Dimetrodon: YDAW Archive (Re-upload + Corrections)

[Music] foreign [Music] [Music] [Music] [Applause] [Music] this isn't a dinosaur [Music] all right you see dimetroduct this is clearly a dimetrodon by the way you see dimetrodon in a lot of dinosaur toy sets because it's a prehistoric reptile and it sort of has fit into the dinosaur category in the popular culture more so at least than you know woolly mammoth or the Smilodon or what have you was not a dinosaur it was a synapsis what's a synapse did you ask well a synapsid is an animal with a synapse a synapse is uh take your fingers put one uh right behind your your orbit behind your eye uh on your temple that's what this is called it's called your temple and then uh one behind your cheekbone on the fleshy part of your mouth there and then squeeze and you'll feel this Ridge of bone going back towards the top of your ear that is your synapse congratulations your synapse said you are more closely related to dimetrodon than dimetrodon was to any dinosaur that ever lived reptiles diverged at the beginning of the Permian period right before this guy showed up about 300 million years ago this guy would have been 290 to 270 million years ago that diverged into those that had two holes in their skull and those that had three scratch that those that had one hole in their skull and those that had two I was counting the orbit when I counted those up but I wasn't counting the nose so anyway you have synapsids which are these uh and diapsids which includes all living reptiles and birds and I mentioned this was the Permian period that was you know geologic period before the Triassic and dinosaurs did not show up before the Triassic so this fellow died off 40 million years before dinosaurs ever even appeared on the scene the world was very different then it was cooler but warming up Pangea had only just formed so the the climate was changing rapidly and this guy thrived in an environment where you didn't really have to be mobile or particularly efficient in order to make a living as top predator which we figure it was because it's rather large it was what 10 meters long at most I think I mean 10 feet 10 meters would be really long yeah 10 feet so in addition to being separated you know relationally in the tree of life and by time period they're also separated physiologically the most obvious difference is the Skull and I know it might seem kind of arbitrary to say well there's two lineages of land vertebrates and they're differentiated by a hole in the skull but that's the point of Divergence uh archesaurus had that extra hole in the front and it made their skulls lighter and they were able to be more mobile uh that was not their only Mobility adaptation but it was an important one dimetrodon had a rather solid heavy skull on it and they they have the skull a little incorrectly shaped there there should be more of a swoop going up towards the snout and the the premaxillary bone the very front of the mouth has this sort of snaggletooth thing going on speaking of the teeth dimetrodon means uh two measures of tooth which is weird because it actually had more like three it had basically incisors at the front of its mouth and then what we would call canines but apparently they weren't true canines and then it had smaller teeth going towards the back of the mouth this is in contrast to you know archesaurus or any dinosaur except heterodontosaurus hence the name because dinosaurs would tend to have one type of tooth per mouth unless they had a beak in which case they would have beak and teeth which is kind of a clever way of getting around that if we can call macroevolution clever speaking of the snout uh there's evidence that there's these ridges on the the top of the snout where where there that could have been an attach point for a cartilage structure so even in such an early synapsis we're already seeing the very beginnings of what we would call a nose uh it probably only looked like any other reptile but that's another Divergence from dinosaurs which you know pretty classic uh skin stretched over the top of the skull snout going on with them getting into the gate the the posture of the creature uh probably one of the reasons that dimetrodon is so popular to include with Dinosaurs is that it fits so well into the the conception of dinosaurs as sluggish sprawling lizard creatures because that's sort of what this was it was active but it wasn't particularly mobile like it had the sprawling gate like a lizard it would lift its body up to move but it rested with its body on the ground whereas dinosaurs and mammals uh have their legs under them to rest not to sleep necessarily but to they don't have to lift up to move and then set down to to rest they're much more efficiently built he's got a pretty robust tail too uh dimetrodon had a rather long tail like one third to one half of its length uh was tail but it was skinny it was even that was slightly mammalian looking what we would call mammalian looking with the uh sort of maybe dragging out on the ground but probably just holding it slightly off the ground whereas a dinosaur would be using it for balance it would it would be this big S curved muscular thing and there's a lot I could say about the difference between a dimetrodon's hip and a dinosaur's hip but I've talked so much about dinosaur hips already you can probably imagine ankles too for that matter point is after the Permian traffic Extinction which is when you know 95 of all life on Earth was dead that's when dinosaurs were able to emerge this guy and most of his descendants and all of his ecosystem had to collapse in order to create a world in which dinosaurs could Thrive because they were more efficient and and capable of existing in that sort of post-apocalyptic Wasteland that was the early to mid Triassic which is all I can really think of as far as dimetrodon not being a dinosaur this has been your dinosaurs were wrong thank you for watching please go to the geekgroup.org to find out who you can become a member and donate you could even like comment and subscribe comment with dinosaurs that you'd like me to take apart uh you could even send me a toy dinosaur to have on the show our address is in the description we will see you next time [Music] so I'm fairly confident in saying that that was our worst episode both because I was much more concerned with dimetrodon is not a dinosaur than with covering dimetrodon in any kind of detail for its own sake and because I didn't know a lot about dimetrodon I still don't but I was kind of completely wrong on some things and missed some Nuance on some other things I also misspoke a whole bunch we would just do a new take nowadays if I messed something up like saying meters instead of feet but I was just swinging for the fences back then just yeah I can characterize the amniotes radiation with almost no prep sure uh turned out about as well as you might think amnio's actually split before the Perman this would have been at the end of the Carboniferous and diopsis is not a wrong term to use but synapsides and sauropsids are much more stable terms to use but yes synapses do have just the one fenestra whereas soreopsides ancestrally have two but then if you look at any particular group they may have lost one or gained more so it's not a particularly useful way to identify a later skull but in the Permian it can still help us foreign 's activity and Mobility level were probably not as low as I characterized them it wasn't on the level of like a bivattle dinosaur obviously but not the sluggish unable to haul its weight around Hulk that I portrayed it as we have skeletal evidence that they would have had higher Energy Efficiency than we might expect when when moving and there's trackway evidence from a related animal called dimetropis which I believe is just an echnotaxa showing an animal like this walking in an approximation of the semi-sprall and posture that Crocs will adopt this is sometimes called a high walk I did this throughout the episode I would talk about it like it's a failure of an animal where it would Tire easily and have to lay back down after any burst of activity and that doesn't seem to be the case I neglected to mention that dimetrodon actually varies in size between species really substantially we have little tiny dimetrodon tutones which is 0.6 meters long the focus of our episode was to Metron grandis which is 3.2 meters long and then dimetrodon angelensis is all the way up at 4.6 meters long there might be more exceptions than not to the statement that dinosaurs tend to only have one type of tooth in their mouth like that that is just a bizarre thing to say dimetrodon's teeth show this interesting variation to them where some species have just smooth carne which are the the cutting edges of the teeth but then dimetrodon limbatus which I think is the type now has wrinkles in the enamel forming a sort of partial serrated Cutting Edge and then dimetrodon grandis shows true zyphodon dentition which is where the dentine and the enamel are involved in making the serrations and so independently this one species hit on the type of tooth that's going to dominate life for hundreds of millions of years while we're on the teeth I in my animations showed the teeth really poking out of the mouth like even when it's closed you would probably see those teeth out beyond the external tissues I couldn't find any information on like what osteological correlates we would be looking for in these animals I'm not familiar with the facial tissues of synapsids but as far as I know based on extant phylogenetic bracket we would expect the teeth to not be showing when the mouth is closed which means that that Notch at the front of the mouth would be obscured by the extra oral tissues I elected not to really change the posture of the neck compared to this toy or this toy for that matter which does the same thing where it's this old-fashioned dinosaur looking way to hold the head but um these objectively worse toys actually are closer to reality dimetrodon had an extremely short neck it was only five ish cervicals the in life the head would have looked kind of like it's it's squished and continuous with the body decently muscular neck mind you like it plenty to work with it's just not this dinosaurian looking posture and proportions which I wonder if portrayal like this might have contributed to the dimetrodon is a dinosaur misconception [Music] I caught this error in post but the nose of dimetrodon Bears elaboration no pun intended inside the sinus cavity are these ridges on the bone which are probably attachment points for these cartilaginous structures called nasoturbinals they are an adaptation for the sense of smell you occasionally see dimetrodon restored with an external cartilaginous nose like a mammal-like nose as far as I know that is incorrect the mammal movable nose evolved stepwise by replacing the premaxilla with a bone called the septomaxula and dimetrodon has a septomaxula but it's tiny and it's entirely inside the nasal chamber the premaxilla is still the main event when it comes to the snout tip of dimetrodon so I was sort of correct in saying that it was taking the first step towards a mammal-like nose but like on accident while we're talking about senses there was a paper this year actually which has some bearing on dimetrodon's hearing so none of these toys as far as I can see show a external ear not even just a simple hole historically dimetrodon has been thought to have pretty poor hearing below a thousand Hertz you know only really able to detect vibrations through the ground not so much vibrations through the air this is because there's debate as to whether they would have had a tympanic membrane an eardrum but the bone that we have that vibrates against the eardrum the stapes in dimetrodon was this huge strut supporting the brain case so probably not used for transmitting sound however this year workers CT scanned the back of a dimetrodon skull and found structures that would be used to pick up sounds at like 2750 Hertz you know way higher than was previously thought so how did they do that there's a process on the Jawbone that if they had a tympanic membrane maybe could have vibrated against that or maybe it just vibrated the jaw muscles to like approximate the function of an ear but in any case their hearing was not anywhere close to like a modern predator's hearing but it didn't need to be they weren't competing with modern Predators their hearing was better than other animals at their time I called the long skinny tail mammal like I don't know why I was so insistent on like any feature that we see here I want to talk about why it's more mammal like than dinosaur-like other than like that was the closest thing to a thesis I had but what's interesting about dimetrodon's tale is that the super long sort of serpentine restoration might be an over correction see originally case described a specimen now referred to dimetrodon grandis which only had the first 11 caudles 10 caudels preserved and they decreased in size really quickly as you went down the tail so he figured oh well if that keeps going like that there's not going to be more than maybe 20 caudals so you wind up with this very short like bob-tailed Dimetrodon then Romer came along in 1927 and said no I have this portion of like 20 coddles from the middle portion of the tail and while they're shorter top to bottom and and smaller in circumference than the more proximal caudals they're they're still pretty long so Romer restores them with this really really long tail I do like how Romer observed correctly that reasonable extrapolations from limited information can be overturned by new fossil data but then in the very next sentence extrapolates and says well they don't seem to be slowing down so I think that the tail extended well beyond the 40th caudal which In fairness like modern Restorations still have 50 caudals but if you scale romer's medial portion of the tail to the size of those last few caudals on cases specimen you wind up with an animal with a lot of tail vertebrae but a relatively short tail also this could have easily varied between species like everything else did I brushed right past the hips and ankles probably because they confuse and frighten me if you're used to the parasaginal way that dinosaurs stand and move dimetrodon looks very weird but their hip resembles a like very chunky lizard hip it has prominent muscle attachments on the pubis and ischium clearly plenty of leg muscles to move around with the acetabulum has a pretty wide range of motion which is good since the knee doesn't at least the knee can't rotate their ankles functionally are similar to crocodile angles in that they can both rotate forward and back and rotate around but that might be convergent because I don't the way that ankle bones ossify confuses me but it seems like they had the motion necessary to be able to both shuffle along with their legs sprawled and do the semi-spralled more active posture I implied that dimetrodon like just couldn't hack it it was kind of a failure of an animal that was just waiting around for the arkosaurus to come and supersedic which is like shame on Stephen for saying such things because first of all that's something that historical workers thought about dinosaurs you know that they're just waiting around for mammals to supersede them and I've railed against that before but also I was blithely repeating something that early workers also thought about dimetrodon um we touched on this in the Sophie episode there was this idea that as a lineage of animals ages it kind of stops adapting to its environment somehow and just like starts developing display structures that are useless to its survival there was actually a term for this four dimetrodon specifically the spinescence which is senescence and spines Portman 2. obviously the grand sweep of evolution cannot be characterized as just later forms are better animals are adapted to their environment also I kind of implied that dimetrodon was killed off in the great dying that is not the case they disappeared by the middle of the Perman they were extremely successful apex predators for like 20 million years and roma actually observed this he was criticizing The spinescence View and he said if dimetrodon is senescent decrepitude would appear to be a blessing [Music] since we're at the spines now um most of these toys show the sale continuing onto the tail as far as I know that is not correct the neural spines on the base of the tail are long but not so long that they reach the uh the ornamental scale of the ones over the back or over the hip also the ones on the sacrum and the posterior portion of the Torso curve backwards the ornamental spines do so you wind up with the rear edge of the sail sort of overhanging the tail but not being attached to it the biggest change from the historical portrayal of the sale came in 2012 when a paper by rega and co-authors found that the tips of the neural spines actually extended past the fleshy Sail by some amount now they were looking at dimetrodon Gigan homogenees so what they found there might not necessarily apply to every species of dimetrodon they were looking at the tissue of the spines and found that there were three distinct zones towards the base they are adapted for tendon and muscle attachments so you probably wouldn't see this really sharp division between the back of the animal and the sail it was probably a more gradual or stepwise transition then in the middle of the spine where it's got these Sharpies fibers that correlate with having flesh or membranes between them broken spines which seemingly happened fairly regularly would heal more or less straight so they had tissues splinting them whereas in the more distal portions of the spines broken or bent bone heals at all kinds of wacky angles and the way that the muscles and tendons of the back integrated with the proximal portions of the neural spines actually resisted bending and meant that when the animal's spine was undulating side to side as it walked it lost less energy to that bending it was an adaptation for Mobility or at least the proximal portions of the spine where the the distal portion was probably for display see rega also found that the way that the spines grew was to remain somewhat short while the while the rest of the animal was growing at a pretty steady slow rate the spines had a distinct growth spurt and they don't know if that's the animal reaching sexual maturity or reaching a position of social dominance but in any case seems to be a social signal rather than just some kind of metabolic need or such like [Music] most of these toys including the one we originally featured have a pretty like shallow torso uh that's not the case ribs 9 through 13 were quite deep on dimetrodon though some historical depictions take that a bit far Scott Hartman made some observations about dimetrodon's torso specifically the way that it would have held its spine and he showed that having it be pretty straight or having you know just a gentle curve uh seemed not to be the case he reconstructs it with more of a up and down more derived the rapid looking posture I don't know enough about these animals to say what that would imply but it sure looks neat and it squares with the way that the spines Bend because they're they're not actually straight up and down like most of these toys portray them they have distinct Fanning out and bending the spine the way he did lets them be more evenly spaced I didn't talk about integuments at all but um all of these toys except for the really low effort ones show a tuberculous scaly pavement um I don't know if that's accurate see we have traces from other non-therapisted synapsides say that 10 times fast where we know that they would have had scoots on the belly but then beyond that they had scaleless just mammal-like skin and I don't know to what extent the whole rest of the animal would have been just wrinkly uh scaleless skin or maybe it had other scoots elsewhere or maybe it did have patches of tuberculate pavement we know that you know parts of its skeletal Anatomy were not just in between reptile and mammal it was it was a mosaic of some features that are more reptile like and some features that are more mammal-like and probably its integument was no exception but that's another thing these are not just like a first draft of an animal these are not just some primitive template that was left to be improved upon these were the first fully terrestrial amniode apex predators if you'll excuse the overly specific superlative but they were experimenting with some adaptations that would be successful for hundreds of millions of years convergently mind you but just because their successors did some things better doesn't mean that dimetrodon was a failure and I shouldn't have implied as such dimetrodon probably merits a revisitation in a in a full proper your dinosaurs are wrong episode but for now this is what we've got so thank you for watching this your dinosaurs are wrong archive remember to like comment and subscribe and we will see you all next time we would like to send a special thank you to these individuals who have gone above and beyond to support this show we could not have done it without you thank you thank you [Music]

Channel: Your Dinosaurs Are Wrong

Views: 73,700

Keywords: ydaw, your dinosaurs are wrong, steven bellettini, dinosaur, dino, dinos, dinosaurs, triassic, jurassic, cretaceous, period, cladistics, taphonomy, therapod, therapods, sauropods, sauropod, fossil, fossils, skull, pathology, feet, hands, claws, teeth, jaw, anatomy, paleo, paleontology, climate, environment, science, educational, kid safe, kid friendly, child safe, child friendly, parody, fossil record, tail, hips, anatomically correct, mounted bones, museum mount, paleotube, paleotuber, dimetrodon, synapsid, diapsid

Id: 8Sqqb-u4Mho

Length: 27min 29sec (1649 seconds)

Published: Tue Jun 27 2023