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Re: New refs (long)

DinoBoyGraphics@aol.com wrote:

Itâ??s inconsistent, though, to use so many marine organisms as your examples of metabolic diversity, but then argue, â??no extant land mammal has ever achieved the dimensions of the largest sauropods - or even the largest hadrosaurs.â??

Not inconsistent at all. Are you seriously arguing that *every* dinosaur - from herrerasaurs to brachiosaurs to iguanodonts to microraptors to hummingbirds - adhere(d) to the same metabolism?

Ok, let me get this straightâ?¦arthropods and lamniforms are good dinosaur analogs, but placental mammals are a strawman?! I
think your comparative morph maybe a bit rusty.

I never argued that arthropods and lamniforms and good dinosaur analogs. My point was to refute your statement: "There is absolutely no support for this [i.e. variability in endothermy/ectothermy] amongst extant animal groups."

<Placental mammals represent a very limited (and very artificial) clade for comparison to dinosaurs. Would you say that _Coelophysis_ and _Brachiosaurus_ had the same metabolism as any modern bird? If you don't, then you're argument is already dead in the water. If you do, then you're on your own...>

Iâ??m really not sure what you mean by placental mammals being an artificial clade.

I mean your choice of the clade Placentalia as analogs to the Dinosauria is artificial. You nominate a clade (Placentalia) where the constituent taxa stay within fairly narrow metabilic confines, and then argue that because placentals do, then dinosaurs must have as well.

Why not expand your circle of mammal analogs to include non-placentals? Monotremes (as I said previously) have a different metablism to placental mammals; but apparently (says you) the metabolic diversity that exists within the Mammalia cannot be applied to dinosaurs. Your artificially limiting the comparison to between placentals and dinosaurs.

As for "reproductive styles". Again, you're implying that two clades can be compared directly. In this case Placentalia = Dinosauria. However, according to your argument, Mammalia > Dinosauria because the former exhibit three (at least) different types of reproduction, but dinosaurs only one. That won't wash, I'm afraid. Check out:


Surely you arenâ??t referring to the amount of morphological diversity? It far exceeds that of dinosaurs. There are no brachiating dinosaurs, no cetacean analogs, no sea otter analogs.

Now you're trying to do something very tricky: measure 'morphological diversity', and use it to justify comparing one clade to another. See above.

There is far more variety in niche exploitation and locomotive style in placentals than in dinosaurs.

Apples and oranges. See above.

I think the world would be a much better place if people could move away from the "endothermy vs ectothermy" and "warm-blooded vs cold-blooded" dichotomies.


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