# why didnt any Dinosaurs survive? **URL:** \ **Category:** Factual Questions\ **Created:** [December 28, 2017, 7:24pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479 "2017-12-28T19:24:49Z")\ **Posts on this page:** 20\ **Page:** 4
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 2, 2018, 9:20pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/61 "2018-01-02T21:20:04Z")
> [@DrDeth](#): > > I dont think so, but I am not the expert on what is a “bird”. **Colibri** , what do you think? If small feathered non-avian dinosaurs had survived, I suspect we would call all of them “birds” (or by whatever word we called modern birds), even the ones that didn’t fly. “Animals with feathers” is a pretty natural group when contrasted with those that don’t have them. We had no problem calling ostriches and penguins “birds” even when we didn’t know they belonged to the same clade. After all, we lumped crocodilians, turtles, snakes, and lizards as “reptiles,” even though they are pretty dissimilar and don’t belong to the same clade (at least, if birds are excluded). ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [January 2, 2018, 9:20pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/62 "2018-01-02T21:20:06Z")
> [@Darren\_Garrison](#): > > That reminds me–I have lots of photos where [I’ve stalked](http://s313.photobucket.com/user/darrengarrison/library/carnivorous%20plants?sort=3&start=all&page=1) [your relatives](http://s313.photobucket.com/user/darrengarrison/library/carnivorous%20plants?sort=3&start=all&page=1). Cool! ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [January 2, 2018, 9:31pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/63 "2018-01-02T21:31:10Z")
> [@Colibri](#): > > If small feathered non-avian dinosaurs had survived, I suspect we would call all of them “birds” (or by whatever word we called modern birds), even the ones that didn’t fly. I agree–just like we have to include “egg-laying” as a possible trait of mammals since we still have monotremes around. If the monotremes hadn’t made it, the definition of “mammal” would have been different. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 2, 2018, 9:53pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/64 "2018-01-02T21:53:44Z")
> [@Darren\_Garrison](#): > > I agree–just like we have to include “egg-laying” as a possible trait of mammals since we still have monotremes around. If the monotremes hadn’t made it, the definition of “mammal” would have been different. Cladistically, the definition of a what is known as a [“crown group”](https://en.wikipedia.org/wiki/Crown_group) (all living forms in a group) may be different from what is known as the “stem group” (extinct ancestral group). Modern birds are easy to define on a number of characters. If you go back to the Cretaceous, you have to rely on highly technical characteristics of the skeleton to distinguish them from bird-like dinosaurs. Likewise, for modern mammals we can rely on hair and mammary glands to define them. In fossil forms, they are arbitrarily defined on details of the jaw articulation. ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [January 10, 2018, 4:29pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/65 "2018-01-10T16:29:47Z")
> [@Kedikat](#): > > When a habitat undergoes a drastic change. Some of the species find that to their advantage. Predators and competitors can be wiped out. So some now have a far better habitat. They thrive. Whatever is left of their predators also thrive. As well as those who are somewhat symbiotic with them all. > > It is a choke point. But some can squeeze through, or even take great advantage of it. > > That huge change selected for a narrow band of traits. The big dinosaurs were not terribly efficient creatures. They required a large amount of large vegetation. Which became scarce. Smaller creatures fed on smaller flora and fauna. Which seems to recover and flourish faster after competition is eliminated. Large predators usually hunt larger prey. Which quickly starved out. So predators starved. T Rex would not be good at catching small fast prey. Underlining added to incorrect statement. At least some were according to > [@why did the dinosaurs not evolve back](https://boards.straightdope.com/t/why-did-the-dinosaurs-not-evolve-back/666138/10): > > Plants during the age of the dinosaurs were no larger than the largest modern ones. During the Mesozoic there was a shift in dominance between gymnosperms (conifers and others) and angiosperms (flowering plants), but this happened in the Cretaceous, in the middle of the dinosaurs’ dominance. > > It’s an open question of why dinosaurs got so much larger in the Mesozoic than mammals did during the Tertiary. Changing levels of carbon dioxide (which could have increased plant productivity) or oxygen (which could have permitted greater activity) could have had something to do with it, but these changed throughout the Mesozoic and this can’t be a general explanation. > > Sauropods may have been able to get so big [because of their highly efficient feeding apparatus](http://www.livescience.com/13703-giant-dinosaurs-sauropods-museum-evolution-size.html) and their physiology. Mammals by happenstance have not been able to duplicate this system. The largest carnivores may have evolved to exploit the large sauropods. Dinosaurs in other groups were generally within the range of size reached by the largest mammals, such as [Paraceratherium](http://en.wikipedia.org/wiki/Paraceratherium) (Indricotherium). > > The asteroid strike that killed the dinosaurs did not change Earth’s axis. The most recent ice ages did not start until about 2 million years ago, most likely due to changes in oceanic currents triggered by the closure of the isthmus of Panama. There were no ice caps on Earth at any time during the time dinosaurs were dominant, although there had been [ice ages](http://en.wikipedia.org/wiki/Ice_ages) before dinosaurs evolved. The big sauropods were basically walking fermentation vats. One wonders their impact on climate–they must have emitted huge amounts of methane. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 10, 2018, 4:40pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/66 "2018-01-10T16:40:17Z")
> [@Pleonast](#): > > The big sauropods were basically walking fermentation vats. One wonders their impact on climate–they must have emitted huge amounts of methane. My guess would be that large sauropods would have emitted proportionally less methane than an equal biomass of ungulates. First, the ungulates would be individually much smaller and because of this would have had a higher metabolism and energy requirements, requiring them to process more food. Second, large sauropods may have been passive homeotherms, relying on their vast size to maintain their body temperature, again reducing their relative energy requirements. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [January 10, 2018, 4:49pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/67 "2018-01-10T16:49:19Z")
> [@Colibri](#): > > Second, large sauropods may have been passive homeotherms, relying on their vast size to maintain their body temperature, again reducing their relative energy requirements. Otherwise known as [gigantotherms](https://en.wikipedia.org/wiki/Gigantothermy). ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [January 10, 2018, 6:27pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/68 "2018-01-10T18:27:49Z")
> [@Colibri](#): > > My guess would be that large sauropods would have emitted proportionally less methane than an equal biomass of ungulates. First, the ungulates would be individually much smaller and because of this would have had a higher metabolism and energy requirements, requiring them to process more food. Second, large sauropods may have been passive homeotherms, relying on their vast size to maintain their body temperature, again reducing their relative energy requirements. Doesn’t sauropods’ efficiency mean more biomass of herbivores per biomass of vegetation? And so a greater overall conversion rate of plant carbon into methane compared to ungulates. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 10, 2018, 6:46pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/69 "2018-01-10T18:46:16Z")
> [@Pleonast](#): > > Doesn’t sauropods’ efficiency mean more biomass of herbivores per biomass of vegetation? True. > [@](#): > > And so a greater overall conversion rate of plant carbon into methane compared to ungulates. That doesn’t follow. Greater efficiency means greater conversion of plant carbon into _animal tissue_. Methane is a bacterial waste product and represents an energy loss to the animal. If sauropods used the same fermentation system as ruminants, I think they would produce a similar amount of methane per amount of plant biomass processed, since this is dependent on bacterial processes. (However, kangaroos depend on a different kind of bacteria for fermentation which produces 80% less methane than that of cows. We can’t really know the rate of methane production in sauropods without knowing what system they used.) ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [January 10, 2018, 6:58pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/70 "2018-01-10T18:58:04Z")
> [@Colibri](#): > > That doesn’t follow. Greater efficiency means greater conversion of plant carbon into _animal tissue_. Methane is a bacterial waste product and represents an energy loss to the animal. > > If sauropods used the same fermentation system as ruminants, I think they would produce a similar amount of methane per amount of plant biomass processed, since this is dependent on bacterial processes. (However, kangaroos depend on a different kind of bacteria for fermentation which produces 80% less methane than that of cows. We can’t really know the rate of methane production in sauropods without knowing what system they used.) Okay, that makes sense. But, still, the overall conversion rate of plant carbon into methane is going to be proportional to the total animal biomass. While the amount of methane emitted per ton of sauropod is going to be less than the amount per ton of ungulate, because there’s more tons of sauropod, there’ll be more total methane collectively emitted by the sauropods. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 10, 2018, 7:05pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/71 "2018-01-10T19:05:45Z")
> [@Pleonast](#): > > While the amount of methane emitted per ton of sauropod is going to be less than the amount per ton of ungulate, because there’s more tons of sauropod, there’ll be more total methane collectively emitted by the sauropods. No. The amount of methane depends on the _amount of plant material consumed_, not the amount of animal biomass it supports. 1000 tons of plant material may support 100 tons of sauropods or 50 tons of ungulates, but its still going to produce the same amount of methane when fermented.\* \*Of course, all other things being equal. We don’t know the productivity or digestibility of Mesozoic plants compared to grasses, for example. ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [January 10, 2018, 8:14pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/72 "2018-01-10T20:14:44Z")
> [@Colibri](#): > > No. The amount of methane depends on the _amount of plant material consumed_, not the amount of animal biomass it supports. 1000 tons of plant material may support 100 tons of sauropods or 50 tons of ungulates, but its still going to produce the same amount of methane when fermented.\* > > \*Of course, all other things being equal. We don’t know the productivity or digestibility of Mesozoic plants compared to grasses, for example. Hmm. I see the dependence on the amount of vegetation consumed, but doesn’t the animal consuming it determine how much is converted into animal vs converted into methane vs ejected out the rear end? And there’s also a temporal component. Which goes through the 1000 tons of plants faster: the 100 tons of sauropods or the 50 tons of ungulates? (By the way, thanks for humoring me along this tangent.) ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 10, 2018, 8:30pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/73 "2018-01-10T20:30:32Z")
> [@Pleonast](#): > > Hmm. I see the dependence on the amount of vegetation consumed, but doesn’t the animal consuming it determine how much is converted into animal vs converted into methane vs ejected out the rear end? No. As I’ve already said, the methane is not a product of the animal, it’s a product of the bacteria in its gut. Assuming ungulates and sauropods used the same kinds of bacteria for fermentation (and that’s a big assumption), the same amount of plant material should produce the same amount of methane. > [@](#): > > And there’s also a temporal component. Which goes through the 1000 tons of plants faster: the 100 tons of sauropods or the 50 tons of ungulates? Again, that’s going to be determined by the bacteria rather than the kind of animal. There’s no point in an animal eating faster than the bacteria can ferment what it eats. Think of fermenting alcohol. The rate of production of alcohol is going to depend more on the kind of yeast and amount of sugar rather than the size of the container you’re fermenting it in.\* \*I recognize that the size of the vat could have some effect on the rate of fermentation, but I’m talking about general principles here rather than details. ---
**Author:** ![Bosda\_Di\_Chi\_of\_Tricor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bosda_di_chi_of_tricor/32/16845_2.png) [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)\ **Post date:** [January 10, 2018, 11:16pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/74 "2018-01-10T23:16:46Z")
> [@](#): > > why didnt any Dinosaurs survive? Who says [del]we[/del] they didn’t? 😃 ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [January 11, 2018, 12:16am UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/75 "2018-01-11T00:16:01Z")
[![](https://i.pinimg.com/736x/9b/b8/b0/9bb8b02224e1529a39655526b504bc75--far-side-cartoons-funny-cartoons.jpg) ](https://i.pinimg.com/736x/9b/b8/b0/9bb8b02224e1529a39655526b504bc75--far-side-cartoons-funny-cartoons.jpg) ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [January 11, 2018, 12:57am UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/76 "2018-01-11T00:57:49Z")
> [@Colibri](#): > > If small feathered non-avian dinosaurs had survived, I suspect we would call all of them “birds” (or by whatever word we called modern birds), even the ones that didn’t fly. “Animals with feathers” is a pretty natural group when contrasted with those that don’t have them. We had no problem calling ostriches and penguins “birds” even when we didn’t know they belonged to the same clade. True, but there is still a fair question to ask why _these_ feathered dinosaurs survived and _those_ feathered dinosaurs didn’t, regardless of how those divisions occurred. In other words, we could still sensibly ask the same question, we just might have different answers because the dividing lines are in different places. We’re basically looking at the traits that differed and then trying to back-explain why those differences had different outcomes. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [January 11, 2018, 1:02pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/77 "2018-01-11T13:02:30Z")
> [@Irishman](#): > > True, but there is still a fair question to ask why _these_ feathered dinosaurs survived and _those_ feathered dinosaurs didn’t, regardless of how those divisions occurred. And the answer may be “no particular reason.” A viable population of species a might have just happened to be in a sufficiently sheltered spot after the impact and species _b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y,_ and _z_ didn’t. And it could have just as easily have been one of the other species, or have been none at all. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 11, 2018, 2:06pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/78 "2018-01-11T14:06:09Z")
> [@Darren\_Garrison](#): > > And the answer may be “no particular reason.” A viable population of species a might have just happened to be in a sufficiently sheltered spot after the impact and species _b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y,_ and _z_ didn’t. And it could have just as easily have been one of the other species, or have been none at all. Right. It’s easy to explain why certain groups were all killed off - basically everything large - than which groups survived among the rest. Some birds survived because they were small and could fly. But it’s important to emphasize that _nearly all birds became extinct as well_, as well as all other small flying vertebrates. Being small and capable of flight didn’t save the pterosaurs or enantiornitine birds. As mentioned above, only four clades of birds appear to have survived the extinction event, which means _as few as four species may have survived_. (It was probably somewhat more, but quite possibly more than 95% of bird species existing at the time were killed off.) And evidence suggests that [93% of all mammals](https://www.theregister.co.uk/2016/06/20/mammals_nearly_wiped_out_in_asteroid_impact/) were killed off. Even among the groups that survived which species did so was largely a lottery. ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [January 11, 2018, 5:25pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/79 "2018-01-11T17:25:25Z")
> [@Colibri](#): > > Even among the groups that survived which species did so was largely a lottery. And we get excited when the Powerball goes to $500M. :smack: ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 11, 2018, 10:23pm UTC](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479/80 "2018-01-11T22:23:35Z")
> [@](#): > > Quoth **Colibri** : > > As mentioned above, only four clades of birds appear to have survived the extinction event, which means as few as four species may have survived. And even among those few lucky species (however many of them there were), probably most of the individuals died off, too. It could be that, of all of the myriad birds of thousands of different species who could have been over the lake (and away from the fires) at the moment, it just happened to be those particular ones who actually were. [Previous page](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479.md?page=3) [Next page](https://boards.straightdope.com/t/why-didnt-any-dinosaurs-survive/805479.md?page=5)