Why birds and not dinosaurs?

So one of the main theories about why birds survived the mass extinction, but not dinosaurs is because the birds were smaller. But does that really make any sense? There were numerous small species of dinosaurs around, and numerous large bird species around before the asteroid impact. If size were the limiting factor, then wouldn't some toothed dinosaurs have made it through to present? Is it more truthful to say beaks vs. teeth were the true filter for the extinction? And if so, why would beaks allow them to survive an asteroid impact?

10 Answers

Relevance
  • Diana
    Lv 7
    1 month ago

    Only the smallest 2-legged dinosaurs survived the impact, because they were able to dive underground and escape the fires that engulfed the Earth.  Those survivors eventually evolved into the birds that we have today.  In fact, some of the ancient dinos had feathers, including the T-Rex.  Up in Canada, some dinosaur feathers were found encased in amber.  However, these ancient feathers hadn't evolved to the point where they would allow the dinosaurs to fly.  However, scientists were able to find out what colors that they were.  

    Source(s): In-depth library book research. Science magazines.
    • ...Show all comments
    • Ray
      Lv 6
      1 month agoReport

      All bird families were already evolved during the age of dinosaurs. 
      Archaeopteryx
      Confuciusornithidae
      Enantiornithes
      Euornithes (true birds)
      Patagopteryx
      Hesperornithiformes
      Ichthyornithiformes
      Neornithes  
      KT extinction killed all of them except for a few neornithes. Also killed most mammals.

    • Commenter avatarLog in to reply to the answers
  • Paul
    Lv 7
    1 month ago

    It is much easier for birds to escape environmental disasters. If a large volcano erupts, it can wipe out all mammals within several miles. But birds can just fly away to a safer locality.

    • Commenter avatarLog in to reply to the answers
  • 1 month ago

    because birds are so much cooler?????

    • Commenter avatarLog in to reply to the answers
  • Ray
    Lv 6
    1 month ago

    Any warm blooded animal bigger than a rat likely died out. And if said animal was also too much of a specialist, it also died out. The only ones to survive were practically something similar to rats and pigeons. 

    There used to be small nonavian dinosaurs and pterosaurs, but late cretaceous birds filled most of those niches, name me one dinosaur species that was that small. Cold blooded reptiles did better, they need far less caloric intake, thus they initially inherited the world [titanoboa filled a megafauna niche].  Here are the 8 known clades of birds: Archaeopteryx, Confuciusornithidae, Enantiornithes, Euornithes Patagopteryx, Hesperornithiformes, Ichthyornithiformes, Neornithes.  All died out except for a few small neornithes, which were not the most dominant bird clade in the cretaceous. All modern birds are neornithes.  There were 3 mammal clades that also went extinct even though all mammals were tiny back in the day. Only small generalist monotremes, placentals and marsupials survived. 

    • Commenter avatarLog in to reply to the answers
  • What do you think of the answers? You can sign in to give your opinion on the answer.
  • 1 month ago

    Omnivores, insectivores, and carrion-eaters survived the extinction event, perhaps because of the increased availability of their food sources. No purely herbivorous or carnivorous mammals seem to have survived. Rather, the surviving mammals and birds fed on insects, worms, and snails, which in turn fed on detritus (dead plant and animal matter). The largest air-breathing survivors of the event, crocodyliforms and champsosaurs, were semi-aquatic and had access to detritus. Modern crocodilians can live as scavengers and survive for months without food, and their young are small, grow slowly, and feed largely on invertebrates and dead organisms for their first few years. These characteristics have been linked to crocodilian survival at the end of the Cretaceous.

    • Commenter avatarLog in to reply to the answers
  • 1 month ago

    They might have wiped themselves out. They depleted and destroyed everything, until there was no more! I dont think they left in piece or because something hit them. They probably fought each other until the bitter end.

    Who ever could survive in caves and water lived on.....

    • Commenter avatarLog in to reply to the answers
  • Anonymous
    1 month ago

    Most birds actually did not survive the end of Cretaceous mass extinction. The dominant land birds of the Mesozoic were the enantiornithine birds, also called opposite birds because their leg bones fuse in the opposite direction of modern, living birds. They dominated most land habitats, except shoreline habitats, which were occupied by the ancestors of modern birds.  The enantiornithine birds were completely wiped out. Not a single species of living birds is an enantiornithine bird. Why? The key word here is land. When the giant meteor struck the earth, it resulted in ambient temperatures on land that were oven like according to geologists, because the impact packed the energy equivalent of 1 billion atomic bombs exploding all at the same time.

    No animal can survive oven-like temperatures. Some 75% of all species vanished. Most of the survivors were land animals that spent a lot of time underground.  They include lizards, snakes, toads, shrews, pill bugs, multituberculates (now extinct mammals that lived similarly to rodents), and salamanders. They survived because forestry scientists tell us that heat rises and therefore during modern day forest fires, animals like lizards, snakes and rodents can stay cool just by being a few inches below the ground and avoid being killed while big animals like deer and bears have to run for their lives. Because the impact created global temperatures that were oven-like as well as world wide forest fires, no land animal, regardless of size, has anywhere to run to avoid being killed practically instantly. Even if there were small dinosaurs, they would not survive if they were not underground.

    Besides animals that spent a lot of time underground, another group of animals survived because they spent a lot of time in or near the water. These animals include the duck-billed platypus, the monitor lizards, crocodiles and alligators, turtles, frogs, and newts. During the age of dinosaurs, there were also shorebirds similar to sea gulls and sandpipers. The shorebirds survived also. The reason animals that were in or near the water survived is because it takes a lot of energy to raise the temperature of water just one degree. So, instead of being oven-like, the temperature of the water was cool enough to allow the ancestors of all modern birds to survive. All of the birds we see today are descendants of the shorebirds that survived. From the smallest hummingbird to the ostrich, and everything in between in size and shape, they are all descendants of shorebirds.

    Since the dinosaurs were too big to live underground and since they did not live in or near the water, they were completely wiped out. Humans are lucky, our ancestors were shrew-like mammals and they survived by being underground. There were some mammals that were too big to live underground. They were marsupials living in North America, about the size of raccoons, and they too were wiped out. Scientists find fossil marsupials at Hell Creek, Montana, and they all lived during the age of dinosaurs but not after the end of the Cretaceous. Because they were not living underground, they too were wiped out along with the dinosaurs.  The reason the South American marsupials survived is because their ancestors were marsupial shrews and spent a lot of time underground. The reason Australia has marsupials is because the South American marsupials migrated there via Antarctica, some 20 million years after the dinosaurs became extinct, after they had evolved from the surviving marsupial shrews.

    • Commenter avatarLog in to reply to the answers
  • Anonymous
    1 month ago

    The dinosaurs died of COVID-65,000,000 BC.

    • Commenter avatarLog in to reply to the answers
  • Dixon
    Lv 7
    1 month ago

    Birds are warm blooded and have insulating feathers 

    • ...Show all comments
    • joe1 month agoReport

      and there is no consensus on whether or not all dinosaur were cold blooded. there are some warm blooded fish and reptiles today. tegu (reptile) and opah (fish). mako sharks are also endotherms, able to raise and maintain their body temp. above the surrounding waters

    • Commenter avatarLog in to reply to the answers
  • 1 month ago

    you are on to something there with the beaks vs toothed. but that wouldnt explain why beaked species like triceratops and the Psittacosaurus went extinct. i imagine the true factor was the availability of food. in the initial stages of the extinction, the base of the foodchain fell apart. the plankton and other microbes in the oceans and seas, then the algeas then those that fed on plankton and algaes. then the extinction just went up the foodchain, with predatory animals dying off last. (same on land) the only surviving birds of that time would have been seed and plant eaters, scavengers, and the occasional bird of prey. although it is true that no birds today have teeth, it does not explain the disappearance of the large beaked dinosaurs, if it were not due to the food source. although size did almost definitely play a factor here, with probably the sauropods getting the shortest stick in the bunch. dinosaurs that needed the most food to survive, died off first as the food dwindled. then went the dinosaurs that ate the herbivores, leaving only those that scavenge and eat seeds that can lay dormant for years in some cases (on land, sea birds that fish were probab ly the least effected although the seas suffered most of the death, any fish nerar the surface dead or alive was on the menu. flight was probably the most important factor, because of their ability to travel vast distances over areas that would otherwise be inpassable to land-bound dinosaurs. that would explain why most of the birds today eat seeds or other plants, scavenge, feed off of fish and other birds, and why most fly. as you could imagine, the bird with the smallest belly to fill, would be best off in times of famine and extinction. which is also probably the reason small mammals survived. small mammals tend to share the same food sources as todays birds, eating bugs, plants, seeds, fruits, and  eachother and eggs. in a world that is dying, it is probably some validity to the biggest being the first to go. then once the worst of it was over, the birds that remained spread out and further evolved into what we see today. 

    • Commenter avatarLog in to reply to the answers
Still have questions? Get answers by asking now.