K-Pg Extinction... Or Not?

[amargasaurus cazaui]

The comment was made the extinction event as a cometary impact is widely accepted...I dug up my book," Hunting Dinosaurs" as the tail end of the book is dedicated to precisely this debate and the comments of many of the todays leading paleo-experts are printed. Here are a few of the more succinct answers.

Bob Bakker " we will never understand the terminal Cretaceous exinctions until we look at all extinctions. Its not one crime of passion,in the ecosystem that killed off dinosaurs. ................"

Karen Chin " I think its a combination of factors. There probably was an asteroid impact sixty five million years ago.But I am of the its probably going to be more complex than we want school of thought....."

Ned Colbert " Its very hard to say. If it was a meteor, why didnt it kill turtles, crocodiles, birds, and mammals? The meteor would have to have been a smart bomb"

Phil Currie " I lean a little more toward the gradualistic reason..............."

Dave Gillette " I dont have a notion. I dont fully believe the single cause theories....."
Jack Horner " A comet killed the dinosaurs-all two of them. If not it was old age"
Neal Larson " They got to be too social......."
Giuiseppe Leonardi " I believe it was gradual.............."
Kevin Padian " I think that its environmental.............."
Paul Sereno " For the dinosaurs, I think climatic factors played a bigger role than the gradual ones...."
Philippe Taquet " I dont believe in catastrophic events......."
David Weishampel " There is a decline in hadrosaur diversity toward the end of the cretaceous, so that by the time you are at the very , very end , there were probably two or three kinds of hadrosaurs that were looking up into the sky watching an asteroid plunging into the atmosphere "

I question that the idea is prevalent or even generally agreed on these days. The various scientists quoted here are all of like mind .

[Simon]

A few thoughts on a topic that can never be 100% resolved due to their being no "instant replay" of the K-T "event"

1.  The alleged declining dinosaur diversity just prior to K-T is probably due to too few samples being available from just before K-T in too few places across the globe.  Logically a dominant species that took up every single significant niche for 200+ million years (including Pterosaurs and Sea going reptiles as well here) does not suffer a precipitous world-wide decline absent evidence of some radical cause.  No such radical cause has been found in the geologic record prior to K-T.

2.  Yes, the K-T "event" is overwhelmingly probable as the culprit for the mass extinction due to the simple fact that, in order to erase that many species in every corner of the globe, the event certainly has to be catastrophic and global in scope.  The asteroid impact is the only known candidate.

3.  The terrestrial dinosaurs, Pterosaurs and sea reptiles were wiped out due to a combination of many (most?  all?) of them being warm-blooded, as well as at the top of the food chain.  Warm-blooded animals - particularly large ones - must eat regularly to live - and cannot hibernate through a sudden global winter imposed overnight on a tropical and sub-tropical world, which wipes out all plant growth - the source of food that drives the entire higher food chain.  The vast majority were dead by the time the fires subsided and before the winter set in, raising the other question as to whether there would have been enough survivors (if any) to repopulate the earth.  Obviously the answer is that there were not.

4.  The animals that survived were either cold blooded  (deep sea fish) or able to hibernate through a global winter buried in mud (cold-blooded Crocs, turtles, amphibians which have a slow metabolism that they can slow further), or warm-blooded, small, with fur or feathers to help keep them warm, and the ability to hide in burrows and other sanctuaries (birds, mammals).  Just as obviously, such small warm-blooded creatures had ample food sources in the massive carrion covering the globe until the winter lifted and plants started to grow once again.

Without an "instant replay" we have to fall back on the most logical explanations, and the above points suggest strongly the K-T impact and its global aftermath as the sole reason for the great extinction at the end of the Cretaceous.

[amargasaurus cazaui]

The "kt" event has been renamed K-pg to make it reference more acurately the actual event . To use the term KT at this point is considered as invalid as most of the points being raised in an impact argument. The declining dinosaur diversity has been noted by many prominent paleotologists. It is not due to a lack of specimens for the appropriate levels, as you can quite easily find the boundary layer in almost any country you care to search. If the boundary is present, the fossils would be as well, and they are not. Reason, they were GONE already before the event. Simple concept.
   The cause of their decline is not absent and is also well researched and studied. The world was cooling, oyxgen levels were falling rapidly and the entire ocean that reached from Pennsylvania to Colorado disappeared. The world was in a massive period of changes and weather, and climate changes were drastic. This is known and established science and not something guessed at. The entire environment and atmosphere in a state of change and with it, the resulting stress on larger life forms was quite apparent and well known. The world was changing and the entire biomass with it.
The "KT Event" as it has been stated here is not overwhelmingly the cause and has been demonstrated for many reasons as not being.  The event while worldwide and drastic was not likely any form of impact or other worldy scenario. This is called Ghost in the machine logic, for when a clear situation isnt readily found and does not address the actual evidence at all.There were many other quite well established factors that were already contributing as I demonstrated above.In additon as I explained in my previous post, the Deccan traps were also in full swing far before the decline of the dinosaurs and throughout their subsequent end and yet apparently overlooked and not being considered despite the fact they alone could have provided the same level of damage to the environment. The asteroid impact is the only known scenario that does NOT fit the facts actually.
  The argument here assumes warm bloodedness for animals that are at this point undetermined for a starting basic flaw. Until or when this can be proven more likely, it is a THEORY, and not well researched science.In additon, not all of the species by far that went extinct were nowhere near the top of any food chain. As was stated, dinosaurs, but also many other lifeforms filled all niches of the ecosystem. Dinosaurs did retain the top levels in the food chain, but also the lowest levels as well, which makes that argument fundamentally silly.We lost not just dinosaurs, but species of plankton, not just dinosaurs but types of shellfish and fish. We lost varieties of insects. The indicator species for any ecological crisis , are generaly frogs , turtles, fish, and the smaller types that all swam right through the event and actually flourished. This alone indicates the reasoning behind an impact to be rather faulty.I am certain most birds, sharks, and fish do not hibernate? Somewhat surprised that card would even be played honestly.  And yet they came through this supposed "winter" with more diversity, and species than ever before .
  As for the carrion theory, would not most if it vanished in roughly a week? In an impact scenario with everything being incerated and the survivors dropping from starvation.....the carrion that was created in the event would not have lasted long ..so not sure how that helps the argument. Aside from the fact, if there were an impact, most carrion would be posioned by acid rain and made unuseable, another point most impact specilists seemingly miss.
  As stated, we do need to fall back on the most logical cause, rather than manufacturing a reason that fails to meet the availible evidence at any turn. Agreed.

[Simon]

Well, we agree to disagree.  I'll put it this way:  In my opinion you are "missing the forest for the trees".

P.S.  I used the term "K-T" on purpose because few things annoy me more than the arbitrary change of long-accepted terms.

P.P.S.  Did I mention that the capital of China is Peking?   

[tyrantqueen]

Oh, one other thing to mention about humans vs trex, is our adaptations for eating different foods. Dietary adaptations play a huge part in the overall adaptability of species. Humans have teeth that are adapted for consuming both plant and meat material, but without tools our consumption of meat would be limited to small animals that could be caught by hand, or to meat scavenged from the fresh carcasses of animals that have already died. Like modern day apes, we would probably have a mostly plant-based diet with meat playing little to no role. Trex could not eat plants, but he could he could hunt for meat. I would not be surprised if he could also scavenge carrion that would make most humans sick (but this is just speculation).  So regarding dietary adaptation in a real world scenario, humans would probably tie with trex again (humans eating mostly plants, possibly meat on occasion, trex eating mostly meat, possibly carrion on occasion).

Don't forget us humans can grow our own food As far as I know, we're probably the only species that does this on such a grand scale. And we have a whole culture devoted to it too.

Regarding the meteorite thing, can we make another topic devoted to it? I would like to see people's ideas behind this. For a long time I thought the K-pg event was the reason the dinosaurs were wiped out. It's interesting to see it being challenged.

[Simon]

*SNIP*

Regarding the meteorite thing, can we make another topic devoted to it? I would like to see people's ideas behind this. For a long time I thought the K-pg event was the reason the dinosaurs were wiped out. It's interesting to see it being challenged.

Well, people are curious creatures, very inquisitive and even more argumentative.  You don't get any publicity any more arguing FOR the K-T extinction event.  You now get some press by being a contrarian.  Just look up Horner, TRex Scavenger theory as another example of this type of purely human behaviour.

Occam's Razor, however, says that the K-T Yucatan impact caused the dinosaur extinction.  It is the ONLY theory that can explain the catastrophy of what happened to life on earth in its entirety.  Could there have been several other bollides that fragmented off the main asteroid as it made its way through the atmosphere?  Sure.  But that would only be corroborating evidence for the K-T impact theory.

[amargasaurus cazaui]

I do agree to disagree. The refusal to accept more modern terms, or knowledge is common and sometimes amusing in its own way too. Science is the ability to challenge known dogma as new information and facts present themselves. I prefer that approach myself. True there are some theories and people, ie Horner, that make a reputation making at time difficult to support ideas, but when the scientific community as  a whole tends to agree on a concept and refute a previously believed concept, there is normally a very good reason.
  There are many well written pieces on this topic within the last several years that do a rather nice job of refuting the entire impact scenario. I also quoted most of the more well known paleolontologists debunking it as well. You have Sereno, Bakker, Ostrom, Currie, Chin,Horner  and a list more besides that all agree with the facts more than the science fiction. A single impact is already known to be incorrect and indeed it was likely a multiple impact following the Deccan traps event, but even then the dinosaurs were well on their way out. The paleontologists I quoted go on to offer more support for their comments in the book as well. I simply downsized them for conveinance sake. A copy of the book, "Hunting Dinosaurs" might come in handy.
I also provided many facts and supporting evidence for my argument rather than just saying...It is what I say !!! 
  We may never know precisely what happened during that time period or what killed the dinosaurs. The fact the dinosaurs survived more than 70 meteor impacts through their reign, many of much grander scale seems to escape most determined impact lobbyists.
  I may have trouble seeing the forest, but I am sure it isnt because a meteor destroyed only it and left all other forms of life present.
Finally , I agree, you do not see people arguing about or discussing the KT event anymore. As I stated, the name of the event was changed some time back. As for Occams razor it is a lovely utility but only when applied properly. The simple thing you ignore when oversimplifying this using "Occams razor" is there were MANY more impacts over the reign of the dinosaurs that did not cause extinction, and there were MANY MORE EXTINCTIONS that also did not require a meteor in the Yucatan. 

[Simon]

I hope that by the "science fiction" dig you are not saying that there was no "K-T" impact?

That would be ... heretical ...

In any event, all I am saying is that looking at this logically, I can only come to one conclusion based on the evidence that I am aware of.

P.S.  The dinosaurs could not have died out because of nit-noid events because:

1.  They survived 220 MY of climate change, continental drift, etc, just fine;

2.  They were much too cool and superior to puny mammals that I refuse to believe otherwise - it had to have been an "Act of God" as an old saying would go ... 


I was going to leave it there, but what the heck, its very late and I'll ramble a little bit since you don't appear to have understood the significance or the import of some of the points I made upthread:

Seriously, of course there were many impacts and extinctions of particular species whose niches were taken over by other dinosaurs.  That last part is just how life works.  The measurable fact is that this one impact appears to have been a whole lot worse than the other ones.

BTW, there is also an ash layer along with the iridium that testifies to a global firestorm.  As far as no mass graves being found, well, fossils are made over eons.  If all animals died suddenly, it would be unlikely that you would happen to find one of them versus generations that died in the previous, say 100,000 years.  (Although there does appear to be a 40-mile fish fossil graveyard in Antarctica that dates right around the K-whatever "event". (Or so I read a few years ago.)

A couple of other loose points - the carrion would have lasted the global winter.  I would imagine that it didn't take too long for that winter to begin after the impact and resulting global firestorm darkened the sky.

The ability of Frogs, Crocs and turtles to survive underground is well documented.

There are Crocs today that live around several oasis in the Sahara Desert (reread that line).  During the long months that the water disappears, they bury themselves in the mud which then dries out and becomes rock hard.  When the water returns and the mud softens, they awake.

Hence, it is not a problem for the K-T extinction theory that these creatures got through the event "swimmingly", in fact it is consistent with that theory, not an argument against it.  It is exactly what you would EXPECT to see.

(It is again worth noting that the global winter with temperatures well below freezing hit after a global firestorm that basically turned the forests of the earth into ash - and it hit a world that was tropical and subtropical - meaning that none of the larger animals had any experience - or evolutionary strategy - to deal with that winter.)

But in any event, 99% of large animals were probably dead within a few weeks of the impact.  See, if the impact really wasn't as bad as all that, you would expect some larger animals to survive - life is very hardy, surviving many other bad events - as you point out.  The very fact that NONE of the larger animals survived is further logical evidence as to the CATASTROPHY of the K-T impact.  This is an important point for you to think about.  If the impact was not all that terrible, the dinosaurs would still be around (well, besides birds, I mean.)

Real simple, really - big, warm-blooded critters - IF they even can survive this global "nuclear blast" - face no food, no shelter, can't hibernate - death is certain.

Cold blooded burrowers - well, they can make it.  Ditto for small feathered birds roosting underground and small furry rodents.

Once you understand the dynamics of the asteroid impact and its immediate consequences, the animals you would expect to die off - DID die off.  Suddenly, just as you would expect.  The animals that you would expect to survive - DID survive.

Lastly, the fact that this asteroid hit at such an angle that spewed fire directly across North American and beyond, as well as the fact that it hit a load of sulphur-rich rocks appears to have made the effects of the impact worse than they would otherwise had been.

Its not 100% provable, but it IS a logically defensible position.  The folks you quote are citing minutiae that may or may not even be accurate (due to the tiny size of the available 65MYA samples of dinosaur fossils world-wide) in some cases. One has to pull back and see the global view.  Total Extinction indicates Total Annihilation which equals - in this case - the Chixculub crater as the culprit.

[Gwangi]

I don't know a lot about the extinction event that killed off the dinosaurs, it never interested me much. What is more is that I have always thought the asteroid impact was the obvious culprit. I still do, and I know we've argued about this before. It seems awfully coincidental that this known event happened at the same time non-avian dinosaurs died off.
Amarge, you keep mentioning the latest science and evidence and current thinking but despite all the claims you only reference the book "Dinosaur Hunters" which is 15 years old, perhaps an updated version of the book has been made? Searches on Amazon yield nothing. Actually if anyone knows of a recent book on dinosaur extinction I would appreciate knowing about it, it is a subject I would like to brush up on.
You say that most scientists now agree that the asteroid impact was not the main cause of the extinction event. This is news to me. Everything I have read claims that the asteroid impact is widely agreed upon at this point. There is growing evidence for the Deccan Traps being involved but at the moment the consensus  is "the astroid done it". I looked to a recent book for more information. "The Princeton Field Guide to Dinosaurs" by Greg Paul. He discusses the Deccan Traps with the following...

"Massive volcanism occurred at the end of the Cretaceous as enormous lava flows extending 1.5 million square kilometers covered about half the Indian subcontinent. It has been proposed that the air pollution produced from the repeated supereruptions damaged the global ecosystem so severely that dinosaur populations collapsed in a series of stages, perhaps spanning tens of thousands of years. This hypothesis is intriguing because extreme volcanic activity also occurred close to or during the great Permo-Triassic extinction; those eruptions were in Siberia. Some geologists, however, question whether the Indian volcanism occurred at exactly the same time the dinosaurs went extinct. Nor does the volcanic hypothesis readily explain why dinosaurs failed to survive problems that other continental animals did."   

That makes me wonder. You're speculating how animals could survive an asteroid impact. I on the other hand am wondering how volcanic eruptions spared the same animal species. Either way the question needs answering. I have an easier time thinking that an asteroid impact would be more selective than a volcanic eruption. Regardless, both events did happen.

He goes on later to say...

"There is widespread agreement that the K/P extinction was largely or entirely caused by the impact of at least one meteorite, a mountain sized object that formed a crater 180 km (over 1000 miles) across located on the Yucatan peninsula of Mexico."

He concludes with...

"A combination of events may have collaborated to kill off the dinosaurs. It is possible that nether the impact alone nor the Indian eruptions on their own would have proven so lethal, but the one-two punch may have done the job. It is possible that more than one impact may have occurred. It has been suggested that the seismic activity initiated by the impact could have set off the Indian eruption, but the timing of those events is not yet well enough understood to tell, and some suggest the lava flows had already so severely damaged the dinosaur fauna that the impact was able to deliver the coup de grace."

I will acknowledge that the Indian eruptions may have played a part in dinosaur extinction, the evidence is there. The evidence is also there that an asteroid did the job, it is damn good evidence (the best we have) and certainly not science fiction. Even if it initiated the eruptions the impact would have been the catalyst behind the extinction. If it occurred after the eruptions began it was the tipping point needed to kill off animals that would have likely survived otherwise. So some dinosaurs were found above the iridium layer, so what! I'm sure some dinosaurs survived the initial event, maybe even for quite some time. Just not enough to recover the population.

As for the rest of the extinction theories that exist, none of them can account for the massive loss of life. Sure the earth was changing; the fauna, climate, geography. Whatever! Dinosaurs were the dominate terrestrial animals for 160 million years! None of those events would cause a world wide extinction of every non-avian dinosaur group in addition to marine reptiles, pterosaurs and scores of other species. "Change" being the culprit is a lazy answer. Change does cause extinction, it also encourages evolution. The scale of extinction that occurred can not simply be answered with the planet changing in its natural course. The dinosaurs witnessed more than enough change during their time on earth and seemed able to adapt well enough.

Now, as for the proposed decline of the dinosaurs before the extinction event. Perhaps they were in decline but they weren't gone, your bones above the iridium layer prove that. Even if they were in decline (and while some say they were others say they were not) they would not have gone completely extinct without some sort of environmental catastrophe. If an asteroid happened to hit the earth at the same time dinosaurs were in decline it would still be the ultimate cause of their extinctions. Same if they were thriving. Greg Paul discusses this as well...

"It has been argued that dinosaurs were showing signs of being in trouble in the last few million years before the final extinction. Whether they were in decline has been difficult to verify or refute even in those few locations where the last stage of the dinosaur era was recorded in the geological record, such as western North America. Even if true, the decline was at most only modest."

Ultimately we don't have enough fossil evidence to claim dinosaurs were in any serious decline. Only one fossil site that I'm aware of exists that gives us a look into the last days of the dinosaurs. That is of course western North America. At that site we have Tyrannosaurus, Triceratops, Pachycephalosaurus and Ankylosaurus to name a few, all of them were the largest known examples of their respective groups.

[wings]

@Gwangi
not sure about books but there is a paper recently came out about the topic called "Dinosaur extinction: closing the '3 m gap'" (http://rsbl.royalsocietypublishing.org/content/early/2011/06/29/rsbl.2011.0470.full.pdf)

I don't have much interest in extinction either, but after reading these comments and that got me thinking, I was wondering what happened to the enantiornithes birds? Somehow they all died out as well at the K-T boundary but the ornithurae birds survived. These birds are similar in "size" and probably have very much alike physiology, also there is no indication of enantiornithes declining in number near the end of Cretaceous. So following the same logic so far the enantiornithes should have survived this catastrophe (asteroid impact) like the other "smaller" critters. This is just a random idea and by no mean an argument on this debate.

[amargasaurus cazaui]

Apparently noone grasped what my position was from my comments.

My primary statement is the dinosaurs were not made extinct by the cometary impact event primarily. I made a strong case they were in decline far before the event, and also the causes for it. The Deccan traps erupted prior to the comet impacts , at roughly 68 million years if not earlier. The sheer power of these eruptions ALONE was capable of destroying the biomass present , and quite capable of stressing a worldwide ecosystem of life into major stress and extinction patterns. This is hardly new nor cutting edge science and is documented in books and papers quite adequately. When you then factor in the massive climate changes that were also being factored into their already badly damaged ecosystem, it is a quite simple deduction to see what happened. What was new for the dinosaurs and had been somewhat constant during their reign was oxygen content. The oxygen content was dropping rapidly due to the death of so much plant material, the clouding of our atmosphere, with the effects from the eruptions, and the runaway ecological disaster in the making already.Again, measureable by simple lab testing on pure air bubble samples within amber, that demonstrate this is precisely the case. From the Jurassic all the way through the Cretaceous the oxygen level for these animals was dropping and continues doing so. In return you can measure a downsizing of the life on the planet from the Jurassic giant herbivore sauropods, through the Cretaceous to smaller kinds and types of dinosaurs, down into the mammalian age, with its mammoths, and larger lifeforms which are also now gone. As the oxygen level drops the lifeforms become smaller.When you consider how massive they were, much of their lifestyle and basic everyday activity would have been impossible in an atmosphere depleted of as much as a third of its oxygen. As the previous posting stated, the destruction centered around the larger lifeforms, the very ones that require the most oxygen. I somewhat missed where it was explained how birds, sharks and fish all stopped swimming, apparently dug holes and went comatose while a nuclear winter event eliminated the world of its lifeforms, as they consumed frozen acid rain poisoned carrion.  I saw some discussion centering around animals that are known to hibernate, which is of course not even contested. Aside from those massive flaws in the argument, what of the Larger animals in the oceans that managed to survive...the sharks as i mentioned in particular? The larger fishes and so forth? Could it be because they have low oxygen requirements?
  This is why dinosaurs are seldom found close to the K-pg boundary, For the most part they were already gone. Yes , there were pockets of survivors found in various places, however the population as a whole had been reduced to extinction levels. The most well documented find of post impact dinosaurs in fact occurrs in a shallow depression of the Mexican isthumus, barely two hundred miles from the impact site, in the San Juan valley.  If you ever wish to prove for yourself how badly the speciating of the various dinosaur lines had decreased, look at the timelines for duckbill dinosaurs, and at what point they were most species rich and how many were known to exist at the K-pg.....or horned dinosaurs for that matter, or sauropods.....or any other dinosaur family you might select for that matter. The number of new species being introduced was declining massively and this is why the Jurassic is often called the golden age of dinosaurs.
I am not that impressed with the studies trying to count individual skeletons, but just looking at the overall species pattern one can see quite clearly the dinosaur lines were faltering, and the line was coming to a close far before said event.
    I do allow there was an impact, in fact several of them. I myself was the one who first mentioned the sites in northern Russia, Silvertip, as well as Shiva, which actually was likely the final event, rather than the impact in the Yucataan.And just as most of the paleontologists I quoted stated, I feel the comet did elimate the last of the dinosaurs.....all two or three of them that were standing there watching it plunge into their atmosphere.
    This was not a simple comet, bang, your done dinosaurs thing. It was much more elaborate and spread over a much longer time period as the fossil evidence shows. The earth was badly stressed far before the impacts as shown in the fossil record, and far after.
    The book I am referencing, "Hunting Dinosaurs" not "Dinosaur Hunters" was published far after the comet impact theory was introduced and the only thing I have seen in print that actually shows you around thirty of the foremost paleo-experts in the world sounding off on the topic, which is why i quoted from it. If you wish to read about dinosaur extinction there are quite a ton of books out there, which discuss the topic in depth. I have to state that I see few books with copyright the past ten years attempting to state categorically this was a cause and effect event. Most authors and research experts have become familiar with the many flaws in the argument originally presented. You quoted from Greg Paul, in his book, and much of what he said does agree with my comments.


He concludes with...

"A combination of events may have collaborated to kill off the dinosaurs. It is possible that nether the impact alone nor the Indian eruptions on their own would have proven so lethal, but the one-two punch may have done the job. It is possible that more than one impact may have occurred"

He is saying the exact thing I am...word for word right? This is the modern paleontologist take as a whole that I get from practically every book I see. They too, no longer subscribe to the single killer mechanism , as it just does NOT hold up to scrutiny. I think you answered your own question with your own book...yet another book that does not accept the impact scenario as the conclusive cause and effect end of the dinosaurs.
  Change is not a lazy answer. Summoning up some cosmic specter to do the dirty work is. Change is and can be the cause and often is, depending on what that change IS. If in your mind it was simply weather patterns, no, that was one factor. The net result was lost of oyxgen, which is change and was deadly.
  Your argument states, climate, fauna, geography were all changes the dinosaurs were used to and therefor could not cause their extinction but fails to address the rather crucial evidence that were at least 70 known bolide impacts worldwide that were during the dinosaur reign which all failed to produce extinction . Aside from the fact the impact in the yucatan falls in something like sixth place in size, and was far outdone by other impacts in size, scope and traceable remains. ie...the impact site in chesepeake bay or the northern canada impact site, or the massive impact in Africa....these were all much larger strikes that were far more deadly, and did not cause a blink in dinosaur history we are aware of. So it does seem rather shoddy logic to say it could not be weather, geography or climate and had to be an asteroid because dinosaurs were used to dealing with those factors, when clearly they had also dealt with asteroid and bolide impacts uncounted for millenia as well.
Finally regarding the Yucatan event, I noted the comments about the sideways impacting of the bolide in that site. The comments about a firestorm then blasting the north American continent etc.....again more badly distorted information. The consensus at this point suggests the comet came at such an angle to place the trajectory of its blast and forward momentum out over the Pacific region, and there is physical evidence in the oceanbed to substantiate this fact. If you somehow manage to swerve the impact, so that it turns halfway around in its impact angle and trajectory you might achieve the effect you are shooting for, but at this point the angle and longstretch of the crater, do not support an angle aimed at the north American mainland itself at all. The effects, while being massive and widespread would have been disastrous, but stating it was somehow deflected to blast the north American continent was disproven quite some time ago.


and I do agree, this topic needs its own thread , it appears to have gained some life of its own, if someone would be so kind to oblige...thanks

[amargasaurus cazaui]

Ultimately we don't have enough fossil evidence to claim dinosaurs were in any serious decline. Only one fossil site that I'm aware of exists that gives us a look into the last days of the dinosaurs. That is of course western North America. At that site we have Tyrannosaurus, Triceratops, Pachycephalosaurus and Ankylosaurus to name a few, all of them were the largest known examples of their respective groups.

I thought to also respond to this point. The Chinese finds from the Cretaceous era, then are what?  Are we attempting to state here the only exposed fossil bed for late Cretaceous finds is the Western US?  What of the finds in Russian, Mongolia, and Africa? And honestly....Tyrannosaurus, Nanotyrannus, largest, smallest. Triceratops, Microceratops. Pachycephalosaurus, Dracorex..etc....what does size prove? They existed alongside some of the smallest of their kinds as well.

[amargasaurus cazaui]

I thought I would also comment on the somewhat questionable concept that all dinosaurs would have been from  tropical and sub tropical areas. We know from many well documented finds that dinosaurs existed on every known land mass, including the poles, greenland and alaska, where there were winter conditions for as much as nine months. In the series WWD they devoted an entire episode to dinosaurs capable of living in winter environments and that were able to hibernate. In additon many of the findings of dinosaurs in these cold zones are infant and small dinosaurs which suggests they were not just migrating and resided there year round. Yet now suddenly the cold conditions brought on by an impact would kill them....you cannot really have it both ways, either they could or could NOT. The fossil record seems to indicate could, did and had no problem at all with it. Which makes the concept of a winter brought on by an impact as a killer mechanism rather questionable.

[Simon]

I thought I would also comment on the somewhat questionable concept that all dinosaurs would have been from  tropical and sub tropical areas. We know from many well documented finds that dinosaurs existed on every known land mass, including the poles, greenland and alaska, where there were winter conditions for as much as nine months. In the series WWD they devoted an entire episode to dinosaurs capable of living in winter environments and that were able to hibernate. In additon many of the findings of dinosaurs in these cold zones are infant and small dinosaurs which suggests they were not just migrating and resided there year round. Yet now suddenly the cold conditions brought on by an impact would kill them....you cannot really have it both ways, either they could or could NOT. The fossil record seems to indicate could, did and had no problem at all with it. Which makes the concept of a winter brought on by an impact as a killer mechanism rather questionable.

Actually, without realizing it, you have actually made my point in a way.  The poles were so warm that animals lived there year round and temperate rain forests existed.  When the global winter hit, the poles would have been plunged to the coldest temperatures on the planet.  Well below freezing for months.  And after everything had first been burned up.

[Simon]

03/04/2010 Article from Science Daily on Journal of Science study that concluded that asteroid caused dinosaur extinction:

http://www.sciencedaily.com/releases/2010/03/100304142242.htm

[amargasaurus cazaui]

I thought I would also comment on the somewhat questionable concept that all dinosaurs would have been from  tropical and sub tropical areas. We know from many well documented finds that dinosaurs existed on every known land mass, including the poles, greenland and alaska, where there were winter conditions for as much as nine months. In the series WWD they devoted an entire episode to dinosaurs capable of living in winter environments and that were able to hibernate. In additon many of the findings of dinosaurs in these cold zones are infant and small dinosaurs which suggests they were not just migrating and resided there year round. Yet now suddenly the cold conditions brought on by an impact would kill them....you cannot really have it both ways, either they could or could NOT. The fossil record seems to indicate could, did and had no problem at all with it. Which makes the concept of a winter brought on by an impact as a killer mechanism rather questionable.

Actually, without realizing it, you have actually made my point in a way.  The poles were so warm that animals lived there year round and temperate rain forests existed.  When the global winter hit, the poles would have been plunged to the coldest temperatures on the planet.  Well below freezing for months.  And after everything had first been burned up.

Not year round, and not likely even half the year. Did you see the program WWD for instance where it dealt with this issue? Global winter? Everything burned up? This is the science fiction part I referrred to. Sorry

[amargasaurus cazaui]

03/04/2010 Article from Science Daily on Journal of Science study that concluded that asteroid caused dinosaur extinction:

http://www.sciencedaily.com/releases/2010/03/100304142242.htm

I did read the article and thanks for sharing it Simon. I think we may never know definitely the answer here, but in their conclusions I am left with quite a few rather serious questions. For me at least I think the first thing I would be asking is who chaired and membered the panel? If this was the same group , containing members from the original team, that first proposed the impact scenario, It would tend to bias their work. This has been the case with many of the supposedly "new" studies done since. I did not see anything new being offered as evidence in the article.
    Was there an actual paper released for this study that gives anything for hard facts, or helps state their reasoning and methods for making this determination? I would doubt it exists, but if such paper was released I would like to review that for certain. I myself would benefit greatly from seeing where they went, what they examined and how they measured the various factors used to make such a determination.
   Both sides of the debate do and have had their supporters for years, and probably always will. I wish we had more evidence to support this claim, but at this point the evidence being used to support an impact could as easily be explained in other ways .
  You easily see that for yourself by reading the article, because right alongside it on the same page are three or four other articles offering seemingly as solid evidence against the impact scenario
  I did want to say again thanks for sharing the article Simon. I will research further into their work and see if anything more definitive from them is to be had..ie a serious paper, or some sort of published work we can go through

[Gwangi]

"Hunting Dinosaurs" or "Dinosaur Hunters", whatever. I looked up your book and the date of publication is 1995. You're right, what you are presenting is not new nor cutting edge science, some of it might actually be outdated. I'm looking up the various points your trying to make and finding that the consensus still remains among scientists that the asteroid impact is what sealed the deal for the non-avian dinosaurs. I looked up the Deccan Traps on wikipedia, I got this...

"Because of its magnitude, scientists formerly speculated that the gases released during the formation of the Deccan Traps played a role in the Cretaceous–Paleogene extinction event (also known as the K-Pg extinction), which included the extinction of the non-avian dinosaurs. Sudden cooling due to sulfurous volcanic gases released by the formation of the traps and localised gas concentrations may have contributed significantly to mass extinctions. However, the current consensus among the scientific community is that the extinction was triggered by the Chicxulub impact event in Central America (which would have produced a sunlight-blocking dust cloud that killed much of the plant life and reduced global temperature, called an impact winter)."

The Shiva crater you mention, I read about it. I got this...

"A geological structure exists in the sea floor off the west coast of India that has been suggested as a possible impact crater, in this context called the Shiva crater. It has also been dated at approximately sixty-five million years ago, potentially matching the Deccan traps. The researchers claiming that this feature is an impact crater suggest that the impact may have been the triggering event for the Deccan Traps as well as contributing to the acceleration of the Indian plate in the early Paleogene.[10] However, the current consensus in the Earth science community is that this feature is unlikely to be an actual impact crater."

This is why dinosaurs are seldom found close to the K-pg boundary, For the most part they were already gone. Yes , there were pockets of survivors found in various places, however the population as a whole had been reduced to extinction levels. The most well documented find of post impact dinosaurs in fact occurrs in a shallow depression of the Mexican isthumus, barely two hundred miles from the impact site, in the San Juan valley.  If you ever wish to prove for yourself how badly the speciating of the various dinosaur lines had decreased, look at the timelines for duckbill dinosaurs, and at what point they were most species rich and how many were known to exist at the K-pg.....or horned dinosaurs for that matter, or sauropods.....or any other dinosaur family you might select for that matter. The number of new species being introduced was declining massively and this is why the Jurassic is often called the golden age of dinosaurs.

He is saying the exact thing I am...word for word right? This is the modern paleontologist take as a whole that I get from practically every book I see. They too, no longer subscribe to the single killer mechanism , as it just does NOT hold up to scrutiny. I think you answered your own question with your own book...yet another book that does not accept the impact scenario as the conclusive cause and effect end of the dinosaurs.

Absolutely not. Greg Paul does not state that dinosaurs were in decline before the extinction and if they were it was modest. You're claiming they were basically extinct by the time the asteroid hit. See the difference? Regardless he also states that the current consensus (as in 2010 when the book was written, not 1995) is that the asteroid impact was the leading cause behind the extinction.

Change is not a lazy answer. Summoning up some cosmic specter to do the dirty work is.

Summoning up? There is no summoning here, the asteroid impact theory is widely agreed upon because of scientific evidence! I'm not going to get into the iridium layer at this point but since you seem to think there was an environmental cataclysm that latest for millions of years I will give you a Scott Sampson quote from his 2009 book "Dinosaur Odyssey"...

"On the biological side, paleobotanists have documented a radical decimation of plant life at the end-Cretaceous boundary. Just below the iridium layer, fossil pollen and spores from many locations around the world indicate a diverse flora. Immediately above this layer, the pollen and spore evidence is heavily dominated by a single type-- ferns. Ferns are one of the first plants to recover after major environmental catastrophes, and this "fern spike", as it's been called, is cited as evidence of a sudden cataclysm--that is, death by silver bullet."

Aside from the fact the impact in the yucatan falls in something like sixth place in size, and was far outdone by other impacts in size, scope and traceable remains.

Where do you get that kind of information? I just looked it up, the Yucatan impact crater is the third largest on the list! Look for yourself. The two that are larger occurred before the Mesozoic and your Shiva crater might not even be an impact crater.

I thought to also respond to this point. The Chinese finds from the Cretaceous era, then are what?  Are we attempting to state here the only exposed fossil bed for late Cretaceous finds is the Western US?  What of the finds in Russian, Mongolia, and Africa? And honestly....Tyrannosaurus, Nanotyrannus, largest, smallest. Triceratops, Microceratops. Pachycephalosaurus, Dracorex..etc....what does size prove? They existed alongside some of the smallest of their kinds as well.

Yes, that is what I'm attempting to state. The sites you mention are all older in age than the formation in North America. Scott Sampson claims...

"The fossil record of dinosaurs is remarkably sparse for the final stage of the Mesozoic. Indeed, to date, only one place on Earth--- the Hell Creek Formation exposed most abundantly in eastern Montana and Dakotas--- has been investigated in detail."

What does size prove? Aren't you the guy who just argued that dinosaurs got smaller and less diverse due to a dwindling oxygen content? If that were the case how could some of the largest dinosaurs known, have lived at the end of the Mesozoic? And oh yes, Nanotyrannus and Dracorex are probably juvenile stages of larger dinosaurs. If they are their own species then they only show dinosaur diversity was higher than if they weren't. Microceratops is of no value here, it lived 90 million years ago, not 65.

You claim no scientists subscribe to the "silver bullet" hypothesis. You also claim that the dinosaurs were obviously already in decline. Scott Sampson has this to say...

"For a long time, I regarded myself as a card carrying member of the gradualist-Blitzkrieg camp. However three lines of evidence have caused me to change my mind and join the ranks of the silver bullet enthusiasts. First is the documentation of many additional K-T boundary sites preserving that anomalous iridium layer; the presence of this asteroidal signature at far-flung locations around the globe confirms that the Chicxulub impact was truly a devastating, global event. Second is a growing fossil database indicating that the terminal Cretaceous world was not stressed to the breaking point, awaiting arrival of an extraterrestrial coup de grace. With regard to dinosaurs in particular, recent work in the Hell Creek Formation and nearby Lance Formation have documented a much more diverse fauna than previously realized. Certainly some dinosaur lineages (e.g., short-frilled ceratopsians and crested duck-bills) went extinct prior to the end of the Cretaceous, but overall dinosaur diversity remained relatively high, with many groups represented by truly gigantic exemplars such as Tyrannosaurus, Ankylosaurus and Pachycephalosaurus."

"I see no grounds for arguing that dinosaurs (or other groups of animals or plants) were undergoing a slow, attritional demise in the latest Cretaceous. We must keep in mind however, that our knowledge of dinosaur diversity at the very end of the Cretaceous is limited to one place in western North America...Finally, it seems questionable to argue for a lethal cascade of agents when compelling evidence exists for a single agent capable of doing the job on its own."

[amargasaurus cazaui]

No not whatever, Dinosaur Hunters is entirely a different book, I own them both, PLease do not place me in direct miscontext of my comments.It is not very polite nor appreciated . I do not misquote you, so please stop doing it.   I referred to the book "Hunting Dinosaurs " as it does provide the quotes i used. Thanks !!! Yes you are correct, not new nor cutting edge, just accurate and generally accepted by most.  Lets follow your points one by one to their logical conclusions here.
  You did look up the Deccan traps apparently and then took the comments which were in favor of your argument out of context of the rest of the commentary sadly. Being fair, perhaps you should have posted them in entirety and allowed others to view the opposing viewpoint rather than condensing to meet your own criteria. Similar thing with the Shiva crater, the article clearly states the presence of iridium, shocked quartz and a rebound peak , the very same signatures being used to prove the Yucatan impact was a strike as well. Both articles present both pros and cons to the debate you failed to offer up.
  None of this pandering and wandering around the topic meets the question..why are no dinosaur remains found within a nine foot (3 meter) gape of the iridium analomy that supposedly caused their extinction. The answer is simple, the dinosaurs were mostly long gone prior to the impact and the fossil record proves it quite well and thoroughly. In his 1997 book, " Digging Dinosaurs" Horner stated, that in something like 15 seasons of excavations in the what you are suggesting as the PRIME location for finding dinosaur remains close to the kill event, he never once uncovered a single BONE within nine feet of the analomy. That is pretty intense evidence isnt it? You dont get to have the analomy preserved and then whine the fossils somehow vanished...sorry.
    Continuing this logic then, if the actual die-off had been ocurring much further back as the evidence show, you would not find many dinosaur fossils close to the kill event, precisely what the fossil record shows.  So perhaps if you were to adjust your chronology for the end of the dinosaur reign to some date more accurate than an unrelated impact event, you might actually find areas exposed that match the end period of their reign? Notice how this argument far more closely meets the known facts than speculating the work of an impacting agent as cause.
  "A combination of events may have collaborated to kill off the dinosaurs. It is possible that nether the impact alone nor the Indian eruptions on their own would have proven so lethal, but the one-two punch may have done the job. It is possible that more than one impact may have occurred. It has been suggested that the seismic activity initiated by the impact could have set off the Indian eruption, but the timing of those events is not yet well enough understood to tell, and some suggest the lava flows had already so severely damaged the dinosaur fauna that the impact was able to deliver the coup de grace."

   I am sorry, this is directly from Greg Paul's book and DOES state precisely what I said in almost identical words, it is right there in very simple elegant terms. The final line states, PRECISELY what I have said from the start of this wandering little narative, again stop mis-quoting me.
  All of these people are stating the current consensus blah blah blah, but do you honestly believe they sat and did a person by person questionaire for each paleo-expert before writing that little line in the book? This is precisely what was done in the book "Hunting Dinosaurs" and why I chose to quote and cite the book. The author interviews most of the known names in the paleo field and offers their thoughts. Rather than copping out and using the cliche.....the general consensus is...I gave you specific names and quotes, not a cliche.
It is a much more endearing method of making a point, despite the efforts to undermine it giving the incorrect title, print date and so forth.
   I did state summoning up, this act of creating a "ghost in the machine" as it were. "
Here is your quote from the author you cited..make note NONE of it disagrees with my own interpretation of the evidence. I myself stated the ongoing catastrophes were reducing oxygen content and eliminating plant life, I already made this point myself. As for just below the layer, I think it might have been a good idea to elaborate just how far below. I somewhat doubt it is quite as close as being implied.

On the biological side, paleobotanists have documented a radical decimation of plant life at the end-Cretaceous boundary. Just below the iridium layer, fossil pollen and spores from many locations around the world indicate a diverse flora. Immediately above this layer, the pollen and spore evidence is heavily dominated by a single type-- ferns. Ferns are one of the first plants to recover after major environmental catastrophes, and this "fern spike", as it's been called, is cited as evidence of a sudden cataclysm--that is, death by silver bullet."
  My information for crater sizes, impact sites and their dated occurrences was from information cited by Alvarez, and his sons, the authors of the impact theory. IF you use KNOWN impact Sites within the MESOZOIC period, the yucatan crater according to the study done by Alvarez places it in either fifth or sixth depending on Shiva and its status.
  I already debunked the rather silly comment about exposed sites for the late creataceous earlier. If we dated dinosaur extinction to the actual event and not an unrelated impact, you would find that many of the sites already availible are closer to the tail of the dinosaurian reign than previously understood.Remember, there is a NINE foot gap between the last found dinosaur fossil and the analomy. The single known instances of this being in variance are a single triceratops horn, shown in the paper Wings posted....(which is somewhat debate worthy in itself...those horns are supposed to come in pairs right?) And the findings above the K-pg level in the San Juan basin. Outside that NOTHING. NOTHING within nine feet of the boundary event at all. That is a LOT of geologic time to contend with isnt it?
    And please make note, the author you are quoting stated...."The fossil record of dinosaurs is remarkably sparse for the final stage of the Mesozoic. Indeed, to date, only one place on Earth--- the Hell Creek Formation exposed most abundantly in eastern Montana and Dakotas--- has been investigated in detail."

He is NOT saying the sites do not exist, he is stating they have not been investigated in detail. Again , please do not misquote .
  As for Nanotyrannus and Dracorex, the last I read they were under discussion and nothing had been determined for certain wether juvenile or different species . Perhaps we should leave it that way until science can offer proof rather than playing armchair scientist?  I did state size matters...these dinosaurs that are being mentioned from the Cretaceous have far less oyxgen needs than a 100 foot long sauropod for instance.... or did you wish to revise that as well?

                      "You claim no scientists subscribe to the "silver bullet" hypothesis. You also claim that the dinosaurs were obviously already in decline. Scott Sampson has this to say..."

I will request again very nicely, please refrain from misquoting me. I did NOT say what you posted. I said that the prevailing view is NOT that dinosaurs died by impact ....I never once stated there are NO scientists that subscribe to the hypothesis. I do not much care for character asassinations, and distortions, especially when connected to gross exaggerations of the worst and most inflammatory kind. I prefer you quote me at least somewhat accurately in the future PLEASE.  I did however state the dinosaurs were already in decline, but this is what the fossil record also shows, thanks.

I will address Mr Sampsons comments next.



        "For a long time, I regarded myself as a card carrying member of the gradualist-Blitzkrieg camp. However three lines of evidence have caused me to change my mind and join the ranks of the silver bullet enthusiasts. First is the documentation of many additional K-T boundary sites preserving that anomalous iridium layer; the presence of this asteroidal signature at far-flung locations around the globe confirms that the Chicxulub impact was truly a devastating, global event
   (The problem with the argument he is making here is the same signatures and findings could as easily be from the multiple impact scenario, and also as easily from another impact site as well. The sites in Russia, Silvertip and Shiva all carry matching Iridium signatures and disprove that the Chicxulub impact HAD to be the lone impacter.)
    Second is a growing fossil database indicating that the terminal Cretaceous world was not stressed to the breaking point, awaiting arrival of an extraterrestrial coup de grace. With regard to dinosaurs in particular, recent work in the Hell Creek Formation and nearby Lance Formation have documented a much more diverse fauna than previously realized. Certainly some dinosaur lineages (e.g., short-frilled ceratopsians and crested duck-bills) went extinct prior to the end of the Cretaceous, but overall dinosaur diversity remained relatively high, with many groups represented by truly gigantic exemplars such as Tyrannosaurus, Ankylosaurus and Pachycephalosaurus."

     (This argument actually makes itself. He is stating entire lines of dinosaurs disappeared and he does not find it entirely persuasive?What of the many types that are not mentioned here? There were ENTIRE families of dinosaurs gone prior to the end of the Cretaceous that left nothing behind for a desendant. The North American Sauropod for instance? )

"I see no grounds for arguing that dinosaurs (or other groups of animals or plants) were undergoing a slow, attritional demise in the latest Cretaceous. We must keep in mind however, that our knowledge of dinosaur diversity at the very end of the Cretaceous is limited to one place in western North America...Finally, it seems questionable to argue for a lethal cascade of agents when compelling evidence exists for a single agent capable of doing the job on its own."

   So he is stating, I see no evidence and accept that the impact did the job.But, it seems questionable to argue for a lethal cascade of agents? Questionable to whom? Since we know they exist and have found the sites? ummm...

Finally I took the time to google the two terms I have used, Deccan traps, and the Shiva crater, and am going to post the actual related information, so everyone can see the actual information , in its completeness to topic, rather than the altered versions previously posted.

First Shiva.......
The proposed Shiva crater and other possible impact craters along with the Chicxulub has led to the hypothesis that multiple impacts caused the massive extinction event at the end of the Cretaceous period. Chatterjee is confident that Shiva was one of many impacts, stating that "the K-T extinction was definitely a multiple-impact scenario." However, other scientists remain unconvinced that the extinction event was caused by multiple impacts, or that the Shiva feature is even in fact a crater. Other theories have argued that since the Chicxulub impact is believed by some researchers to have occurred earlier than the extinction of the dinosaurs, Shiva's impact was enough to cause the mass extinction by itself.






Unlike typical known extraterrestrial impact structures, Shiva is teardrop shaped, roughly 600 km × 400 km (370 mi × 250 mi). It is also unusually rectangular. Chatterjee argues that the low angle of an impact combined with boundary fault lines and unstable rock led to this unusual formation.Other researchers have noted that rock faults and impacts could modify the crater shape.[6] The crater also is reported to contain larger than average amounts of alkaline melt rocks, shocked quartz, and iron oxide laced with iridium. These types of rocks and features suggest an impact origin. The age of the crater is inferred from the Deccan traps, which contain relatively high amounts of iridium (an element extremely rare in the Earth's crust but more common in asteroids).






And the Deccan traps........

The Deccan Traps formed between 60 and 68 million years ago,[2] at the end of the Cretaceous period. The bulk of the volcanic eruption occurred at the Western Ghats (near Mumbai) some 65 million years ago. This series of eruptions may have lasted less than 30,000 years in total.[3]

The original area covered by the lava flows is estimated to have been as large as 1.5 million km², approximately half the size of modern India. The Deccan Traps region was reduced to its current size by erosion and plate tectonics; the present area of directly observable lava flows is around 512,000 km2 (197,684 sq mi).

]The release of volcanic gases, particularly sulfur dioxide, during the formation of the traps contributed to contemporary climate change. Data points to an average fall in temperature of 2 °C in this period.



Because of its magnitude, scientists formerly speculated that the gases released during the formation of the Deccan Traps played a role in the Cretaceous–Paleogene extinction event (also known as the K-Pg extinction), which included the extinction of the non-avian dinosaurs. ]Sudden cooling due to sulfurous volcanic gases released by the formation of the traps and localised gas concentrations may have contributed significantly to mass extinctions.
However, the current consensus among the scientific community is that the extinction was triggered by the Chicxulub impact event in Central America (which would have produced a sunlight-blocking dust cloud that killed much of the plant life and reduced global temperature, called an impact winter).[5]


As you can cleary see, both results were edited to only provide supporting data and all indications of what I had proposed were removed in a rather transparent effort to undermine my points.

[amargasaurus cazaui]

I did wish to request the admin make this discussion a seperate topic. I realized tonight I for one, am entirely guilty of totally hijacking gryphs thread on the Hadrosaurus, and he has not complained or made a rude comment despite that.  I apologize to you Gryph, and will wait till the thread is split before further comments, please return this topic to the intended subject.
   A possible title for the new thread might be...."We already have Chicken Little in our fairy tales, does he belong in our science? " thanks