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Re: Physiological Adaptations of the Dinosauria

From: Waylon Rowley>Subject: Re: Physiological Adaptations of the To: Dr Timothy J. Williams Subject: Physiological Adaptations of the Dinosauria

From micropaleontologist Michael J. Styzen: "Virtually all the genera of both planktonic foramanifera and calcareous nannoplankton were wiped out at the same time as the dinosaurs. Between those two groups you carve out a pretty hefty chunk of the Earth's biomass. A lot of other marine organisms suffered a similar fate. If you take a close look at most groups of non dino terrestrial organisms you will find out that hardly any groups just sailed on through the K/T boundary unscathed. Unless you can convince me that some disease agent can affect dinosaurs, marine golden brown algae, sarcodinid protists (forams), ammonites and a host of other things I really can't take the disease hypothesis seriously."

That's very interesting....but I fail to see how it applies to my hypothesis. I'm not debating the fact that major ecological changes occured (e.g. a monster bolide impact), i'm trying to show how ornithodirans were *more* susceptible to these changes than mammals, birds, and many other small vertebrates. Another HP on this list agreed that at first the iridium cloud would have cooled the earth, then heated it. I'm not a marine invertebrate biologist, but rapid temperature increases like that would dramatically effect plankton, including a host of other organisms higher up on the trophic levels that relied on them as a food source. If the stored heat in the worlds oceans were to transfer to a cold atmosphere after a meteor impact, I can guarantee
these little guys would drop like flies..err..plankton.

I think you may have misunderstood me. There are NO Mesozoic bird specimens that show RT's. Nil, naught, zero, zippo. RT's are cartilaginous and so aren't fossilized. If they did have them, we wouldn't know about them. This applies to dinosaurs too. Unless the RT's are ossified, we are not likely to find them in fossil bird/dinosaur/mammal/pterosaur taxa. They may have had RT's, they may have not. We'll probably never know. And nobody except Ruben seems to care.

Let's not forget little Scipionyx. I totally disagree that we wouldn't know about them if they existed. RT's have well-defined ossified attachment ridges on the nasal bones. A very well preserved skull of a theropod should show evidence of these structures. So far, only the crushed olfactory turbinates are known in Nanotyrannus lancensis (juvenile T. rex?) which suggests that the equally fragile RT's CAN be identified.

Some probably were, but by no means all. By the end of the Cretaceous, placentals/eutherians were VERY diverse, both ecologically and morphologically. OK, they were all small (the largest were cat-sized), but modern-day rodents and insectivores occupy a wonderfully diverse array of niches.

Do you think that mammals would survive fairly large temperature swings?
Their RT's are cooled up inhalation (birds as well), but my proposed dinosaur fossa had to rely on ambient air temperature.

Multituberculates actually survived beyond the Cretaceous extinction. They didn't become extinct until well into the Tertiary, and didn't begin to decline until the Eocene.

Okies. :)

Yes, they may have. Then again, they may not have. Nobody knows. It doesn't support your hypothesis either way.

Well, I know my basic hypothesis works because I made a crude model of a theropod skull with tubing, polystyrene, and some other materials that showed clear condensation on the walls of the reconstructed chamber.
The experiment (I admit) was pretty pathetic, but that's precisely why someone should do isotope studies of dinosaur skulls to try and confirm it.

I'd say that if frogs were so resilient to environmental change at the K/T, why are they so sensitive to environmental change at the current time.

Maybe because the environmental changes are different this time? Both are ectotherms, so I don't think they would suffer much from a global increase in temperature. Besides, they could both take advantage of their aquatic habitat to cool off.

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