so dinosaurs are cool hot take the fact that these wildly different creatures roamed the earth millions of years ago is not only awe-inspiring but terrifying one thing that has stood out to paleontologists is the seemingly odd rule that carnivorous dinosaurs are either really huge like the tyrannosaurus rex orally small like comp cygnus you know those creepy ones from jurassic park that look all cute and cuddly at first and then they go nuts stay away take a look at these two diagrams first looking at modern day carnivorous land mammals from kruger national park in south africa from lions and leopards all the way down to things like the small spotted genet you can see in this ecosystem the size of these animals is distributed across a gradient pretty evenly and this is true of other geographies as well they all fill their own niche with their own prey targets but now take a look at the scale of these carnivorous dinosaurs all found in the dinosaur park formation in alberta which have been scaled to match the largest mammal above and you’ll quickly notice a massive gap in the middle for perspective if the modern carnivores were similarly distributed there would be no carnivores between the size of an african lion and a bat-eared fox on top of all this our understanding of dinosaurs is that there were way more large carnivorous species than there were small which is the opposite of what we see today in land animals it tends to be lots of diversity in small organisms lower diversity and medium-sized organisms and then very low diversity in large organisms which makes sense based on energetics so the smaller you are the less food you need and the more you can kind of partition your ecosystem dinosaurs are the exact opposite when we look at them at a global scale most of them are big to understand this phenomenon we first have to look at the fossil records dinosaurs weren’t super diverse compared to the tens of thousands of mammals and bird species we see today there are maybe only around 1 500 known dinosaur species and of these species a lot more were over 1000 kilograms than under 60 kilograms but least of all very few carnivorous dinosaurs existed between those two sizes especially around the cretaceous period which is 145.5 to 65 million years ago turns out there’s something really unique about massive dinosaurs their babies are small now that may not surprise you lots of babies are small but it has more to do with the fact that they’re egg-laying creatures oviperous animals are those that lay their eggs with little to no embryonic development inside the mother and so dinosaurs started out weighing no more than 15 kilograms but a t-rex adult can grow to be 7 000 kilograms compare that with a larger animal today like a giraffe which weighs around 68 kilograms when it’s born and ends up around 800 kilograms as an adult an egg can only be about the size of a football because of how gas is exchanged through a shell even a sauropod that is getting up into the 80 ton range is just immensely huge are still being born like your average border collie size so how does that impact the size of other dinosaurs the theory is that these baby t-rexes would have had an almost entirely different diet than their parents because they were physically so different and because of this as they became teenagers they would actually be competing for resources with other medium-sized dinosaurs a niche that would have contained different foods than what an adult t-rex was eating for example a young t-rex likely couldn’t take on a triceratops because they were much more slender than adults only turning into bone crushers after a teenage growth spur and so they instead would go for something smaller and it looks like they simply just out-competed other medium-sized dinosaurs of course those teenagers would eventually grow up into adult t-rexes but their population as teenagers would have had a massive impact on other dinosaur communities and the ecosystem at large so then why don’t we see this gap in herbivores they lay eggs too and grow to even more massive sizes it’s more likely that their young simply ate the same foliage as the parents after all you don’t have to put up too much of a fight to take down a leaf though i will say rose thorns terrifying don’t wanna be near them don’t wanna get in a fight either way for herbivores the food barrier just isn’t as high herbivores have their have the opportunity to partition their resources and their ecosystem vertically so they can move up and down in a tree so a big tall sauropod can be eating at the tops of the trees while a teeny tiny baby sauropod can be eating at the bottom of the tree so they’re not necessarily resource limited in the way that carnivores are resource limited because a carnivore they’re going to have to be competing with one another that explains in part why we don’t see it in herbivores because of this some even suggest that juvenile megatheropods like the t-rexes could be considered their own species in an ecological type of way obviously they’re technically the same species but because their diets and impact on the ecosystem is so different than an adult in that way they’re almost like their own species in fact when researchers added juveniles as their own species into their models the gap in sizes suddenly disappears which helps further support the theory that the juveniles of megatheropods were actually out-competing other medium-sized dinosaurs ultimately leaving a gap in the diversity of species it wasn’t that there were no medium-sized dinosaurs per se it was that the big guys teenagers were simply taking their place speaking of huge i want to give a huge thank you to today’s sponsor skillshare who’s giving a free trial of their premium membership to the first 1000 people who clicked the link in our description go quick click it skillshare is an amazing online community where you can be inspired to learn something new from your own home it’s truly become a vital part of my life they have so many different classes of all different topics and i highly highly recommend it one of our favorite creators marquez brownlee or mkbhd just released a class called youtube success script shoot and edit with mkbhd which is a deep inside look at the creative process with one of the best creators on this platform also one of the nicest truly one of the best i 100 recommend that class but there is such a huge variety of subject matters from lifestyle art to web design their platform is dedicated to learning so there’s no ads they’re also always launching new premium classes it’s definitely worth your money again the first 1000 people who click the link in our description will get a free trial of premium membership you checking out and supporting our sponsors actually is a great way to help support our show and allow us to keep making videos thanks again for watching make sure you like the video subscribe and we’ll see you next time for some more science peace Video source: https://www.youtube.com/watch?v=qy9RKFaA-3Q
