinosaur itself. So I can unpack that now and it's gonna follow a major or from it, it's gonna follow a major moral that I'm gonna have for this entire course, which is that the story of evolution involves a lot of chance interactions with environmental catastrophe. So anytime you see that sucus in it, it means that it is a crocodile or a crocodile lineage organism, except sometimes that word sucus is applied to something which is not a crocodile, but in original description it was, but the name just sticks. So generally speaking, if you see sucus on the end, you're looking at a crocodile lineage thing. So we're not a dinosaur yet, but I will get there. Here is another one of these PBS eons. These things are all amazing. Go check it out, it's 10 minutes long and it goes through kind of evolutionary reasons why a lot of these things that existed in the Triassic are super weird. So we come out of this massive extinction event and in the earliest part of the Triassic, we've still got who in charge, it's the Thrapsids, the ones who made it through the extinction continue to rule. This little guy here, Elistosaurus, is one of the classic ones. If you go talk to Sean or ask me, I'll bring you by, he has actually a skull of one of these in his lab that you can go and check out if you wanna go see what one of these things actually looks like. These things were quite common in the earliest Triassic. As we start to move in, we start to see a diversification though of the reptile lineage. So remember I'm gonna use the term diapsids and contrast it with synapsids. So the mammal lineage amniotes and the reptile lineage amniotes. And I'm using these terms, reptile, diapsid, et cetera, quite loosely in a phylogenetic sense to remind you. So this is a thing called euparkaria. So you look at this thing, what does it look like? Well, it kinda looks like a dinosaur, but it kinda looks like a lizard that you might buy at a pet shop. If you watch the walking with monsters and walking with dinosaurs, this thing makes a prominent appearance here. So this is not a dinosaur quite, but it is a relative or an ancestor of dinosaurs. So here is what Triassic dinosaurs looked like. They were cool, they are not yet the beasts that feature in Jurassic Park, right? But there are things like this prosaura pod right here. So this is an ancestor of the prosaura pods, right? This is an ancestor or its group was, right? So there's euparkaria. So it's an ancestor of the dinosaurs, but it is also an ancestor of the crocodile lineages. And you're gonna look at that and say Jason, that is not a crocodile. It is true that it's not a crocodile in the sense that you're used to thinking about crocodiles, but we have two large lineages. We've got the things that lead to dinosaurs and to birds, and then we've got the things that lead to crocodiles. But these guys were just as complicated as the dinosaurs. They just don't get their say in textbooks and in documentaries generally speaking. So here is a phylogenetic treat showing these two big lineages and you do not have to memorize this. What I would like you to know is that all of these things here, all of these things here are archosaurs. So archosauria, this group here includes all of the dinosaur and birds and it also includes the crocodiles and all of their relatives and their common ancestor. Those things are the archosaurs. So there's euparkaria over here, right? So this is a primitive archosauriform. And remember I showed you that weird overbite critter archosaurus as the earliest archosauriform. So these are the ancestors of this group here, the archosaur. And these guys are going to dominate the mesozoic. But it is not a simple story of the dinosaurs immediately taking off. It is not a simple story at all. So I am going to refer to these two big branches here. I'm gonna refer to these two big branches, our dinosaurs over here and our kind of crocodile group over here. I'm gonna call these the croc line and the dino line. These are not technical terms, but those are what I'm gonna refer to. So remember we had our synapsids and we had what I'm calling the diapsids. So the synapsids are a different branch that goes way over here. Then we've got this group here. It includes all the lizards. A subgroup of the lizards is the archosaurs. And within the archosaurs, we've got the dino line and the croc line. So let's take a look at what is in there. So look at these guys here and ask yourself how many of these things right here are dinosaurs? Take a look. So these are things, if you were to go in a time machine to the mid or late Triassic, you would see these, these are all archosaurs. How many of these are dinosaurs? How many, what do you think? One, two, all of them? This one kind of looks a bit crocodile-y, right? These ones look pretty, I don't know what that thing is. These are definitely dinosaurs, right? Definitely dinosaurs? The answer is none of those are dinosaurs. So which one of these is dinosaurs? Well, if you know your dinosaurs, you know Celophysis. This thing here is such a close analog, if you look at the exterior of it for Celophysis, that's what they originally thought it was. They had a bunch of these in plaster, they collected it, and no one bothered prepping them because they just thought, ah, I asked more Celophysis. Then when they actually started prepping it and looking at things like the hips on these, and they started to really realize, quickly, when you look at the interior, remember this is the Pimp My Ride aspect, right? That we build the exterior of an organism on a foundation, right? An evolutionary foundation, right? So, yes, evolution made a similar bipedal small animal, but if you look at what it was built upon inside, it's got the underlying architecture, not of the dinosaur lineage, but of, guess what, the croc lineage down here. As an aside, for you guys who are into art, this thing is named after Giorgio Keefe, right? Anyways, that is a side. So there's a Fidia O'Keefe. That's probably not pronounced right.  So there's our dinosaur. This guy down here is not a dinosaur. All right, if you want to go and read literally everything you wanna know about the rise and the fall of the dinosaurs, well, I would recommend that you read, hey, the rise and the fall of the dinosaurs. This is by Steven Versate, who is a young paleontologist. He's based in Edinburgh. He's an American paleontologist. He is not only one of the leading lights in the field right now, but he is a fantastic writer. If you want an aside, Bill Clinton said this is one of his favorite books of the year. Does that mean anything to you? Probably not. Don't know what it means to anyone, but it's a really cool recommendation to get. Anyways, this book is fantastic. I've got a copy if anyone wants to borrow it for summer reading. I guess with the coronavirus, I cannot lend it to you, but once those things go down, I would lend you one, or you can buy yourself. It's like 16 bucks or something like that on the internet. Check it out. Fantastic book. So I want to talk about some work that Steven did during his masters, I think. And this is one of my favorite studies. I find this really fascinating. So this is what we looked like as we moved into the late Triassic.  The world is full of things that look like dinosaurs. They look like dinosaurs. And what is represented in there? Well, you're not finding things like the giant seropods. They're not around yet, but what you do find are representatives of all of the three groups of dinosaurs. Here's the three groups, the Ornithicia, the sauropods and the theropods. These are the three big groups of dinosaurs, and they're all around by the end of the Triassic, as well as all of these weird croc-line archosaurs. They're around. They're all hanging out. And they are hanging out and competing with each other for roughly 30 million years until we get to this mass extinction event at the end of the Triassic. And what happens at the mass extinction event at the end of the Triassic? This happens. All of the groups of the croc-line, except the ones that actually give rise later on to crocodiles properly, they all go extinct.  All of these guys are dead, right? And which ones of the dinosaurs go extinct? Well, many individual species of dinosaurs obviously go extinct, most species of dinosaurs, but the groups themselves make it through. So representatives of each one of these groups make it through and they're then able to expand into the giants that we now see. I know that we don't now see, but I mean that we saw in the later Mesozoic. So does that mean that these guys were somehow worse animals that nature, you know, that nature doomed these guys because they were worse than the dinosaurs? Well, the answer to that surprisingly is no, not at all. So this is Steve's paper here. This is from 2008. So he looked at and he calculated how different, he came up with a way mathematically of representing how different the body plans were from each other. So, you know, if you look at this thing, this thing is obviously a very different organism than this thing in terms of the outside, the outside body plan, right? This thing's running on two legs, it's small, this thing's quadrupedal, the heads are totally separate. So he came up with a way of just measuring how different these things were. And that's a reasonable proxy because the shape of an organism represents what it does, right? Its lifestyle determines its shape, it engineers it. The earth itself engineers the shape by choosing the things that are best able to survive in any given environment. So this tells you something about its lifestyle. So by looking at the overall difference in shapes within the crocs over here and the dinosaurs over here, that gives you a rough estimate of how many ecological niches were being occupied. And what he found was that not only were dinosaurs not clearly better, they actually seemed to occupy less niche space. So I reached out to Steve yesterday and he told me this been subsequently been another paper that added in a bunch of new organisms and a bunch of new species have been discovered since 2008. And he said that their findings were a little bit different in that the sense that they occupy more niche space and they had greater success, the crocs, that apparently doesn't quite hold up but they are at least equal. So the crocs and the dinosaurs, the crocs over here and the dinosaurs, these things were equal to each other for 30 million years. They were at a stalemate, a standoff. Neither one was winning until what happened, right? This mass extinction event, this mass extinction event wipes out preferentially for reasons that we honestly do not understand. It wipes out the crocodiles and it wipes out most of the dinosaurs too but it spares some of them, one of every one of the groups of dinosaurs. And so after the mass extinction event, moving into the mass extinction event is here, here's the mass extinction event. So after the mass extinction event, the few representatives that survived in these groups were able to diversify into the world of Jurassic Park that you see in the movie. So all of these things, including every bird that came afterwards, expanded out of the few survivors. Why were those few survivors better able to survive than the crocodiles? We have no idea, no idea. But this was, this is one of the best lines, I think, that I've read in paleontology because it sums up so much here. So we think about the dinosaurs, the reign of the dinosaurs. So you're gonna see the dinosaurs reign for hundreds of millions of years, not hundreds, but well over 150 million years. The results or the reason for their preeminence is to a large degree, just luck. So there are the beneficiaries of two mass extinction events. Well, which one? Well, the end Permian wiped out all the synapsids and allowed the diapsids, the reptiles to take over. So that's mass extinction event number one. And then the end Triassic wiped out all their crocodile competitors and allowed them to take over all that empty niche space afterwards. That's mass extinction number two. And for whatever reason, we don't know. They were just pre-adapted somehow. Something about them made them better able to survive. They try asking extinction event in the crocodiles. Had things been different, we would be living in a world perhaps of flying crocodiles. That may sound far-fetched, but it's not unlikely at all. When you look at the degree of convergence of dinosaurs and their crocodilian relatives in other ways. So it turns out that if you wanna study this, Nova Scotia is again one of the best places in the entire world. Archaeology is amazing. So layered on top of, layered on top of this underlying older rocks, you know, of Meguma, Avalon, and Gandaria, right? That then got layered on top of all that stuff from the Maritime's Basin. We have some Mesozoic deposits. We don't have a huge amount. We've got little bits of Cretaceous, you know, little bits of Jurassic, but we've got pretty good stuff from the early Triassic and for early Jurassic and the late Triassic, which is when that mass extinction and the subsequent radiation of dinosaurs after the fact, the expansion, the evolution of dinosaurs after. That is well represented in this kind of chunk of land right over here. And if you wanna go and see this stuff, I'll show you in a second. The place you wanna go is the Funny Geological Museum in Parasboro, right about there. And if you are lucky or if you just ask very nicely, you might get to talk to Danielle, who is the curator of the Funny Museum now. She is a paleontologist, a vertebrate paleontologist from the US. The previous curator has now moved on to Halifax and that is Tim Fedak and he also still does active dinosaur digs there and that sometimes. In fact, you can do, they have a program in the summer where you can actually go and you can take part in dinosaur digs. So that is an amazing thing that you may wanna, if you've got a, you wanna spoil yourself for the birthday present, you can actually go out and you can take part in this. They've got some really neat activities there, really neat science going on. And so this is the museum here. It's right in Parasboro and there's Tim Fedak going out looking in these red, arid, early Triassic or late Triassic sediments and looking for these dinosaurs, right? They're on the cusp of the explosion, really of a bigness and dinosaur diversity. Go check this stuff up, hashtag, staycation. So much to see, honestly, in Nova Scotia. All right, so what caused the Triassic extinction? Almost certainly it was volcanism again. So this is really the theme that comes through all of our mass extinction events, right? The Permian mass extinction, definitely volcanism. The Triassic mass extinction, almost certainly volcanism. The Ordovician one, there was some strong emerging geochemical evidence of volcanism. It's still a little bit uncertain. And as you're gonna see in a second, the following extinctions, oh, the Devonian, that one, there's some sketchy volcanic evidence, but that one's probably the plants. But most of these ones, all of them were looking at climate change, but the big factor that keeps coming back again and again and again are these large igneous provinces. So if you wanna go see the large igneous province that killed all the synapses in that and the Permian, you've gotta go to Russia. If you wanna see the one that caused noble earth, you've gotta go to Arctic Canada. Where do you go if you wanna see the one that killed most of the dinosaurs and essentially all of their crocodile competitors? If you want to go see that, well, I've got some good news for you. I've got some very good news for you. You can go to Nova Scotia. So this is, again, an amazing thing. We've got Nova Scotia. So if you look at all of this area right along here, just outside of Wolfville, this is called, and all the way down to Digby, Digby Neck here. This area here is called North Mountain, the North Mountain Basalt. You can see that exact same material right over here. Really beautifully exposed on Partridge Island, just outside of Parasparo and beautifully exposed at Five Islands Provincial Park. So this here are those Triassic. These are Triassic rocks. You can see this red desert-y rocks in here. There's a big fault that divides these up here. So if you were to dig down here, you'd see red under here as well. That right there is the emergence of something we call the Central Atlantic Magnetic Province. So this is this major lip right here. And this is just the initiation of it. So this is the result of the beginning of the breakup of the supercontinent of Pangea. Pangea starts breaking in half, and as the process of it breaking open, it starts erupting lava everywhere. And you can see this, if you go down, these are the palisades. These are a famous kind of cliffy basalt deposit you can see in New York, New Jersey. So these you can trace all the ways from New York, all the ways up to Nova Scotia, to give you an idea of what the scale of this eruption was like. And again, here is a map that shows right here is that a map of what the original extent probably was, these red ones, this is actual outcrop of volcanic material we found. So all the ways down to huge portions of South America, most of the Southern states, the seaboard, this is where Pangea is rifting. You can see this is the edge of Pangea here, rifting apart. So massive, massive volcanism. So that volcanism did what? Well, it probably did the same stuff that to a slightly lesser extent, that the Permian did. So major climate change, potentially feedback stuff through say methane hydrates, I'm not really gonna talk about that. You know, ocean anoxia, all that kind of bad stuff that we saw happening happened again in the Triassic. And this nuked most of the, again, crocodile line and most of the dinosaurs, and ushered in a whole new world coming into the next period, which is the Jurassic. And in the Jurassic, we finally get into a Jurassic Park. Now, the joke, if you're a paleontologist, is most of the dinosaurs you see in Jurassic Park are actually cretaceous animals, but the Jurassic is really the beginning of the reign of dinosaurs. Now, dinos showed up, remember, in the Triassic, but we don't start getting these huge, terrifying dinosaurs until we get into the Jurassic. You would not wanna show down against a Triassic dinosaur, but a Triassic dinosaur, you know, these things were like llama size, you know, bigger than that maybe, but they were not the terrifying giant lords of the universe that we are going to see emerge in the Jurassic and the cretaceous. So now, moving into the Triassic or into the Jurassic, rather, with no competition in the Crocs, these things just start expanding across the whole world and they take over and they rule the world for about another 140 million years until, as you know, the end of the story, eventually the dinosaurs all die in another big mass extinction event. So I'm gonna invite you guys to go check this video out. It's 11 minutes long. It's again by PBS Eons. These things are fantastic. They're brand new, they're up to date. It is a great overview of the age of reptiles and the changes that we've had through these things as we move through the Jurassic, et cetera. Here is an overview. We've got a bunch of things here, like Thrysanosaurus over here, things you're not used to see, as well as in chylosaurs and stegosaurs, these beasts were Jurassic, these are Cretaceous. All these different dinosaurs, spinosaurs, there are hundreds of species of these. There's something like a new dinosaur species discovered once every week right now. So we get about 50 new dinosaur species a year. So these things took over the world and their overall story through that 150 million years is one that brings in the theme that we had earlier on. Remember we talked about allopatric speciation? That's where you get a group of organisms, you divide them in half with a geographic barrier and each one goes off on its own independent evolutionary journey. So remember prediction in our lab on biogeography was that you would expect to see an increase in diversity when you had an increase in boundaries, more isolation of things. So as Pangea starts to break up, we start to cut off populations from each other and so we start to get more what we call provincialism, which means that the animals that occur in this area are different than the animals that occur in this because they can't migrate back and forth and therefore they go on their own independent evolutionary journeys. And so as sea level went up and around things migrated back and forth, et cetera, but in general you would find very different organisms in different parts of the world and the disparity of them changed over time as continents moved apart and then came back together. So that is another tie in from things we talked about earlier on in the course. So we don't have any time to talk about this, but notice we haven't talked about the West Coast at all. We haven't talked about British Columbia, Alberta at all. That's because they literally didn't exist. We don't start building the West Coast or rather we don't start bringing the West Coast of North America on to the edge of North America really until we get into the Mesozoic. And in the Paleozoic there was a little bit, a few chunks arrive, but the vast majority of this material starts arriving in the Mesozoic from kind of the late Triassic on. And this is a crazy complex story that we just don't have time.  Remember our tectonic lab moving things up. So potentially even parts of Vancouver Island were brought all the ways up from down in Mexico through massive strike slip movement. That's a bit controversial. This is a geological map of British Columbia and you can see all these different chunks you also see that just like the East Coast of North America they're largely into colored lines like this. You can see colored lines. And that's because these represented individual micro continents that were slammed and accreted on the side just like Maguma and Gandaria and Avalonia were to the East Coast.  Even though I'm from BC, I don't know very much honestly about Cordillera and geology. On the other hand, if you wanna talk to somebody who does we've got an expert at CBU. So my colleague Deanne Van Royen, she actually did her PhD thesis up in the Rocky Mountains looking at the terrain history and metamorphic history of this region. So you can click on this link if you wanna read more just go and chat with Deanne. She knows a lot about this stuff. She knows a lot about a lot of things. All right, that's all I'm gonna talk about here. Let's just really briefly because we're wrapping this course up. I've got about 20 minutes left to talk to about another 200 million years of evolution. So it wasn't just dinosaurs. We have other groups, the pterosaurs, which remember are a reasonably close relative. They're archosaurs as well. These things evolve and they literally take off. So the evolution of flight. So flight, flying within the vertebrates first emerges in the Triassic. By the late Triassic we have things flying around. We've never had that in the vertebrates. We of course had in the Carboniferous we had insects flying around. First things like dragonflies and then things like cockroaches that could fold up their wings. But by the late Jurassic we've got these things flying around and they're gonna dominate the skies until the end of the Cretaceous. Now they aren't just the only thing out there but when I mean dominant, I mean they are by far the biggest.  I wanna show you for scale and this is not an exaggeration. There is a giraffe. This is one of the biggest known pterosaurs. If you click on this link, there's animation. There's actually a song somebody wrote about it. It's named after a, I think an Inca I forget, God of some kind. So I'm not even gonna try to pronounce that. I always get it wrong. I always learn it before each lecture and then I always mess it up. So I'm just not gonna do it but you can Google this if you want. I mean this is for the scale. These things were so large by this point they probably actually spent most of the time walking around. They probably had to launch themselves up using their wings as kind of pole, like a pole vault.  We think they actually did that with their wings. They kind of pole vaulted up. Anyways, these were giant organisms, right? Giant organisms. The biggest things that have ever flown, right? But of course we also get birds. So we get the, by the Jurassic, we get the pterosaurs showing up. By the Jurassic, we've got things like this guy here, Archaeopteryx. Remember we had Archaeopteris, which was a plant? This is Archaeopteryx, not to be confused with the backpack company. So this thing is right on the cusp of, you know, a dinosaur lineage and the bird, the avies, the bird lineage itself, right? This one's a bit controversial exactly where it sits. I haven't followed to see where they, they knock it back and forth between a true bird and not. I haven't seen where they put it right now. But we also get things like this. This is early Cretaceous, this Confuciornus. This thing here, if you looked at it, apart from the fact that it's got like teeth in there, this is a pretty normal looking bird. It's got this wicked double tail going on. These things are quite common and beautifully preserved in some lake deposits in China. Actually, I don't remember if it had teeth. Maybe I lied to you. It's got a beak anyways.  Maybe I'm misleading you. All right. So what else have we got within here? Here is Hesperornus I put up. This one's got a beak and teeth right here. This thing is kind of like the Lake Cretaceous equivalent of a Cormorant. It would have had exactly the same, you know, it's a diving bird. It would have had exactly the same lifestyle. It's kind of a Cormorant. You know, you can see it's still got some primitive characteristics right here. All right, the mammals are around, right? They've been around. The Synapsids haven't died totally out, obviously, because we're alive, but they really don't do much. They do a little bit more than you see. When you see movies, they're always tiny little rodents cowering in the footsteps of these giant dinosaurs. That's not quite true. There were a number of them. They were fairly diverse, but they were really small to the point where the vast majority of the studies of Mesozoic mammals are literally just done on their tiny little teeth. So this is the thing. This is the largest known at current Mesozoic mammal. And this thing weighed about 25 pounds maybe. So this is the size of a really large raccoon. It's smaller than a border collie to give you an idea of how big this thing was. This, by the way, that's eating a baby dinosaur? That's not made up. We've actually found a specimen of this that has a baby dinosaur, which is a new little hatchling in its stomach. So these things definitely preyed upon and they preyed back and forth, but none of these guys were big enough to take on any kind of serious sized dinosaur. These things were raccoon, badger size organisms. They were not very big. And they stayed like, they stayed no bigger than that through the entirety of the Mesozoic. What about the oceans? So the oceans in general, through the Permian, they're more or less, or the Triassic is more or less a continuation of the Permian, which is pretty dry, right? Limited seas. So we don't have a very good, fantastic fossil record because there wasn't a lot of ocean, right? We were still in the middle of this supercontinent. But as we start breaking it apart, we start making more shoreline and we can start preserving more stuff. But what we do have the Triassic, we see that after this Permian mass extinction, where we kill off most of the marine organisms that you would find if you were to look in any fossil deposit to that point for the 300 million years beforehand, almost all of that stuff is dead. And instead, you get the evolution of a whole bunch of new things. New groups of corals, new groups of snails, of cephalopods. So we get this group called the amenoids who really take off, they were big. They showed up in the Devonian, but they really take off. But we also have the shellless things, the squids and octopuses that we're used to, they start showing up. We get a huge expansion of things like snails and clams. Clams were a relatively minor group leading up to the end of the Paleozoic. They take off, right? The Brachyopods were the clam of the Paleozoic.  The amenoids here, you probably know these. This is this whole new group of corals, the Sclerotinian corals, right?  So why is this stuff all taking off? Why do you have this increase in complexity? Well, this is probably, and remember back to our Cambrian story about ecosystem engineering and also biotic interactions, arms race stuff. So in this, the aftermath, these things start competing for niche space. In particular, we have a real rapid evolution of shelled organisms and things that crack shells, right? So those things together have an arms race that drives diversity. So we get things like this. You know, the Decapod crustaceans start showing up, right? This is called the Mesozoic Marine Revolution because you have this rapid expansion of diversity. And in fact, it beats any level of diversity that the earth has ever seen to this point. The level of diversity of today's oceans higher than any point in the Paleozoic. So by the Triassic, we get the first lobster showing up and by the Jurassic, we get crabs, which are essentially lobsters that just learn to curl their tail under. If you ever get a crab, don't, because it'll hurt them. But you can actually, they actually have the tail. It's here, it kinda covers it up. You can actually uncurl it. It's just small now, like your own tailbone is small, but you can see that they're directly the result of these guys. If you wanna see something gone halfway in between, Google squat lobster and see a guy who looks like a lobster who's sitting on his own tail. Very strange organisms.  You have these arms race. You've got Mesozoic marine reptiles, the cracking teeth. You've got sharks that are cracking mouths. You've got the evolution of starfish, which use hydraulics to crack open shells.  These things are showing up. All this stuff's coming along. Anyways, that's the bottom line there. Is the Mesozoic marine revolution, this expansion in marine biodiversity, probably driven by the organisms themselves as they start to expand and compete against each other in this newly vacated niche space in the Triassic. What else do you get? Well, the ichthyosaurs are the first of the big marine reptiles. So we talked about these. They look like there's a white-sided dolphin, I think. This is an ichthyosaur. I mean, they're hydronamically almost identical. And yet they're completely unrelated. These are represents the diapsid lineage. These are reptiles and these are synapsids. These are mammalies and mammals, just like us. So we talk a lot in this class about biggest things, Canadian examples. So the biggest marine reptile, which has ever lived, is this thing here, Shastasaurus. And Shastasaurus is from British Columbia. You can actually go see it if you want. Here is a specimen of it. This is in the Royal Tyrell Museum, which you guys should all go and see. It's in Alberta. Some of you have probably been there already. And you can see a specimen of it laid out. It's absolutely gigantic. The plesiosaurus are the top predators and you've got these long-necked versions, but you also had short-necked forms like this for a scale. That person is about five foot two.   The mosasaurus, which you guys might have seen from the last Jurassic World, I think it was, this thing was way too big. This thing, they are really large, but they made this thing four times as big as it actually was. But they were terrifyingly large. By the time we get into the late Cretaceous, when things like T-Rex and Triceratops are walking around, these guys were the kings of the ocean. They're terrifying. And in fact, another Canadian story, if you want to see one of these, a large one of these, the largest one which is on display to the public, is this guy over here that they call Bruce and he is in the Morden Museum in Morden, Manitoba. You can go check him out. There's Bruce right here. He's 43 feet long. This thing is massive. This is like three or four cars parked back to back. Maybe even more than that. This is a huge organism. Now, this is boring, maybe, except for you who have botanical aspirations, but by far the most important change, really, that took place in the Mesozoic is the advent of flowers. Now, why is that important?  Is that true? Well, the group, Angiosperms, they represent everything from maple trees through to tomatoes, to grass. All of those are Angiosperms. Pretty much everything that is not a horse tail, which, remember, showed up in the Caribbean, ever since it still exists, or a pine tree or another conifer, pretty much every other plant, everything including cactuses to corn, all of that is an Angiosperm. And Angiosperms did not exist until the Mesozoic. So pretty much every group of plant that you can think of did not exist until the Mesozoic. This is an even more important change in the advent of dinosaurs. And it's one, unfortunately, we don't have a chance to unpack very much anymore. This is a diagram showing approximate number of species. And you can see that coming into, coming into the Jurassic, the world becomes dominated absolutely by Angiosperms, by this group here, which means that every kind of plant that was available changed, which obviously changed the vertebrate and the insect communities as well because the background, the base of the food system is radically changing. And in fact, there's this complicated interaction because as you know, many flowers are pollinated by insects that land within them. And so we see the evolution, the co-evolution of things like bees, termites, ants, all of these groups that we're used to thinking about is really being, and in fact, do dominate in terms of biomass, do dominate the insect world, these things also show up. And many of them evolve directly lockstep with the advent of the Angiosperms. So all of this stuff is happening and this is all very cool as well. And then we get another mass extinction event, the late Cretaceous or the incretaceous extinction event. This is a really old school reconstruction. I just like it. This is not how T-Rex stood. Look how evil he is, this red eye here. This is New York Cretaceous landscape. So those volcanoes back here are kind of foreshadowing, but we kill all this stuff. We wipe all this stuff out and the story, you can click this link, I'm not gonna get into it in detail, but you can look, these are the alvarez's, these are the people most closely associated with the mass extinction hypothesis of a meteor impact. So this definitely happened. We have 100% know confidently there was a massive meteor impact that hit down off the Yucatan Peninsula in Mexico, absolutely catastrophic. Would have had world-altering effects, potentially vaporized massive amounts of sulfates and carbonates, so rocks that have sulfur and CO2 kind of built into them. So potentially releasing huge amounts of gases and altering the climate. This would have just had devastating effects. Unfortunately, to complicate the story, at exactly the same time in India, we had another one of these giant lips, these large igneous provinces. So pretty much large parts of India are just getting covered in kilometers thick lava. And so there was an ongoing debate and it's really testy actually. It's a really emotional one. I've seen a few big showdowns. It's heating up again at conferences. Couple of last conferences I went to, I actually saw one where Gerda Kuller, I saw two presentations she was on, and she has stood up to a lot of abuse over the years because she has been pretty much single-handedly kept the dick and traps hypothesis for the extinction alive. There was a lot of vitriol and a lot of it misogynistic vitriol as well. But also having watched her, having watched her presentation, she can give as much as she takes. She is not the most tactful of presenters, which is understandable. Anyways, so this is ongoing debate. I'll tell you, I am a bystander, but I also see zero reason to really choose. This happened and we've already seen in the past that essentially every other mass extinction event that we have good evidence for is a climate change event. And the Triassic and the Permian are definitely large igneous province events. Those are the two ones that came before this. So any reason to think that this was not also a large component? No, I'm pretty convinced that this had to have played a role. But we also simultaneously got this giant killing blow right here. And there's actually a suggestion that they may have been interrelated that the seismic impacts of the seismic effects in terms of the ripple effects from the shockwaves may have actually helped amplify this volcanism, even though this took place on the entire other side of the world. Anyways, that's kind of a conjecture, but it's an idea people are playing around with right now.  And we can see that in the form of things like a fern spike, which if we look at the pollen record, we see that right after the mass extinction event, suddenly the entire world gets covered in ferns. Well, ferns are a taxa that come and take over after, say, a forest fire. So they take over when everything else dies. And so the fact that we see ferns show up everywhere is telling us that the entire ecosystem just self-destructed. So a lot of stuff died. The dinosaurs died. The ammonites died. I mean, a lot of the cool things died. All of the marine reptiles died. But a lot of stuff survived. Mammals survived. The crocodiles survived. The birds survived. So dinosaurs are still around in the form of birds. But the ultimate result was that most of the inhabitants of this world all went away. And immediately afterwards, this cleared the stage for the mammals who remember have been hanging out for a long time. They were the kings. Their ancestors were the kings back in the Permian into the early Triassic. When these things go away, that suddenly opens up space for the survivors, the mammals to recolonize. Now, why did the mammals colonize? We don't know. Why did they survive? Maybe because they were more adaptable in terms of their food sources. Maybe the metabolism was different. Maybe they were able to burrow underground. There's a lot of hypotheses, but we really don't know is the short answer. For whatever reason, again, just like the dinosaurs were better able to survive the Triassic extinction than their crocodile relatives, these guys were better able to survive the Cretaceous extinction than their dinosaur relatives with the exception of the birds. So where does that lead us off? Well, that's the end of the course really. But I do want to remind you that we stop at this point. This is 65 million years ago, 66 maybe now, million years ago. So this is where pretty much every history stops. But the rest of the world continued being awesome. And a lot of things came and went. This is a principle that I made up called the all the cool stuff is dead principle. Stuff is actually not the word I normally use. So this is the all the cool bleep is dead principle. So here's just a quick crash course through some cool stuff that's dead. Here's Megalodon. This thing existed for 20 million years. There's a great white shark which are terrifying. That's Megalodon. That is not an exaggeration. Unlike the Mosasaurus in Jurassic Park, they really were this big.  These are things that are culturally called terror birds. These things existed almost since the end of the dinosaurs up until fairly recently. They lived in South America and they were the terrifying apex predator in South America. They're essentially emus from hell. You look at the beak on this, there's a human being for scale.  So dinosaurs didn't die out. They were still around in the form of birds, but they were also a form around even almost in terms of morphology. We had things like that. We also had, until recently, human beings actually killed these things. These things existed and coincided with us. Elephant birds and moas. These things were massive, like one ton birds that used to exist until relatively recently. Mammals are pretty small now in terms of what they were like in the past. This thing was the largest land animal that ever lived. If you go to somewhere like the Field Museum in Chicago, go into the Hall of Mammals. Everyone skips the Hall of Mammals. They walk straight to the dinosaurs.  These are, this is a rhino relative. These are modern rhinos, which you know are massive and terrifying. Look at the size of this thing, right? 20 tons. These were massive. These lived about 30 million years ago through a particularly warm interval of time. These are basal sharks. This is basalosaurus. This thing eventually gave rise to sharks, to tooth sharks like orcas.   This is a thing called Andrew Sarkis. We know it from a single skull. This is the scale of the skull. Look at those teeth. Look at those teeth relative to this. A tiger's skull is kind of like this big, relative to this man's arm. Can you imagine the size of this animal? This is as far as we know the largest mammalian carnivore that has ever existed. Here is a thing, this was a lemur. These used to be diurnal lemurs.  But these things used to exist the size of gorillas until reasonably recently. And then of course you get this strange lineage of primates that show up and you are one of them. You are listening to my lecture right now. So these things start showing up around four and a half million years ago. We get primitive, we start getting primitive hominids showing up. And in fact, not only do we have fossils of these, but we have trace fossils of these. This is one of the most beautiful things I think I've ever seen. This is three and a half million years ago. This is ash. So this would have been a volcano, would have just been erupted. And look at this, you can see walking bipedal. And then what is this?  If you click this link right here, it takes you to a Smithsonian Institution page and you can go through, this is a slightly outdated picture, but it takes you through the complicated family tree of human ancestry. I'm gonna ask you nothing about this. But if you wanna go look at this, it's an amazing story. We find new stuff. There was a new discovery literally just this week. New discoveries all the time. All right, how I wanna close this off is just to talk about a really fundamental take home of this whole course. So we have, as geology has started to expand, we have had a shift towards a movement of calling things earth sciences or even this discipline here of geobiology. This is in recognition of these close interactions between the biotic sphere and the abiotic sphere, the way that organisms can help precipitate minerals. We make them ourselves in our shells, but they also do things like, bacteria will change the geochemical conditions in ground, in sediment and form things like pyrite. They literally changed the way the earth weathers, right? How rusting, they made rusting possible by creating oxygen. So this complicated interaction between the geosphere and the biosphere is something we've only recently come to realize. And it's something which is a really important lesson going into the new future. And the new future is one of climate change. What you should have taken from this class is that the climate has always changed and it changes for a whole series of mechanisms driven from in the long term, things like plate tectonics to in the shorter term, fluctuations in greenhouse gas concentrations. We are currently going through an interval of rapid climate change. Arguably more rapid than we've seen in several million years. And it is from the change in greenhouse gases. As we looked at earlier in the course, all of the other possible explanations have been eliminated. Other things are playing roles, but most of the things like orbital changes actually are pushing the climate colder. We are warming the climate. So human beings, biology is once again interacting and interfering with the geosphere. Except this time, we're doing it via combustion, not via some other biological process. We're doing it by burning things. And so understanding the lessons of the past are absolutely fundamental to understanding how this organism, the dominant organism in the planet today, homo sapiens, how homo sapiens is and will alter the geosphere and the biosphere going forwards. All right, this is the final slide.  First, science is made by people, right? Geology is a, and all sciences are an endeavor which is shaped by local individuals, you know, who work hard and put their hours into actual dangerous conditions. Chipping away the little bits of data. I did my part in my PhD, right? 10 years I looked through a microscope to generate a very small amount of data.  So it's built by people. And more importantly, I wanted to know it is built by all people, right? When you look at representations of geologists, it's usually white guys, we'll be honest. I've tried to show you in this class that there is a great diversity of geologists and paleontologists often who do not get represented. So it is a place for everybody. The second thing is this idea that we can learn about the past by looking at present observational processes. But there's a limitation to that because all of the processes of the world have evolved and they've evolved over time largely through the mediation of life. Life has literally changed the substrate. It's increased the number of minerals that are capable of existing on this planet by introducing oxygen. Chance plays a really big role. So these changes that happen, some of those changes are via life. Some of those other changes are from things like meteors crashing to Earth, right? You can't predict that. And there's no way of evolving to be prepared for that event. By chance, you might just get lucky. The final point is maybe the most important point in this entire class, which is that as we move into an uncertain climate future, understanding how ecosystems have responded in the past to climate change is gonna be crucial towards planning, adapting and mitigating the necessarily negative and terrifying effects of climate change. So not only can geology learn from the past, those lessons can be applied to the future. So that's the end of the course. I really invite you guys to check in with me. I can provide resources. You're always welcome by the lab, but I can also provide guidebooks, resources, advice for how to explore this amazing geological backyard that we have in Nova Scotia. And over a billion and a half years of the Earth's evolution is captured in our own backyard. I really invite you guys to explore it.