It’s worth noting that mammals were reaching megafaunal proportions very early in the Paleocene, to the point wolf-sized animals like Eoconodon were around less than a million years after the impact. So mammals didn’t stay small until the Eocene and then outcompete the giant birds and reptiles: mammals got big first and stayed dominant due to the tendency of niches to work on a “first come first serve” basis, and the giant flightless birds and land crocs and such evolved in that context to coexist with the mammals.
What you've stated up here is 'kind of' true, but only partially. This definitely did not apply for every region of the planet AND this definitely also did not apply for every niche even in regions where mammals were most successful. All in all, your OP is heavily oversimplified. P.S. - An animal sized like an average subspecies of today's Grey Wolf (40 to 50 kg) is nothing impressive, especially in comparison with what the Class of Mammalia produced after the times of Eoconodon, and it is controversial to call it "megafauna". You may then counter-argue by repeating here that it was indeed "impressive", because the given genus lived only about 1 MIL years after the K-Pg Extinction Event, but historically this is VERY normal/common; MANY much more massive animals managed to evolve seemingly out of nowhere (or sometimes rather out of 'nothing') within 1 MIL years or less numerous times before and afterwards. Plus, even during the time of the Dinosaurs some mammals could and did reach "non-tiny" sizes, such as 'Repenomamus Robustus', which weighed up to 15 kg which is the size of today's very large Eurasian Badger, or of African Wolf, or of the smallest subspecies of the aforementioned Grey Wolf.
Velociraptor I the monster raptor!!! Dilophosaurus I the monster lizard!!! Acrocanthosaurus I the monster giant reptile!!! it's coming!!! for dino gen!!!
I memorized periods and epochs for geological time and after about a year of casual study I am pretty accurate (for the main boundaries, forget about the sub-periods) but what I want for Christmas is a huge wall sized poster of the "Geological Time Spiral", that would be cool.
Well movember is now over so I’m afraid the stash is gone for another year! As for the next few weeks, I’ll be taking a short break from dinosaurs as I’ll be going through this period and the Neogene, but then the history of Earth will be done and I’ll be straight back into dinosaurs! Going to be doing a series where I go through various dinosaur groups so keep an eye out for that!
Presumably because they have small members, reproduce quickly, have little direct competition with other clades, and some have very generalist diets. All of which makes them good at surviving mass extinctions. Surviving a mass extinction is really about how good the species is in a mass extinction setting, rather than how good they are normally. Though, since small animals are favoured, lineages that can secure them tend to persist a long time.
@@dino-gen I do have a comment I like to add. Years ago I read they found triceratops fossils in rocks dating 13-20 million years after the asteroid. If true my thoughts my actual be right. I think many of the Dino’s died right after but some did survive past asteroid for some time only to be out completed by the smaller mammals. Reason I think this is many Dino’s we’re small as mammals at the time. Flying reptiles included. But as the climate probably cooled off over time and weeded them out. You said in video that fish didn’t suffer as bad so there would have been plenty of food for smaller marine reptiles to eat. But if the climate cooled for a period it would have been bad for them.
