[HN Gopher] Why birds survived and dinosaurs went extinct after ...
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Why birds survived and dinosaurs went extinct after an asteroid hit
earth (2020)
Author : hwayne
Score : 69 points
Date : 2024-04-11 17:55 UTC (5 hours ago)
(HTM) web link (www.smithsonianmag.com)
(TXT) w3m dump (www.smithsonianmag.com)
| dang wrote:
| Discussed a bit at the time (of the article):
|
| _Why Birds Survived, and Dinosaurs Went Extinct, After an
| Asteroid Hit Earth_ -
| https://news.ycombinator.com/item?id=24488527 - Sept 2020 (3
| comments)
| eslaught wrote:
| Looks like no one answered this question from the last time
| around:
|
| https://news.ycombinator.com/item?id=24492646
| mikeyouse wrote:
| _Q: Anyway, my problem with the argument is that some mammals
| obviously survived. Why? We had worse lungs, roughly the same
| amount of protection against the cold as many small
| dinosaurs... so what gives?_
|
| A possible answer from this article
| (https://www.scientificamerican.com/article/how-mammals-
| conqu...)
|
| _The earliest Paleocene scene is dire. There is a fossil
| locality in Montana dated to approximately 25,000 years after
| the asteroid hit, called the Z-Line Quarry. It reeks of
| death. Almost all the mammals that flourished in the region
| in the Cretaceous are gone; only seven species remain.
| Several other fossil sites divulge what was happening over
| the next 100,000 to 200,000 years. If you pool together all
| mammals from this time, there are 23 species. Only one of
| these is a metatherian; these marsupial ancestors, once so
| abundant in the Cretaceous, were nearly extinguished. All
| told, if you consider the entire Montana fossil record, along
| with other data from across western North America, the
| statistics are grim. A paltry 7 percent of mammals survived
| the carnage. Imagine a game of asteroid roulette: a gun, with
| 10 chambers, nine of which hold a bullet. Even those odds of
| survival are slightly better than what our ancestors faced in
| the brave new world of the Paleocene._
|
| _This bleak state of affairs raises a question: What allowed
| some mammals to endure? The answer became apparent when
| Wilson Mantilla looked at the victims and survivors. The
| survivors were smaller than most of the Cretaceous mammals,
| and their teeth indicate they had generalist, omnivorous
| diets. The victims, on the other hand, were larger, with more
| specialized carnivorous or herbivorous diets. They were
| supremely adapted to the latest Cretaceous world, but when
| the asteroid unleashed disaster, their adaptations became
| hardships. The smaller generalists, in contrast, were better
| able to eat whatever was on offer in the postimpact chaos,
| and they could have more easily hunkered down to wait out the
| worst of the bedlam._
|
| _As ecosystems recovered in the earliest Paleocene, many of
| the mammals that started to multiply were eutherians, the
| placental antecedents that were once bit players in the
| Cretaceous. Their tiny bodies, flexible diets, and perhaps
| faster ways of growing and reproducing allowed them to
| commandeer open niches and start building new food webs.
| Around 100,000 years postasteroid a new eutherian appeared in
| Montana and swiftly became common. Purgatorius, with gentle
| molar cusps for eating fruits and highly mobile ankles for
| clinging and climbing in the trees, was an early member of
| the primate line. It, or perhaps another closely related
| eutherian, was our ancestor._
| nonameiguess wrote:
| In addition to the more detailed quoted answer, I believe the
| surviving mammals mostly lived underground, shielding them
| from many of the worst effects happening on surface world.
| Many were blind anyway and did well in the darkness of the
| clouded surface. Their predators all died off. The biggest
| remaining threat would have been lack of food, but as the
| other answer states, they had more flexible diets than
| dinosaurs and mammals that did not survive.
| mistrial9 wrote:
| the video commercials on that site make the news item unreadable
| MeImCounting wrote:
| I just Xed out the "Looks like youre blocking ads" dialogue and
| was able to read the article fine.
| spacecadet wrote:
| Good shout, drives me crazy- The Smithsonian cant run a site
| without ads???
|
| "The Smithsonian's annual budget is around $1.25 billion, with
| two-thirds coming from annual federal appropriations."
| hwayne wrote:
| After reading this, my main question changed from "why did birds
| survive" to "why did crocodiles survive".
| pfdietz wrote:
| Low metabolism and they live in fresh water, shielding them
| from the heating impulse after the impact. Fresh water
| ecosystems fed by detritus from dead plants could survive the
| post-impact period of darkness as well.
| holoduke wrote:
| Didn't crocodiles evolved two time separately?
| IncreasePosts wrote:
| No? Alligators, ghalials, caimans, and crocs all share a
| common ancestor ~120MYA that was very similar to all of those
| species.
| CatWChainsaw wrote:
| "Gee, I don't know. Maybe deep down I'm afraid of any apex
| predator that lived through the K-T extinction. Physically
| unchanged for a hundred million years, because it's the perfect
| killing machine. A half ton of cold-blooded fury, the bite
| force of 20,000 Newtons, and stomach acid so strong it can
| dissolve bones and hoofs."
|
| ( _Archer_ )
| pvg wrote:
| Don't have an answer other than to say their lineage is sturdy
| enough to have pulled it off twice - crocodylomorpha were just
| about the only survivors of their giant and dominant clade in
| the end-Triassic extinction and, of course, they made it past
| the asteroid 135 million years later.
| prmoustache wrote:
| I would have thought about fishing before eating seeds tbh.
| jjk166 wrote:
| In the aftermath of the extinction food webs collapsed as
| photosynthesis basically shut down for several years. Birds
| could find and eat seeds buried before the extinction, which
| along with their ability to fly long distances meant they could
| find enough calories to survive in environments that weren't
| producing any.
| neonate wrote:
| https://web.archive.org/web/20240124195601/https://www.smith...
|
| https://archive.ph/c0hHJ
| ado__dev wrote:
| The birds had wings, so they could just fly away. /s
| taylodl wrote:
| Imagine a T. Rex looking up at the sky at _huge_ flocks of
| birds leaving! Good for them their peanut-sized brain had no
| awareness of what was going on!
| empath-nirvana wrote:
| https://en.wikipedia.org/wiki/Deccan_Traps
|
| This happened roughly contemporaneously to the asteroid strike.
| Retric wrote:
| And at the opposite side of the earth, suggesting it is a
| direct result of the impact.
| dboreham wrote:
| We're trying to infer a query here: SELECT species FROM animals
| WHERE habitat IN [protected_from_burning_sky] AND diet IN
| [non_photosynthesis_dependant_foods]
| RajT88 wrote:
| Birds _are_ dinosaurs:
|
| https://www.birdlife.org/news/2021/12/21/its-official-birds-...
|
| A fact I'm reminded of when I spook a stork/heron/crane when I'm
| walking my dog along the river near me. They make a crazy
| dinosaur sound, and in flight even resemble somewhat the classic
| illustrations of Pterosaurs.
|
| Bonus link, the common ancestor of both birds and crocodiles:
|
| https://en.wikipedia.org/wiki/Archosaur
| s0rce wrote:
| I think that chickens look like dinosaurs.
| RajT88 wrote:
| Some mad scientist a while back wanted to devolve Chickens
| into (basically) velociraptors. This was decades back, but I
| could see what he's talking about. Apparently with CRISPR now
| some scientists are doing similar things at small scales.
| elevaet wrote:
| > They make a crazy dinosaur sound
|
| Do they? Or maybe we base out ideas of what dinosaurs might
| have sounded like on birds like these... ;)
| magicalist wrote:
| > _Birds are dinosaurs_
|
| But not all dinosaurs were birds, which is what the article is
| about.
|
| > _and in flight even resemble somewhat the classic
| illustrations of Pterosaurs_
|
| Pterosaurs weren't dinosaurs. Muphry's law? :)
| RajT88 wrote:
| Quite so. TIL that Pterosauromorpha and Dinosauromorpha are
| different clades underneath Ornithodira.
|
| Next to dinosaurs on the tree of life, but not dinosaurs.
| MilStdJunkie wrote:
| I'm really sorry to be that guy, but just FYI, the pterosaurids
| weren't dinosaurs or dinosauroporphs, and were on a pretty
| independent evolutionary lineage. It's astonishing how many
| times vertebrates evolved flight _independently_. It 's a sharp
| reminder of how long dozens or hundreds of millions of years
| are.
|
| Having said that, the "long necked stabby stabby from
| elsewhere" was a theme with the dinosaurs proper. Some have
| theorized that this was the hunting mode of the giant
| _Spinosaurus_.
|
| You're right on the money with the dinosaurs=birds though
| though. Paleo guys even have started saying "non-avian
| dinosaurs" to reference the kpg "classic" dinosauromorpha,
| because the lineages are so intertwined. Archaeopteryx, to take
| one example, might not have been a bird, exactly? Birds might
| be even more intertwined than that, with separate bird lineages
| branching out at different times. The takeaway from the big
| extinctions is that you need to be less than fifty kilos and
| preferably able to dive or burrow very very deep. And be lucky,
| of course. Everything standing around within a few thousand
| miles of Cancun 65mya was probably screwed no matter how cool
| it was.
| RajT88 wrote:
| > I'm really sorry to be that guy
|
| No worries! Someone already beat you to the punch anyways. ;)
| m463 wrote:
| I thought at some point they found dinosaurs might have had
| (colorful) feathers that might not have been represented by
| fossils.
|
| hmmm, maybe I don't know anything
|
| https://en.wikipedia.org/wiki/Feathered_dinosaur
|
| https://en.wikipedia.org/wiki/List_of_non-avian_dinosaur_spe...
|
| https://en.wikipedia.org/wiki/Origin_of_birds
| BurningFrog wrote:
| > _They make a crazy dinosaur sound_
|
| Found the time traveler!!
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