* * * * CURRENT UPDATE * * * * There was a big article in today's Washington Post, saying that the K-T Extinction is now officially a done deal. Kirk R. Johnson of the Denver Museum of Nature and a team of "45 renowned scientists from an array of disciplines" sorted through all the evidence and deduced that "the crater really is the culprit." Their findings are in the current issue of "Science." The multiple-impact theory was based on the existence of several distinct layers of comet debris and evidence that many species survived the initial impact only to go extinct later. The team concluded that "those anomalies were created by jumbling of strata when debris flowed back into the crater after the impact." Apparently a competing hypothesis asserted that volcanoes in India had caused the extinction, but there should have been events in the biological world associated with that, and none were found.
Is this independant of the Cambridge article? I was never really a fan of the Deccan Traps hypothesis, I always thought they were pushing it to account for the Iridium (not my only objection, mind).
Don't know. Haven't really been following the controversy. Just thought you guys might be interested.
Fraggle, Trippy is politely pointing out that you've linked to another newpaper's story about the same paper outlined by the University of Cambridge in his initial post. From the OP:
Actually, I was genuinely seeking clarification, they've come to the same conclusion, but I was (and am) trying to establish whether or not there were two independent parties working on the same thing. The article I linked to in the OP from cambridge mentioned 41 scientests, where Fraggles mentions 45, although I seem to recall both talking about publishing in Nature (I think?). The only thing that I've beeen able to find out for sure is that this particular area of work is something of a specialty for Jonson - he seems to specialize in (I think) floral assemblages across the K-Pg boundary, and I've seen mention of his intention to do this wokr since, I think '07-'08
Both articles are talking about the same paper, though it appears that Cambridge has the correct number of scientists. The most extensive article I've yet found, http://www.sciencedaily.com/releases/2010/03/100304142242.htm Oh happy day, it has a phonetic pronunciation for Chicxulub (pronounced chick-shoo-loob)! I've always wondered how to say that.
And Wikipedia explains why cretaceous tertiary is abbreviated KT: http://en.wikipedia.org/wiki/Cretaceous–Tertiary_extinction_event I had a suspicion that Germans were involved. Just as we refer to lysergic acid as LSD because the German word for acid is saure.
Trippy: I've long puzzled over what it was about the dinosaurs that did them in compared to the other vertebrates. What if any is the major distinction that caused their extinction following the KT triggering event? One of the ideas I've tossed around was their egg-laying habit. Birds had taken to having their nests protected in trees, etc. where they were safer from predation. Turtles, etc. buried their eggs. So too the crocodilians. I don't know about the other marine reptiles - were they egg laying or had they evolved live-birth like some of the sharks? In any event, I believe the dinosaurs were making nests on the ground. As long as the mammals were in check, the predation wasn't too great. But once the large carnivorous dinosaurs met their demise, the mammal predation of ground nest eggs might have become intense, leading to the demise of all other such dinosaurs in a few centuries to millenia. What are your thoughts?
X in Nahuatl (the language of the Aztecs) is pronounced SH. However, since that phoneme does not exist in Spanish, it's colloquially pronounced in Mesoamerican place names either like Spanish J (German CH) as in Oaxaca and México, or like S as in Taxco and Mixtec. Even if it wasn't caused directly by predation, endothermic animals, having a greater energy source, are stronger and more intelligent than exothermic animals of comparable size. Look at how marine mammals, and even marine birds, are so often the apex predators in aquatic ecosystems even though they can't breathe underwater. A shark hasn't got a prayer in a fight against a dolphin--much less a whole pod of them, since their more complex brains evolved the pack-social instinct. (Fish who travel in groups are generally herd-social.) Even the adorable little penguins are the scourge of the seas from the perspective of the fish, with their wings fully transformed into fins and their endothermically powered musculature propelling them at incredible speed. I'm sure the mammals simply out-competed the reptiles. The surviving giant reptiles live in isolated ecosystems where there are no mammalian or avian predators to fend off. Except snakes, who have found a way to compete successfully. There are always a few species who stumble onto an evolutionary path that works for them.Please Register or Log in to view the hidden image!
One obvious factor: the big land animals died. More of the dinosaurs were big land animals, and more of the big land animals were dinosaurs. The little dinos did not all die, and we see them flying around even now. And the little other guys made it, some of them, as well - which evened things out more, in the next evolutionary run.
As I believe I have already suggested, when considering land animals at least (well, at least as I understand it), those that had the highest survival rates tended to be those that lived in lotic, estuarine, or marshland environments (presumably lacustrine/lentic as well), they also tended to be in food webs that were not dependent on primary production (eg photosynthesis), with sources of organic carbon including detritus and carrion (those that depended on dead plants and dead animals tended to survive), or insectivorous (yes, evidence suggests insect diversity was affected, however, insects did survive), they also tended to be those species that deposited their eggs (or young) in sheltered environments, or were capable of seeking shelter.
Larger animals need a much higher caloric and overall food intake to live. They die first. No different than the demise of the large land mammals on the North American continent around ~13,000 years ago in a probable NEO impact event. Short Faced Bear, the largest known mammal land predator ever, gone. The Dire Wolf, a really big wolf, gone. Saber Tooth Tiger, Mammoth, etc, gone. The large animals put themselves on a precipice due to the amount of food and water they need to stay alive. The long run of the dinosaurs had resulted in many large species, it was their advantage for millions of years, an evolutionary 'arms race' you might say, and it was their demise when food was scarce. Also some of the other details already mentioned came into play. BTW sharks kill and eat dolphins, this has been directly observed. Dolphins are rehabbed from shark bite injuries in our marine nursery programs. Something I saw earlier in the thread said otherwise erroneously.
Some of the reluctance to accept the KT boundary catastrophe theory is a mystical belief that nature is never a terrorist. It is better to face the actual nature of the cosmos so that we may have an adult view of things.
That was me. Is this fight between a shark and a dolphin of the same size? No dolphin species is an apex predator; there's always somebody bigger. Except maybe the orca; being pack-social and not having to take on a great white alone might give them an advantage. Sure, but is he telling all his friends, "You should see what I did to the shark!"
I was not referring to a single event. While I understood your point... in that dolphins have been observed running sharks off form humans by group attack, including after the shark had bitten a human and the dolphins ran the shark off and brought the human to shore. Amazing stuff that blows my mind. Dolphins have been observed attacking sharks and running them off no doubt. They will kill smaller sharks. But... I was just clarifying the point. Great Whites will kill and eat dolphins, as well as other sharks that will attack and try to eat them. It is not only the large sharks that do this, some of the more aggressive sharks are not the large ones. Please Register or Log in to view the hidden image!
