Why did birds, of all the dinosaurs, survive the KT event?

[foodchain]

This sounds like a general statement -- that there

 

If you can understand with objective clarity while aves made it, go ahead first of all. Of course the entire class did not make it, not every specie that lead to modern humans made it, but we don’t have our own entire specification taxonomically speaking, and I would strongly suggest there exists a fine reason for why taxonomy exists.

 

You can look at bacteria and say overall that some specie of bacteria all on its own might survive or be able to persist, but I don’t know if birds would be able to persist for instance if birds were to only specie, which was simply to back up my point that you might have to look at why birds survived in a broader sense then just an individual specie all by itself in some void. That point was to go on about my point in general about looking at natural history as a whole rather then as individual unconnected pieces to attempt to learn why birds were able to persist through such a massive extinction event. I mean what are the survival values to what lived, more so with birds, did they build less accessible nests for one example of a question? I am not trying to speak specifically because I don’t posses the understanding of Aves in general to do such, if you do feel free to go on about it.

 

My point in general about a case to case basis is important in a few respects. Attempting to stay healthy and fit for say one particular specie may not be conducted the same way as for another specie. To say birds made it because of a bird trait is fine, but that probably does not attack the issue at enough detail.

[SkepticLance]

My country, New Zealand, is actually a more recent and very similar though local case. The fossil record shows that NZ had a broad population of dinosaurs. However, before humans arrived 800 years ago, there were no large terrestrial land reptiles or mammals. There was, instead, a massive population of birds that had evolved to exploit the normal range of niches that mammals and reptiles enjoy.

 

The reason for this appears to be that, during the Miocene, the entire country went underwater for a period. This would have wiped out all land animals. After surfacing again, a wave of invaders took over. This included birds that could fly there, and small reptiles that could survive months without food or water, and drift on small clumps of debris. The birds became king, evolving into flightless forms up to 3 metres high, and into a wide range of tiny forms also. The major predator was the giant NZ eagle - at the time the largest eagle on Earth. 11 species of flightless moa became the grazers, ranging from 3 metres tall to turkey size. The only mammals were two tiny species of bat, and pinnipeds and cetaceans.

 

Bearing in mind what happened in NZ, is it possible that much of the Earth above water was essentially sterilised by the KT event, similar to NZ going underwater, leaving pockets in isolated areas? Only the most mobile were able to migrate to repopulate the once sterile planet, leaving the dinosaurs to die.

[lucaspa]

touche, ya i didn't realize that she meant pioneer as in just 2 individuals. you could probably do it with just one male and multiple females but ya i agree just 2 people is not very likely to work.

 

I think we have a disconnect on why a founder event will fail. When you say "one male and multiple females" you make it seem like you need genetic variability so you avoid inbreeding. Nope. You CAN do it with one male and one female. The problem isn't genetic variability to avoid inbreeding. No the problem is two fold:

1. Whether the 2 individuals are able to survive where they end up. IOW, you can have lots of founder events, but most of the time the environment is just TOO different and the individuals can't survive there at all.

2. Accidents in the first couple of generations. In this scenario the 2 animals can survive in the new environment but accidents (chance) play a role. Say the G0 parents have 1 child -- a male -- and the mother slips, falls down a slope, and dies. The founder event has failed.

 

I understand that it happens, and my post was not intended to suggest this is not the case. I did specify "higher organisms", and I do not consider drosophila to be particularly well suited to that category.

Others may disagree I suppose, so this is clarification for those who do: the order of complexity which I am considering in the likelihood of a founder event is equal to or greater than the order of complexity for the groups we have been discussing throughout the thread (birds etc).

 

I think your distinction is artificial. You are basing "complexity" only on the presence of a spinal column. So what you are saying is that founder events are rare in the Phylum Vertebrates

 

http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=15813781&dopt=Abstract

http://books.nap.edu/openbook.php?record_id=10865&page=14

http://www.mun.ca/serg/genet43380.pdf look at the references in this one.

 

http://links.jstor.org/sici?sici=0014-3820(199404)48:2%3C490:MOSIBA%3E2.0.CO;2-W A study by Lynch cited here indicates that 15% of the speciation in the vertebrates studied were "peripheral isolates", which is equivalent to founder events we are talking about. They use "vicariance" to refer to allopatric speciation by geographical barriers.

 

Also remember that Darwin's finches are supposed to have resulted from founder events.

 

Let me dig out my typewriter. By golly, Nature won't know what hit them!

 

You might want to correspond with the guy whose website I cited. I'm thinking he would be your best source as the to lifestyle of the neornithine species that made it thru the KT.

 

I don’t know if birds would be able to persist for instance if birds were to only specie,

 

Oh yes! Foodchain, the only biological reality is species. "Birds" are really a group of species. It doesn't have any objective reality, but represents human taxonomy.

 

Also, run this backwards: EVERY taxonomic category above species started with a single species! That's how it MUST be with evolution: "descent with modification" and having A common ancestor. I'd suggest you look at the diagram in Origin of Species (there's only 1, you can't miss it).

 

Look at the ancestry of H. sapiens. About 7 million years ago there was THE common ancestor of chimps and humans. One species. Call it A. Now, there are 3 possibilities:

1. A gave rise to species C and C went on to chimps while A went to hominids.

2. A gave raise to species H, and H went on to hominids while A went to chimps.

3. A split to 2 new species C and H. Now you have 3 species. A goes extinct. C goes to chimps and H goes to hominids.

 

But any way you slice it, all the species in the genus Homo started from a single species.

 

So yes, a single species of Aves could, thru cladogenesis (splitting of an original species to 2 or more), generate all the species we see in Aves today.

 

which was simply to back up my point that you might have to look at why birds survived in a broader sense then just an individual specie all by itself in some void.

 

No, each species must survive. If you have many species in a group, then you try to look for commonalities between the species. Do the species have something in common that caused the group to survive while other groups did not?

 

That point was to go on about my point in general about looking at natural history as a whole rather then as individual unconnected pieces to attempt to learn why birds were able to persist through such a massive extinction event. ...

My point in general about a case to case basis is important in a few respects. Attempting to stay healthy and fit for say one particular specie may not be conducted the same way as for another specie. To say birds made it because of a bird trait is fine, but that probably does not attack the issue at enough detail.

 

This is where you confuse us, because these 2 points contradict! First you are saying that we must look for a "bird trait" because we must consider birds "as a whole". Then you turn around and say that survival may be due to traits specific to each species and NOT a "bird trait" because it is not shared by all birds! Can you not see the contradiction?

 

What I am saying is that only a minority of bird species made it thru the extinction. So ... the conclusion is that we are not looking at traits shared by all birds -- otherwise most of the species would have survived. Instead, we are looking for a much narrower group of species within the Class Birds. And, thanks to Sayonara, we may have found it: seabirds that burrow in the sand of the beach. This adaptation of making burrows in sand is going to be very limited among bird species -- only a few species will have it. Some of those species will be closely related -- same genus or family. Other species may have evolved burrowing independently and belong to a different order.

 

You can also look at it this way: the species did not survive because they were birds. They survived because they burrowed. Being a bird or mammal or reptile was incidental and not related.

 

Bearing in mind what happened in NZ, is it possible that much of the Earth above water was essentially sterilised by the KT event, similar to NZ going underwater, leaving pockets in isolated areas? Only the most mobile were able to migrate to repopulate the once sterile planet, leaving the dinosaurs to die.

 

SkepticLance, I see one major problem with that: dinosaurs were among the most mobile! Remember, turtles survived the KT event. I have this picture of a turtle and hadrosaur migrating and the turtle leaving the hadrosaur in the dust! Yeah, right!

 

From the evidence, most of the land surface was not "sterilized" by the impact itself. OK, the fireball would have extended up to 5,000 km radius, which covers most of North and South America. Eurasia tho, is unaffected by the fireball. What they have to contend with is the global climate disruption and nuclear winter. http://members.optusnet.com.au/mpaineau/paine_bioastronomy02.pdf

 

And we know there were dinos in Eurasia at the end of the Cretaceous. Again, which species is more likely to be able to migrate to the Americas? Turtles or hadrosaurs?

[SkepticLance]

lucaspa said :

 

SkepticLance, I see one major problem with that: dinosaurs were among the most mobile!

 

One question. Do you know what marine dinosaurs survived to the end of the Cretaceous? Since fish survived, it would seem that totally marine animals would have an advantage.

 

The New Zealand case, though, has some clear commonalities with the KT event. It may be worth thinking about.

[foodchain]

To Lucaspa:

 

Taxonomy may be a human made tool, but its goal is to reflect natural kinds and the relationship they hold. Its a product of evolution basically. Of course modern molecular techniques will have a sway and there are species of taxonomists really, such as being a cladist for instance. This of course does not denote the importance to taxonomy or the use of the tool. Its pretty much comparable to say a periodic table. For instance if I was to be giving an assignment to find per say species X that is related to species Y, and all I am giving is species Y, do you think looking into taxa or systematics of Y would help at all?

[lucaspa]

Taxonomy may be a human made tool, but its goal is to reflect natural kinds and the relationship they hold. Its a product of evolution basically.

 

Let's get back to what I actually said:

1. The only biological reality is species. These are real populations.

2. Higher taxa are not "real", but are rather simply groups of species.

 

So, when you are looking at what survives an extinction, or what diversifies, you are looking at species. Not "class". The Class of Aves did not survive the KT extinction. Rather, species that humans put in the Class Aves did.

 

We can look at morphology/physiology/behavior that these species had in common, but saying "why did birds survive but dinos did not" does not capture the reality. Not ALL species of birds survived. Instead, the way to correctly phrase that question is "Why did a few species of birds survive but all species of dinos went extinct?"

 

What you have done in your post is make an irrelevant digression into taxonomy.

 

FYI, our current classification system was made by a creationist. Yes, Linneaus was a creationist. The classification supports evolution because the classification is a nested heirarchy, and nested hierarchies are a product of descent with modification.

 

lucaspa said :

 

One question. Do you know what marine dinosaurs survived to the end of the Cretaceous? Since fish survived, it would seem that totally marine animals would have an advantage.

 

http://www.physics.vanderbilt.edu/astrocourses/AST101/readings/kt_extinction.html

"Icthyosaurs: These fish-lizards died out 30 million years before the K/T extinction.

 

Plesiosaurs: These creatures had decreased from 6 families to only 2, at the approximate time of the K/T extinction.

Vertebrate species: More than 50% of vertebrate species survived across the K/T boundary, in the fossil record of what is now the western United States. Not including very rare fossil species, for which often only a single fossil is known, 70% survived. The extinctions were concentrated in only five of 12 taxa of vertebrates. Hit hard were sharks & relatives (less than 20% survival), bird-hipped dinosaurs (0% survival), reptile-hipped dinosaurs (0% survival, except birds), lizards (less than 30% survival) and marsupials (less than 10% survival). Completely unaffected were frogs & salamanders, champsosaurs, and placentals; barely affected were turtles (85% survival), crocodilians (80% survival), bony fishes (70% survival) and multituberculates (50% survival). ...

 

Mosasaurs: These giant marine reptiles (up to 17-m in length) lived from about 90-65 MY ago. They appear to have been diversifying and undergoing a mass radiation shortly before the K/T event, with most of this occurring from 75-65 MY ago. They apparently went extinct abruptly at the K/T boundary. "

 

The New Zealand case, though, has some clear commonalities with the KT event. It may be worth thinking about.

 

New Zealand seems to be a typical example of biogeographic distribution of an isolated island. Other examples we have are volcanic islands that are newly formed -- the Galapagos and Cape St. Verde islands. Therefore it is more related to that than the KT extinction event.

[bombus]

Please provide examples.

 

 

 

ROFL! Bombus, please don't display your ignorance quite so openly. An Associate Professor is a "real" professor. The ranks go: Assistant Professor, Associate Professor, Professor. ALL are "professors". In the USA Assistant Professor is a rank before you have tenure. When you are promoted to tenure you get the rank of Associate Professor. When you have served on an NIH Study Section, an editorial board of a journal, and a few other things, you are promoted to Professor. The chairman of my department is ranked Associate Professor!

 

You are easily amused

 

 

 

Now you are just trying to trot out the Argument from Authority.

Often a very good one

 

 

 

She isn't going on meeting him personally, but what he wrote in the book! The issue is still whether the book is as Dr. Walker portrayed it (and yes, you should use her professional title). So far, you haven't given us any evidence to the contrary.

 

I did start doing a critique of her review, but realised it would take too much of my precious time. Why don't you just borrow the book from a library and judge for yourself? You won't have to take my word for it then.

 

I firmly believe he is on to something BIG.

[lucaspa]

You are easily amused

 

And you commonly make misstatements of fact. You did so when you tried to denigrate the reviewer by saying an Associate Professor was not a "real" professor.

 

Often a very good one

 

It's a logical fallacy.

 

Lucaspa: The issue is still whether the book is as Dr. Walker portrayed it (and yes, you should use her professional title). So far, you haven't given us any evidence to the contrary.

 

bombus: I did start doing a critique of her review, but realised it would take too much of my precious time.

 

Translation: you still won't provide us with any evidence.

 

I firmly believe he is on to something BIG.

 

Since you stated it as a belief and not science, fine. You can believe what you like. Data will tell us whether your belief corresponds to reality, as it always does in science.

[bombus]

And you commonly make misstatements of fact. You did so when you tried to denigrate the reviewer by saying an Associate Professor was not a "real" professor.

 

An associate professor (nor an assistant) is NOT a full Professor, as you pointed out.

 

Translation: you still won't provide us with any evidence.

 

I have a life. Just borrow the book and you won't have to rely on my mis-statements of facts.

 

 

Since you stated it as a belief and not science, fine. You can believe what you like. Data will tell us whether your belief corresponds to reality, as it always does in science.

 

Well, I am fine with that. I have seen the data. When you see the data you can decide for yourself. I am not going to spend half my life putting it up here on this forum though. That's what libraries are for:-)

[lucaspa]

An associate professor (nor an assistant) is NOT a full Professor, as you pointed out.

 

But they are REAL professors. It's a matter of naming positions, not deciding credibility.

 

I have a life. Just borrow the book and you won't have to rely on my mis-statements of facts.

 

You have time to write all these posts. Surely you have time to include some specifics from the book.

 

I have seen the data. When you see the data you can decide for yourself. I am not going to spend half my life putting it up here on this forum though. That's what libraries are for

 

You don't have to put all of it up. Just a few examples to back your claims. I find it interesting that you won't even do ONE example.

[mrbrklyn]

That last sentence makes no sense. Why would you have a "tailing off" for 10 million years before the meteor hit? If it was a catastrophic kill on a robust lineage, you should see the same populations up until the moment the meteor hits.

 

So, can you please point us to your sources? We seem to have contradictory data -- decline in numbers of individuals and species before the KT implact and no decline. We need to look at the original papers to resolve this.

 

 

The statement about the statistical likelihood of fossil survival (or any other process) after the sudden extinction (or ending) is statistically valid and covered in any elementary stats text. Furthermore, the event itself would have destroyed much of the fossil evidence since it seems likely that a world-wide fireball incinerated most of the biosphere .

[Chaotician]

I tend to favor Bombus' answer. I think it would be a matter of the amount of food needed per animal combined with ability to withstand the cold of the winter. Mammals, turtles, and some reptiles burrow, thus insulating themselves against the winter. The feathered dinos were 1) larger and 2) carnivores. So they were more susceptible to the cold and their food supply died.

 

As Bombus noted, many birds eat seeds or carrion. Even if the plants died, the seeds would still be available. The smaller birds would not need so much food and would have less body area to lose heat.

 

Remember that several genera of birds also went extinct at the K-T boundary. BTW, birds are descended from dinos, but the class Aves was well established by the time the K-T event occurred.

 

I have not seen a paper discussing the reasons the birds survived. Not surprising, since there is still debate as to the exact reason the dinos went extinct. Data indicates that the number of dino species was in a steep decline for at least 10 million years prior to the meteor impact. Robert Bakker, for one, doesn't think the meteor was the primary cause of dino extinction, but merely provided the icing on the cake. His position is controversial, but respected.

 

that makes sense, the meteor strike must have had the final nail in the coffin of an already over-extended species in full decline. the question is do we see the same thing today with humans. a mass extinction event is probably in the works right now and i dont think humans will make it for much longer

[Moontanman]

Wow, thanks for resurrecting this thread but I've read through it several times and talk about ignoring the real issue!

 

Some facts

 

There was no world wide fireball, probably lots of fires set around the glob from reentry of debris but no world wide fireball.

 

There were no marine dinosaurs, none, period.... All marine top predators were impacted severely, only sea turtles survived among the marine reptiles. Quite possibly because they were the only marine reptiles that ate plants and jellyfish which as seen in todays oceans seem to do well in environmental upheavals.

 

 

Not a real image of course but it illustrates the problem well. Jelly fish are becoming a real problem around the world in waters both stressed by environmental pollution and removal of predators of jelly fish like sea turtles.

 

http://www.thetechherald.com/article.php/200832/1636/Increase-in-world-jellyfish-population-bad-sign-for-planet-scientists

 

Environmental stress always impacts top predators/consumers more than lower level creatures in the food chain, dinosaurs were the epitome of top predators/consumers.

 

In a blizzard with no shelter a shrew would die far quicker than an elephant and an elephant or elephant sized creature could live far longer than a shrew sized animal even with the same metabolism which shrews obviously do not have. A shrew dies with in hours of not feeding, and elephant lives for days maybe weeks with no food and can recover when food becomes available, the shrews are all dead... Birds die in the winter of freezing quite often, some times falling from the sky in large numbers, small birds are more vulnerable than large birds...

 

 

An amazing number and diverse species of animals survived the K/T boundary (many plants didn't make it either) All most all can be said to have been preadapted for survival, burrowing birds, hibernating reptiles and mammals, hibernation or estivation would seem to be key in the survival of species across the KT boundary.

 

http://en.wikipedia.org/wiki/Estivation

 

http://en.wikipedia.org/wiki/Hibernation

[jess]

This it just my opinion I believe that there was no comet. I believe they all evolved into what they are today but very slowly. I believe we still are evolving and that this global warming stuff is just the earth changing because once upon a time there was only 1 contenant and most of it was ice

I think we should be breathing more co2 to feed the trees.

[Moontanman]

This it just my opinion I believe that there was no comet. I believe they all evolved into what they are today but very slowly.

 

 

Do you have any evidence to support this idea? All the evidence i am aware of negates this idea completely.

 

 

I believe we still are evolving and that this global warming stuff is just the earth changing because once upon a time there was only 1 contenant and most of it was ice

 

I think we should be breathing more co2 to feed the trees.

 

 

Again, I ask for any thing that supports this idea.

Edited July 9, 2012 by Moontanman

[jess]

Well There was a big earth quack which would of made the volcano's erupt from the plates moving which would of preserved the bones and made fossils killing most dinosaurs mainly the bigger ones also the climate changed because Australia was ice land once. whales had legs once and that's were all the weird relatives come in and if every thing died out then how did life come back to earth.

 

 

 

Mars was probably another life planet that suffered the same stuff we are. mars shows traces of water by the cliffs and rocks.

[Moontanman]

Well There was a big earth quack which would of made the volcano's erupt from the plates moving which would of preserved the bones and made fossils killing most dinosaurs mainly the bigger ones also the climate changed because Australia was ice land once. whales had legs once and that's were all the weird relatives come in and if every thing died out then how did life come back to earth.

 

No one has said everything died out jess, many animals died, many species did and among dinosaurs only the avian dinosaurs survived. There were enough mammals, reptiles and other animals who survived to repopulate and evolved into the animals we see today. Aquatic animals, land animals, and plants both microscopic and macroscopic were affected abruptly at the K/T boundary.

 

Mars was probably another life planet that suffered the same stuff we are. mars shows traces of water by the cliffs and rocks.

 

This is quite a claim, I'm not sure i understand what you mean...

[jess]

http://zuserver2.star.ucl.ac.uk/~idh/apod/image/0503/marscliffs_express.jpg

 

 

 

scientists believe that the only way those cliff's could have formed was by water and are still looking for water as it might be a planet we might be able to inhabit.

[Moontanman]

http://zuserver2.star.ucl.ac.uk/~idh/apod/image/0503/marscliffs_express.jpg

 

 

 

scientists believe that the only way those cliff's could have formed was by water and are still looking for water as it might be a planet we might be able to inhabit.

 

I still don't see how you can connect that with the extinction of the dinosaurs.

[lucaspa]

The statement about the statistical likelihood of fossil survival (or any other process) after the sudden extinction (or ending) is statistically valid and covered in any elementary stats text. Furthermore, the event itself would have destroyed much of the fossil evidence since it seems likely that a world-wide fireball incinerated most of the biosphere .

 

We seem to be talking about 2 different things. The layers of sediment are undisturbed up until the layer at the KT boundary. Above that boundary there are no dino fossils.

 

However, below that boundary several paleontologists have done biostratigraphic studies on the numbers of dinos of various species. This is a common practice in paleontology. What they found is that the absolute numbers of individuals in dino species was declining for up to 10 million years before the impact. What is more, the number of species was also declining as several species went extinct before the impact.

 

Most commentary of the impact has a fireball that incinerated the biosphere in most of what is now North and South America. However, the biosphere in Asia was not touched by the fireball. Instead, there would have been global winter from all the dust, smoke, and ash kicked up by the impact.

---

Merged post follows:

Consecutive posts merged

This it just my opinion I believe that there was no comet.

 

Actually, the KT event was a meteor. There is considerable evidence -- including the crator at Chixulub in Mexico -- to refute this claim.

 

I believe they all evolved into what they are today but very slowly.

 

Again, nearly every genera of birds went extinct at the KT boundary. The birds we have today are the descendents of the few surviving genera.

 

I believe we still are evolving and that this global warming stuff is just the earth changing because once upon a time there was only 1 contenant and most of it was ice

 

This is very off topic. Way back a billion years ago the earch was indeed covered by ice. However, there have been several continents now for over 200 million years and we have had much colder climates no more than 12,000 years ago. Are you thinking of the Ice Age?

 

I think we should be breathing more co2 to feed the trees.

 

You put out more CO2 in your car a day than you can ever breathe out of your body. The idea of putting out more CO2 to feed the trees doesn't work. There is only so much CO2 that each tree can absorb. If we put out more CO2 than that, then it goes into the atmosphere and acts as an agent to trap heat on the planet -- which is what is causing global warming. It is too much CO2 already that is causing global warming.

 

But again, that is off topic, so let's stick to why the birds survived the KT extinction, OK?

---

Merged post follows:

Consecutive posts merged

In a blizzard with no shelter a shrew would die far quicker than an elephant and an elephant or elephant sized creature could live far longer than a shrew sized animal even with the same metabolism which shrews obviously do not have. A shrew dies with in hours of not feeding, and elephant lives for days maybe weeks with no food and can recover when food becomes available, the shrews are all dead... Birds die in the winter of freezing quite often, some times falling from the sky in large numbers, small birds are more vulnerable than large birds...

 

We need to look at this more carefully. Obviously, shrews did survive the KT event, as did other small mammals. Instead, it was the larger dinos that died.

 

Your premise seems to be "no shelter". But smaller animals have a much better chance of finding shelter. They are smaller and the shelter is thus smaller. And, altho they eat more per body weight, the absolute amount of food they need per day is much smaller. Compare what an elephant and shrew needs per day. An elephant needs tons, a shrew an ounce.

 

So no, in the type of global winter envisioned after the KT impact, the larger animals are more vulnerable: less likely to find shelter, more surface area to radiate body heat, more food required. That is why the larger species died out at the KT and the smaller species survived.

 

An amazing number and diverse species of animals survived the K/T boundary (many plants didn't make it either)

 

A very small number of species survived; that's why it is a mass extinction. I would agree that it seems the burrowers had an advantage; that seems to be what happened with birds. Also species that could go into hibernation -- such as some species of turtles -- also had an advantage. However, estivation would not have helped since that takes heat, and the events after the KT were global winter. Not the right signals to put the animal into estivation.

 

BTW, it's not really "pre-adaption" as evolutionists use the term. It's luck.

Edited July 3, 2010 by lucaspa
Consecutive posts merged.

[Moontanman]

However, below that boundary several paleontologists have done biostratigraphic studies on the numbers of dinos of various species. This is a common practice in paleontology. What they found is that the absolute numbers of individuals in dino species was declining for up to 10 million years before the impact. What is more, the number of species was also declining as several species went extinct before the impact.

 

This is disputed, the main stream school of thought says this is sampling bias, not a true indication of declining dinosaurs...

 

Most commentary of the impact has a fireball that incinerated the biosphere in most of what is now North and South America. However, the biosphere in Asia was not touched by the fireball. Instead, there would have been global winter from all the dust, smoke, and ash kicked up by the impact.

 

There were almost certainly world wide fires set by reentering debris around the world but global winter is the key i think.

 

 

Actually, the KT event was a meteor. There is considerable evidence -- including the crator at Chixulub in Mexico -- to refute this claim.

 

I'm not so sure it really matters, a comet of sufficient size would have the same effects as a meteor.

 

 

 

 

 

 

 

 

 

We need to look at this more carefully. Obviously, shrews did survive the KT event, as did other small mammals. Instead, it was the larger dinos that died.

 

I think we can only say the ancestors of modern shrews survived, we have no idea if these creatures were as specialized as modern shrews.

 

Your premise seems to be "no shelter". But smaller animals have a much better chance of finding shelter. They are smaller and the shelter is thus smaller. And, altho they eat more per body weight, the absolute amount of food they need per day is much smaller. Compare what an elephant and shrew needs per day. An elephant needs tons, a shrew an ounce.

 

Elephants do not eat tons of food a day, nor do they have to eat every day to survive, my point was that a larger animal with a slow metabolism is not as vulneralbe as a small fast metabolism animal.

 

So no, in the type of global winter envisioned after the KT impact, the larger animals are more vulnerable: less likely to find shelter, more surface area to radiate body heat, more food required. That is why the larger species died out at the KT and the smaller species survived.

 

 

Again, this is misleading, larger animals are less vulnerable than smaller ones to cold all things being equal. Larger animals require less food per kilo than small animals, larger animals have to eat much less often and can go longer periods of time with out food. All things being equal... The most likely unequal thing is that large animals cannot go dormant like small animals can.

 

 

A very small number of species survived; that's why it is a mass extinction. I would agree that it seems the burrowers had an advantage; that seems to be what happened with birds. Also species that could go into hibernation -- such as some species of turtles -- also had an advantage. However, estivation would not have helped since that takes heat, and the events after the KT were global winter. Not the right signals to put the animal into estivation. BTW, it's not really "pre-adaption" as evolutionists use the term. It's luck.

 

Define very small number of species... you are mistaken that estivation would not have helped, animals already in estivation (and around the world right now millions of animals already are) would have been protected. Animals can go into estavation and hibernation without the proper "signals" environmental stress can trigger both behaviors.

 

If anything estivation is more flexible than hibernation but both types of animals will indeed go into their respective modes of survival if the conditions developed that threaten their survival. But at any one time around the earth there are animals that are both in hibernation and estivation. So your point of a trigger is meaningless.

 

If anything the late Cretaceous was so warm that hibernating was probably an unusual mode of behavior for animals, estivation was probably more common due to the world wide warm climate

[lucaspa]

This is disputed, the main stream school of thought says this is sampling bias, not a true indication of declining dinosaurs...

 

You are going to have to document that "main stream school of thought". As far as I know, the "main stream" is that 1) dino populations were declining in numbers of individuals and species but 2) the meteor killed the rest. As an example: http://www.unmuseum.org/deaddino.htm

 

Notice that Horner is one of those documenting the decline; I doubt he and others are going to fail to rule out sampling bias.

 

There were almost certainly world wide fires set by reentering debris around the world but global winter is the key i think.

 

There perhaps were fires set around the world, but that is not the same as "fire storm".

 

I'm not so sure it really matters, a comet of sufficient size would have the same effects as a meteor.

 

Probably, but a comet comes in many smaller pieces spread out in space. Remember, most of a comet is ice and other non-rock materials. They don't have high levels of iridium. So the high levels of iridium in the K-T boundary strata, the shocked quartz crystals in the Atlantic, and the Chicxulub crator all refute the comet and support the meteor.

 

I think we can only say the ancestors of modern shrews survived, we have no idea if these creatures were as specialized as modern shrews.

 

But the ancestors were the same size as shrews, right? And your argument was based on size.

 

Elephants do not eat tons of food a day, nor do they have to eat every day to survive, my point was that a larger animal with a slow metabolism is not as vulneralbe as a small fast metabolism animal.

 

You are correct; elephants eat 300 - 750 pounds per day. But they do need to eat nearly every day. http://science.jrank.org/pages/2425/Elephant-Habitat-food.html http://www.mce.k12tn.net/animals/elephant.htm

 

They also need considerable amounts of water.

 

Elephants do not have a "slow" metabolism. Nor are they very well insulated. In these regards they would be similar to the large dinos with their warm-blooded metabolism but no insulating feathers or fur.

 

The point is that, altho smaller warm-blooded animals need more food per body weight than larger animals, the absolute amount of that food is much smaller. A shrew ancestor weighing 20 grams may require 40 grams of food per day, 200% of its body weight. But an elephant requires 159 kg or 159,000 grams per day. The same amount of food that an elephant eats in a day will keep a shrew ancestor alive for 3,975 days.

 

Again, this is misleading, larger animals are less vulnerable than smaller ones to cold all things being equal.

 

But all things are not equal. Leaving out the "dormant", smaller animals can find shelter easier than larger animals. Shrews today dig burrows, and the ancestors probably did as well. That provides shelter. They are often better insulated -- compare elephants to shrews. While larger animals can go a few days without food, their overall requirements for food are much are larger. A shrew can scavenge the 40 gm of food it needs per day and not miss a day, while that 40 gm is literally nothing to the requirement of an elephant. A fire that sweeps over the landscape will still leave small amounts of untouched vegetation. Of course, since shrews live on insects and worms, many of which are underground, it's even better for the shrew.

 

 

Birds, 0. For mammals, 1. For reptiles, it looks like 5-10. Same for amphibians. Insects, one genus.

 

You are arguing estivation, but the percent of species that estivate today, even in hot climates, is much smaller that the percentage that survived the KT extinction. And, of course, no bird species is known to estivate.

 

you are mistaken that estivation would not have helped, animals already in estivation (and around the world right now millions of animals already are) would have been protected.

 

Are you sure they would have been "protected"? How long would the winter have lasted? Not just a few days, but years. http://www.sciencedaily.com/releases/2010/03/100304142242.htm

 

" In both cases, new climate model simulations show that the effects would last for more than a decade." http://www.eoearth.org/article/Nuclear_winter

 

If anything estivation is more flexible than hibernation but both types of animals will indeed go into their respective modes of survival if the conditions developed that threaten their survival. But at any one time around the earth there are animals that are both in hibernation and estivation. So your point of a trigger is meaningless.

 

Is the trigger only conditions, or is it tied to seasons? For hibernation, much of the trigger is the length of the day, which causes the production of a protein Hibernation Induction Trigger. Is estivation similar?

 

Also, if estivation happens when the animal is not prepared for it with adequate fat reserves, won't it die if kept in estivation too long?

 

If anything the late Cretaceous was so warm that hibernating was probably an unusual mode of behavior for animals, estivation was probably more common due to the world wide warm climate

 

The Cretaceous up until about 400 ky prior to the KT impact was mild instead of hot:

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WD3-4SYTC4S-1&_user=10&_coverDate=12%2F31%2F2008&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1390334380&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=93e72baf9854ecb34c6967ca7e80dcb3

 

What I am reading is that the KT event caused the widespread death of plants in both the ocean and the land. The food chain collapsed. Larger herbivores would have died without enough plant material. The carnivores followed. Since most dinos and large aquatic reptiles were close to the top of the food chain, they starved. Smaller animals that had a more diverse diet, including a few species of birds, were able to survive.

[Moontanman]

You are going to have to document that "main stream school of thought". As far as I know, the "main stream" is that 1) dino populations were declining in numbers of individuals and species but 2) the meteor killed the rest. As an example: http://www.unmuseum.org/deaddino.htm

 

Notice that Horner is one of those documenting the decline; I doubt he and others are going to fail to rule out sampling bias.

 

A cryptozoology site? How about this?

 

http://www.falw.vu/~smit/forums/dinosaur_decline.html

 

 

 

 

http://paleo.cc/paluxy/maps97a.htm

 

 

 

http://www.sciencemag.org/cgi/content/abstract/254/5033/835

 

Results of a three-year field study of family-level patterns of ecological diversity of dinosaurs in the Hell Creek Formation of Montana and North Dakota show no evidence (probability P < 0.05) of a gradual decline of dinosaurs at the end of the Cretaceous. Stratigraphic reliability was maintained through a tripartite division of the Hell Creek, and preservational biases were corrected for by comparison of results only from similar fades as well as through the use of large-scale, statistically rigorous survey and collection procedures. The findings are in agreement with an abrupt extinction event such as one caused by an asteroid impact.

 

 

 

There perhaps were fires set around the world, but that is not the same as "fire storm".

 

I never said firestorm...

 

 

 

Probably, but a comet comes in many smaller pieces spread out in space. Remember, most of a comet is ice and other non-rock materials. They don't have high levels of iridium. So the high levels of iridium in the K-T boundary strata, the shocked quartz crystals in the Atlantic, and the Chicxulub crator all refute the comet and support the meteor.

 

I'll grant you that.

 

But the ancestors were the same size as shrews, right? And your argument was based on size.

 

 

No my argument is based on the cube square law...

 

You are correct; elephants eat 300 - 750 pounds per day. But they do need to eat nearly every day. http://science.jrank.org/pages/2425/Elephant-Habitat-food.html http://www.mce.k12tn.net/animals/elephant.htm

 

They also need considerable amounts of water.

 

So we are down from tons of food to a few hundred pounds?

 

A shrew sized animal will still starve far faster than an elephant sized animal. a human requires a certain amount of food a day too but that doesn't mean we will starve if we don't eat every day.

 

 

Elephants do not have a "slow" metabolism. Nor are they very well insulated. In these regards they would be similar to the large dinos with their warm-blooded metabolism but no insulating feathers or fur.

 

There have been cold adapted elephants, there were cold adapted dinosaurs, dinosaurs lived to with in 5 degrees of the poles, cold would not have killed off all the dinosaurs so this argument line is not relevant.

 

The point is that, altho smaller warm-blooded animals need more food per body weight than larger animals, the absolute amount of that food is much smaller. A shrew ancestor weighing 20 grams may require 40 grams of food per day, 200% of its body weight. But an elephant requires 159 kg or 159,000 grams per day. The same amount of food that an elephant eats in a day will keep a shrew ancestor alive for 3,975 days.

 

No, the amount of food an elephant requires is an average for mantaining good health, starvation takes a long time in elephants compared to shrews.

 

 

But all things are not equal. Leaving out the "dormant", smaller animals can find shelter easier than larger animals. Shrews today dig burrows, and the ancestors probably did as well. That provides shelter. They are often better insulated -- compare elephants to shrews. While larger animals can go a few days without food, their overall requirements for food are much are larger. A shrew can scavenge the 40 gm of food it needs per day and not miss a day, while that 40 gm is literally nothing to the requirement of an elephant. A fire that sweeps over the landscape will still leave small amounts of untouched vegetation. Of course, since shrews live on insects and worms, many of which are underground, it's even better for the shrew.

 

Define very small number of species...

 

Birds, 0. For mammals, 1. For reptiles, it looks like 5-10. Same for amphibians. Insects, one genus.

 

You are arguing estivation, but the percent of species that estivate today, even in hot climates, is much smaller that the percentage that survived the KT extinction. And, of course, no bird species is known to estivate.

 

 

 

Are you sure they would have been "protected"? How long would the winter have lasted? Not just a few days, but years. http://www.sciencedaily.com/releases/2010/03/100304142242.htm

 

" In both cases, new climate model simulations show that the effects would last for more than a decade." http://www.eoearth.org/article/Nuclear_winter

 

 

 

Is the trigger only conditions, or is it tied to seasons? For hibernation, much of the trigger is the length of the day, which causes the production of a protein Hibernation Induction Trigger. Is estivation similar?

 

Also, if estivation happens when the animal is not prepared for it with adequate fat reserves, won't it die if kept in estivation too long?

 

 

 

The Cretaceous up until about 400 ky prior to the KT impact was mild instead of hot:

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WD3-4SYTC4S-1&_user=10&_coverDate=12%2F31%2F2008&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1390334380&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=93e72baf9854ecb34c6967ca7e80dcb3

 

What I am reading is that the KT event caused the widespread death of plants in both the ocean and the land. The food chain collapsed. Larger herbivores would have died without enough plant material. The carnivores followed. Since most dinos and large aquatic reptiles were close to the top of the food chain, they starved. Smaller animals that had a more diverse diet, including a few species of birds, were able to survive.

 

A quick serach makes most of this a moot point... for both our arguments...

 

http://en.wikipedia.org/wiki/Cretaceous%E2%80%93

 

Tertiary_extinction_event

Omnivores, insectivores and carrion-eaters survived the extinction event, perhaps because of the increased availability of their food sources. At the end of the Cretaceous there seem to have been no purely herbivorous or carnivorous mammals. Mammals and birds that survived the extinction fed on insects, worms, and snails, which fed on dead plant and animal matter. Scientists hypothesize that these organisms survived the collapse of plant-based food chains because they fed on detritus or, in other words, non-living organic material.[7][12][13]

 

No hibernation or estivation required, scavenging seems to be a good thing to be able to do to survive an abrupt extinction event.

 

No doubt many factors resulted in the extinction/survival rates across the K/T boundary but the idea of a last lone dinosaur freezing in the blizzard is just a fantasy...

[sarco789]

A bit of speculation of my own. If anyone can contribute with evidence or relevant information I'd love to hear it.

 

 

 

Many now accept that the great extinction at the KT boundary was probably caused by an asteroid hit. One of the puzzles regarding that extinction is the selection of animal species, specifically dinosaur species surviving the catastrophe. We still have the birds with us, but in different forms to the archaic birds, and the non-avian dinosaurs are gone.

 

Has anyone suggested the following? Or, can you suggest a book or other reading?

 

Birds now largely have one of two mechanisms for attracting a mate; either gaudy plumage which they may display in some kind of dance, or singing. Not many use both. Off-hand I can only think of lyre birds.

 

By extension, it seems reasonable to think that the dinosaurs may have had similar behaviours and we know now that feathers were common among the dinosaurs. We also know that the feathers came in degrees; from a few plumaceous wisps to a full body covering.

 

The lucky survivors of the KT strike also needed to be lucky reproducers for their line make it through to the present. Could these lucky few have been the ones with a combination of (a) A full set of feathers (b) The habit of attracting a mate by singing?

 

A full set of feathers would be an aid to survival simply in the sense of being "body armour". And even feathers badly damaged in the strike and its immediate aftermath (heat, blast, atmospheric fallout, sulphuric acid rain etc) will regrow at the next moult if their owner has not been too badly damaged.

 

Feathers as insulators would also be hugely useful is the medium term as an aid to survival against the cold darkness of the "nuclear winter" following the strike.

 

However, in the darkness, which was deep enough to kill most of the plant life, a bird who tried to attract his mate with a plumage display would have severe problems. His prospective partners would not be able to see (and presumably admire) his plumage.

 

A bird who sang on the other hand, would be able to find his mate even in the darkness.

 

So, could the deciding factor in who survived the extinction lottery of the KT strike be

 

(1) A full set of feathers that would aid immediate survival

 

And

 

(2) Singing as the mate attracting mechanism

 

This has probably been suggested elsewhere, but I would like to read more developed explanations if anyone can tell me where to look.

 

Quark, interesting bit of speculation.

You're onto something when you analyze the survivors like that but don't forget Crocodilia in this analysis, who don't benefit from feathers or elaborate song, or extreme diversification. It was the mysteries of their physiology and their environmental adaptability, et al, that enabled them.

Also, remember that both of these surviving orders comprise branches of the basic trunk in the Archosaurian tree. Those that are extinct weren't meant for earth's more advanced stages of development, and they will never return as the dominant forms - perhaps in zoos.

Just look at them - everything typical of DINOSAURS made them targets for extinction. They are NOT representative of the Archosaurs, not the main thrust of the Archo line - Crocs and Aves are, and their success proves it (man's challenge is to remain until he can see what comes after the next global killer).

Dinos were an aberration during a very strange part of earth's past, and are a blind spot now, in the minds of too many "scientists".

Regards

[MonDie]

The feathered dinos were 1) larger and 2) carnivores. So they were more susceptible to the cold and their food supply died.

food supply died... or food supply was more mobile than the dinos, like the sky rats.

 

Also, we know about modern examples of smuggled, foreign species thriving due to a lack of natural predators.

Edited July 9, 2012 by Mondays Assignment: Die