Dinosaur Extinction

[Polycarp]

There are as many theories why the dinosaurs are no longer with us as there have been minutes since they departed this plane.

Two main ones:

1. The Louis and Walter Alvarez study that indicated a possible extraterrestrial impact (asteroid or comet) causing what was effectively a nuclear winter, with plankton dieoff, carbonated oceans, frigid temperatures worldwide, etc. Supporting evidence indicates a possible 200-mile-diameter crater centered on Chicxulub, Yucatan, Mexico.

2. Widespread volcanic eruptions causing similar phenomena. Supported by the eruption of the Deccan Traps, a multi-thousand-square-mile lava flow in peninsular India, dated to about this time.

Other hypotheses include ontogenesis (they evolved contrasurvival "adaptations" such as unwieldy size, a la Irish elk antlers, and died from them), loss of interest in sex, poisoning from alkaloids in angiosperms, racial senescence, etc. Then there are those that don't believe they were killed off by anything catastrophic but were on their way out, and one of the above simply finished the last survivors off.

I'm inclined to believe a combination of the two main ones is responsible, but with inadequate evidence to support this view. Anybody got additional information? Any other WAGs that deserve posting?

[AWB]

One theory I heard long ago was that plants had evolved to something inedible for dinos (flowering plants, I believe).

[Ukulele Ike]

Velikovsky! Velikovsky!
He's my man!
If his dinosaur-extinction theories don't do it for ya,
No one's can!

Velikovsky! Velikovsky! Velikovsky!

RAH!

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Uke

[Missy2U]

New fall lineup on Channel 7?

Sorry, couldn't resist.

[Earl Snake-Hips Tucker]

Racial senescence. Dinosaurs as a species had become old, and it was time for them to go.

[tracer]

Frogs evolved before dinosaurs did, and they're still here.

[Markxxx]

You forgot the third theory that dinosours didn't die out. They carry on today and are called "birds."

[Markxxx]

Sorry dinosaurs not dinosours. Oh well what are you gonna do? :)

[tracer]

And I just noticed: "Dinosaurs as a species"?!?! Heck, Dinosauria was a whole order of vertibrates -- that's three rungs higher than the "species" level on the taxonomic ladder.

Dinosaurs were on the decline at the end of the Cretaceous, though. Why that was, I have no idea. That's probably a bigger mystery than what eventually finished 'em off.

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Visit the Internet Stellar Database at www.stellar-database.com (http://www.stellar-database.com)

[Boris B]

Another theory I've heard is that mammals bread rapidly and found dinosaur eggs to be accessible and very nutritious. The first mammals are thought (by some, at least) to have been small semi-arboreal omnivores, difficult for dinosaurs to fight back against. I suppose this would make the first mammals somewhere between a tree shrew and a marmoset ... perhaps evolved from a warm-blooded tree lizarnd?

Anyway, I like this theory because it implies a sort of David-and-Goliath struggle, with wily little rodents eating dino omelets while T. rex dashed around impotently. But I'm know I'm just reading too much into it.

[Boris B]

Mammals bread rapidly? Sorry, I've got food on the brain today, even after two helping of cajun beans & rice.

[David B]

I think Gary Larson showed the real reason, in a classic Far Side-- they died from smoking.

[David B]

Ok, ok, now that I got that out of my system.

Polycarp, I think that #1 is pretty much accepted as the cause. Yes, there are still some who hold on to #2, but they definitely don't have consensus on their side, because the evidence has converted most everybody to #1.

[Earl Snake-Hips Tucker]

Give me a break, tracer. :( Other posters gave showed some levity, and you didn't pick on them.

[manhattan]

Levity? Levity? You dare call a reference to the greatest thinker of our century levity?

Why, Velikovsky’s observations are already being borne out by hee results coming back from hehe deep space probes. Not only that, but hehehe most of the so-called "debunkings" of hehehehehehe his work were poorly executed hehehehehehe hatchet jobs from so-called scientis.. heheheheheheheheheheheh.

Damn. Almost made it.

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Livin' on Tums, Vitamin E and Rogaine

[RTFirefly]

Personally, I like the Far Side cartoon about how the dinosaurs became extinct. ;-)

Actually, the crater wasn't the tipoff that there had been a cataclysmic comet/asteroid impact; there was a lot of evidence before its discovery that led them to look for the crater. A couple of decades ago, some scientists noted, at the boundary marking the end of the Cretaceous (sp?) period (is that the K/T boundary?) the presence of a substantially increased concentration of a rare element (iridium? I can't remember) found mainly in extraterestrial debris. Then other scientists found the same thing, at the same boundary, all over the world.

After that, a great deal of other supporting evidence was discovered to back up the asteroid theory. The crater was the smoking gun, so to speak. There's obviously no way to be certain of anything that happened over 100 million years ago, but it's a pretty safe bet that there was a cataclysmic impact of an object from outer space, at the end of the Cretaceous era, that was capable of causing a fairly major worldwide environmental impact all on its own.

Whether there were other cataclysms at the same time, and whether the effects of the impact were sufficient to snuff the dinosaurs all by themselves, I don't know. If the dinosaurs were cold-blooded (they're still arguing that one at great length), it seems pretty believable to me.

[DSYoungEsq]

Larson almost had it right. Dinosaurs died out from a high-fat, high-protein, low carbohydrate diet, which was offered to them to solve their cronic trouble with being over-weight.

As for Velikovsky, his work, while interesting, fails to take into account that the Earth was flat and only started moving around the sun in the Middle Ages... ;)

[Polycarp]

Sorry, RT, I hadn't intended to suggest the crater was the proof, but that it bolstered the proof. Point taken, and thanks.

David, not to contradict you (which I do enough of elsewhere), but two fairly recent (i.e., post 1994) texts, one on vertebrate paleontology and the other on historical geology, give arguments for and against both and do not indicate that the matter is felt to be decided, though to be sure the ET theory is shown as being more supported.

Bolstering the vulcanism theory is the fact that the only extinction event more thorough than the K-T (exit dinosaur) one was at the end of the Permian, and was matched by the only vulcanism even more widespread than the Deccan Traps, i.e., the Siberian Traps. (Inconsequential question: why "traps" for these? Anybody know? No derivation in the books I've read.)

Being an old SF/catatrophist fan from way back, I'm inclined to like the Giant Asteroid Finishes Off Dinosaurs headline over some blah lava flows, but I've got to admit that there is some good evidence for the latter.

[pldennison]

They were all burned at the stake by religious fundamentalists for existing when the Bible doesn't mention them.

[WallyM7]

Actually, Velikovsky was a misunderstood visionary, Manhattan.

He would have been hailed as the Polka King of Wisconsin had it not been...

Oh, wait. Are you talking about that flake Immanuel, or the band leader?

Never mind.

[DrFidelius]

The K/T boundary marks one of the major branching points in the multiverse. The dinosaurs are extinct because all of the time machines built in all of alternity to investigate the extinction of the dinosaurs happened to materialize on the same afternoon. Dinosaurs were crushed under the deluge of chronic argonauts.

Because temporal engineering requires a ceramic framework to contain the chrono-synclastic infundibulum, and the power source is an iridium isotope, the remains of the rag-tag fleet of time-line cruisers is today seen as the Alvarez stratum.


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Dr. Fidelius, Charlatan
Associate Curator Anomalous Paleontology, Miskatonic University
Cave ab homine unius libri

[Sam Stone]

Personally, I find it totally credible that Jupiter spat out Venus, which went by Mars and knocked it out of its orbit, and then went by Earth and dropped Manna from heaven (hydrocarbons, carbohydrates... tomato, tomahto), then Mars came by and parted the Red Sea, then came back and stopped the rotation of the Earth for a day, then went back into its original orbit, while Venus's elliptical orbit circularized over a couple of hundred years...

Or did I dream it?

[WallyM7]

I think everyone is in agreement that a major impact did occur around the time of the latest Great Dying. Whether this was the coup de grace or or the catalyst is still hotly debated.

It's my humble opinion that we'll probably never know for sure.

Infundibulum, incidentally, is not a hard and fast requirement for post-linear phase transigation, although it aids in the modificationalization of transverse corleumate.

Even I knew that.

[Snappy Plissken]

I thought the dinosaurs were thought now to not have evolved into pigeons and canaries...I mean, I myself can't picture iguanodons or spinosaurs chirping and flapping their arms like ducks...maybe they all went into the ocean and the deep dark forests of Canada and are merely hiding...or in our closets. I have a lot of junk in there...

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Snappy, The Crazy Toddite - Friend of Skippy

[Ukulele Ike]

Are you guys making fun of Velikovsky? You guys ARE making fun of Velikovsky, aren't you?

If I wasn't late for my lunch date with Horace Fletcher, William H. Bates, and T.D. Lysenko, I'd tear you nay-sayers a new asshole!

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Uke

[Ukulele Ike]

http://www.knowledge.co.uk/velikovsky/

I dunno if it's the best, but it's the first thing that came up on Google. Have fun!

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Uke

[David B]

Here's another: http://skepdic.com/velikov.html

[RTFirefly]

Wally, don't you mean the next-to-latest Great Dying?

[WallyM7]

I missed one? Damn!

[WallyM7]

Hmm, nope. Creteceous Period, 65,000,000 years ago - most recent mass extinction.


Almost had me there, RT.

[Polycarp]

Lessee...Great Dyings:

Maybe at the end of the Precambrian (~650 MYA)
End of the Ordovician (minor one) (~570 MYA)
End of the Devonian
End of the Permian/Paleozoic
End of the Triassic (~230 MYA, I think)
End of the Cretaceous (65 MYA)
End of the Pleistocene (20-10,000 YA)
End of the 20th Century (minus 3 months ago)
OK, the last one was just kidding.

Have I missed anything? Anybody have dates handy for the ones I missed?

[tracer]

DrFidelius wrote:

Because temporal engineering requires a ceramic framework to contain the chrono-synclastic infundibulum,

A Kurt Vonnegut reader, I see. :)

When I was 16, a guy I'd met up at music camp started using the term "chronosynclastic infindibulum" (or, really, his mis-remembering of it as "chronosynclastic parapinibula") as a code word for what he considered this really powerful mental state of super-analytic ability. In retrospect, I can see that the guy was a megalomanic; but at the time all I knew was that, if I bought into his claims about his mental state "discovery", I would receive godlike powers of mind over the universe.

At least the whole experience did get me thinking more about theoretical physics and cosmology.

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Visit the Internet Stellar Database at www.stellar-database.com (http://www.stellar-database.com)

[DrFidelius]

Guilty as charged, tracer. I take my inspirations from the best. Next I may have to admit to having read Brautigan way back in the fuzzy period of my life...

Great writers appropriate ideas, little writers steal them.

[WallyM7]

Polycarp, I beg to differ.

The extinctions that took place in the latter part of the Pleistocene were nothing more than a blip on the graph.

Nobody has ever called it a mass extinction, let alone a Great Dying.

[Persephone]

First thing I thought of when I saw the title of this thread was the Far Side cartoon.

Then I remembered another theory, that I saw on the front of a greeting card. A female dinosaur, wearing a dress, standing in front of a mirror and saying over her shoulder to her dino-hubby, "Does this dress make my butt look big?"

[Northern Piper]

okay, lysenko i know about - who is velikovsky?

[pldennison]

On the bus this morning, I was reading an article in the latest issue of Astronomy. The article was cataloguing various threats to life on Earth such as asteroid and comet impacts, solar fluctuations, etc. It mentioned that one type of threat occurs when our solar system travels through more dense and energetic portions of the galaxy, thanks to supernovae, gamma-ray bursts, and general exposure to the interstellar medium. Apparently some of these phenomena can cause the heliosphere to condense so that Earth's orbit lies outside, causing problems with the ozone layer, surface temperature, magnetic fields, and other things. It also mentions that some past extinctions appear to coincide with periods when the solar system was moving through denser areas of the galaxy.

I'll either find a link or post the relevant information myself later tonight.

[Persephone]

Next I may have to admit to having read Brautigan way back in the fuzzy period of my life...

It's okay to admit that sort of thing. I too have read Brautigan. But I haven't read any of these other people mentioned in this thread. Maybe I need to expand my horizons.

I'll be back later. Got to catch up on my extinction theory. After I go trout fishing.

[Momotaro]

The theory that dinosaurs starved because of the apparition of flowering plants is not supported anymore because it happened long before the KT boundary. The fossil record shows no large extinction related to the apparition of flowers.

The impact theory in which a large meteor falls to the earth and blows large clouds of dust in the sky, thus creating a nuclear winter effect, has serious shortcomings. Firstly, many impacts have occured during the time of the dinosaurs with barely any visible effect in the fossil record. Dinosaurs didn't seem to care. Secondly, the orthodox impact theory fails to explain how the dust could have stayed suspended long enough in the atmosphere to produce widespread ecological mayhem.

The issue is complicated. The extinction at the end of the Mesozoic era was not restricted to dinosaurs. Many marine life forms in the sea disappeared too. These include giant molluscs, and all species of large reptiles that roamed the sea at the time (ichtyosaurs, plesiosaurs, mososaurs(sp?), etc, which are only distantly related to dinosaurs). It also seems that mammals did not have an easy time of it either. As for birds, they might be counted as dinosaurs, but even in such a case, they represented only a small fraction of dinosaurian life forms. The pterosaurs, true flying reptiles, did not survive that great extinction either.

A modified version of the impact theory is that the Yucatan Impact was different in one respect. It is possible that the impact site contained a large pocket of sulfur. Sulfur is much lighter than the usual mix of rock that would get thrown in the atmosphere. It could have floated much longer and created a nuclear winter effect. Additionaly, the sulfur would have combined to form sulfuric acid, that would have returned to the earth in the form of acid rain. The effect on the plant life would have been terrific.

Whatever killed the dinosaurs, it seems to have affected most life forms. Maybe dinosaurs died because they were the most sophisticated animals of their time.

At the end the of the Mesozoic era something that endangered the whole food chain occured. The most advanced animals of the time, the dinosaurs at the top levels of the food chain, would have been the first threatened since their survival depended on all the other life forms below them. Mammals were generalists at the time, and that might have been the key to their survival.

I'd like suggest one more theory (to muddy things up). Continental drift might have contributed significantly to whatever stressed the food chain at the time. Most of the continents were touching at the time of the dinosaurs and had been moving away since the beginning of the Mesozoic. When the continents separated they opened new water ways. It's known now that the currents in the ocean have a very significant role as convection belts that carry heat from one region to the other and affect the environment greatly a la El Nino. These new water ways could have drastically changed the long established water currents and radically transformed the climate.

Of course, it's just a theory.

I don't know about the extinction at the end of the Pleistocene being just a blip. It may well be an ongoing process. The present rate of extinction is rather frightening. To our human perception, a few hundred species disappearing every generation might not seem like much, but it's beginning to compare with the extinction of the dinosaurs.

If you don't know what I'm talking about, you should know that the East Coast is experiencing serious fish depletion and that many large animals such as tigers and some species of rhinoceros might not survive beyond this generation. There is ample record of animals being already extinct because of us. We are experiencing one of the major extinctions of the earth, and we are the cause.




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Only humans commit inhuman acts.

[Earl Snake-Hips Tucker]

How about the temperature/sex theory?

Alligators' sex is determined by the temperature of the eggs.

Global climate changes could have caused dinosaurs to all be the same sex.

[WallyM7]

Momo, your post is well thought out and very reasonable.

However, I do not agree with your assesment of the extinnctions we are facing today.

I was talking about mass extinctions. Not species, not even genera, but classes and phylums dying out.

This is not the case today, nor was it in the Pleistocene.

[WallyM7]

Umm, excuse my ignorance.

I should have written Phyla.

[WallyM7]

Mj,

Good point, which is precisely the problem. Occam's Razor doesn't work here.

There are simply too many good theories going around.

Which is why I don't think we'll ever know for sure.

[Polycarp]

Momo, a nice response. If you're looking for picky precision, they're ichthyosaurs and mosasaurs (the latter of which you caught yourself).

I was under the impression that prior to the discovery of Chicxulub, all known astroblemes were either (a) fairly recent small ones such as the one in Arizona, or (b) large ones on geological shields, particularly the Canadian one, which were nearly all Precambrian in date. (There was IIRC one exception which was early Paleozoic.) This is all based on MFM (my faulty memory) so I welcome corrections.

Now, the impacts from this junk are proportional in some large ratio (as the square I think) to the size of the impacting body. If you drop a cobble-size rock or set off a firecracker in Serengeti Park, the animals do not all keel over and die. If, on the other hand, you set off a 50-megaton H-bomb there, there's a good chance they would. Likewise if you impacted it with a meteor one mile in diameter traveling at escape velocity or greater.

Something that produced a 200-mile-diameter crater in the Yucatan and sent tidal waves up the Gulf Coast and Mississippi Embayment (fossil evidence for this in appropriate formations) would probably produce enough impact energy to have the "desired" (i.e., interpreted) result.

As for dust in the atmosphere, it's quite capable of holding it for long enough. Stephen Jay Gould reports on the explosion of Tambora in Indonesia in 1815 and attributes the weather of 1816 ("The Year Without a Summer") to this. Krakatoa, only a fraction the size of Tambora's explosion, reddened sunsets around the world for over a year after, and the winter of 1888, far colder and snowier than normal, was attributed to its influence by some earth scientists.

Finally, among foraminiferans and other planktonic life, it appears that the survivors were those which were genetically capable of adapting to an extended cold period (e.g., encysting).

And of course I am fully aware that the dinosaurs were not the only things to become extinct. I simply used that as a short, catchy title for the thread. I could have called it "Hieronymus Bosch".... :)