Question...

I don't know about others, but I concider all tetrapods to be fish adapted for living on land. (Or even returned to water). And, possibly, all tetrapods AND fish as being weird-ass echinoderms.

Oh, but amphibians plus amniotes no longer equals tetrapods according to the strict cladists. Amphibia has two cladistic definitions: (1) the crown group definition (which is equivalent to Lissamphibia); and (2) everything more closely related to living amphibians than to amniotes. Either way, the cladistic definitions are much more restrictive than the traditional Amphibia (= non-amniote tetrapods), which Harshman was referring to. Only with the traditional paraphyletic Amphibia (which I still recognize, as do the majority of biologists) does amphibians plus amniotes equal tetrapods. If you don't believe me, see the Arizona 'Tree of Life' for a discussion of the strictly cladist viewpoints of Amphibia. Kind of pathetic that the strict cladists steal away a perfectly good name from us, and then they can't even agree among themselves which cladistic definition to use. Long-used paraphyletic groups like Amphibia, Reptilia, Dinosauria, etc., should NOT be turned into clade names. Dinosauria as a paraphyletic group for 'non-avian dinosaurs' is still in use in spite of strict cladists' attempts to humiliate the opposition or anyone who dares uses it in a paraphyletic sense. This is going to eventually create a backlash, most people will still think of birds as a separate class of 'dinosaur descendants', and it will be the strict cladists who are humiliated into admitting it was just a matter of semantics all along. But by then, the reputation of really useful cladistic 'analysis' will suffer from its association with strictly cladistic 'classification'. And that is a shame. The notion that paraphyly is unnatural is semantic sophistry, and on that one point, I can certainly agree with Feduccia. Strict cladism created a climate which produced the ABSRDists. Strict cladism is one extreme and strict eclecticism (ABSRDism) is the opposite extreme. Limited paraphyly is the only logical response to these two extremes, and that is what I advocate. So to answer the original question, separating Class Aves from a paraphyletic Class Reptilia (incl. a paraphyletic Dinosauria) is perfectly natural, and is therefore a division that is likely to survive the 'Strict Cladism Era' of the late 20th Century. And it is admittedly arbitrary where you draw the line, but that is true of all classifications (whether strict cladists want to admit it or not).

And also realize that, other than shock value, there is no point to calling your parakeet a dinosaur. After all, if one is gong to do that, then you might as well say:

'Hey look at my feathered bacterium'

Though, admittedly, that last one might be worth it for a few odd looks

This little paragraph encapsulates what, to me, is the coolest thing about cladistic classification. It screams 'evolution' to know that we're all just a bunch of weird Sarcopterygii. And of course that birds are odd little theropods that fly. *************************************************** John, This is the problem. A very vocal minority of biologists (strict cladists) have been 'screaming' for 30 years that classification MUST be based on phylogeny alone. If the rest of us want to reflect some divergence information (paraphyly) in classifications, strict cladists 'scream' that they are unnatural, and that we are too stubborn, stupid or lazy to realize it. I hate to burst your bubble, but this kind of uppity 'Ivory Tower' elitism is a bunch of crap, and eclecticists are sick and tired of it. And if you think we are slowly dying off, you'd better think again. Many younger workers are now rejecting strict cladism, and a whole new trend is developing that will result in a cladisto-eclectic synthesis. This may not be clear now, but it will be ten years from now. And I obviously do NOT conflate cladistic 'analysis' with strictly cladistic 'classification'. However many people do conflate them, so I fear that the coming backlash (against strictly cladistic classification methods) will unfortunately also hurt the reputation of cladistic 'analysis' as well. One of my main goals is to prevent the backlash from going that far. Calling birds 'dinosaur descendants' gets across the same evolutionary message as does screaming that 'birds ARE dinosaurs'. Likewise, tetrapods are 'sarcopterygian descendants', but that doesn't mean we have to classify them as Sarcopterygii. The rest of us see this as simplistic sophistry that is highly irritating, and pretty soon it will be the younger generation of biologists who is waiting for the strict cladists to die off.

I suggest you take a course on phylogenetics and especially cladistic analysis. You do not seem to understand the simple concept of a monophyletic group.

There is a very important point to it. There is no significant biological reason *not* to call your parakeet a dinosaur, any more than there is one to not call your dog a mammal. Do you think that calling your dog a mammal would be pointless except for the 'shock value'?

Not really, unless you define 'bacteria' as a clade including the Metazoa, which would be very difficult to do considering that lateral gene transfer and thus clade-crossing is rampant among unicellular organisms.

(I'm not very up on bacteriology or microbiology, but for myself, I find it a waste of time and energy to try to define any clades outside the Metazoa, Fungi, and Viridiplantae, since the widespread lateral gene transfer and endosymbiosis outside those 3 groups makes defining relationships a lot more nonlinear. The only clade outside those that I accept as almost certainly truly monophyletic is the entire clade of Life itself.)

It would be correct, however, to say 'look at my feathered romeriid/amniote/tetrapod/osteichthyan/vertebrate/ crainate/chordate/ deuterostome'. But those are less useful because they are so broad as to include a vast number of different possible pets. 'Dinosaur' is narrow enough that only birds get the title. Also, wider groupings are so broad that they include animals of all different niches and ecological roles (ranging, for example, from tunicates to tyrannosaurs within the Chordata), whereas 'dinosaur' is narrow enough that it is a real, significant grouping not only evolutionarily speaking, but also ecologically and anatomically speaking. If you were a time-traveling alien visitor observing the history of life on Earth, you would see such incredible similarities between birds and nonavian dinosaurs as compared to the similarities between either and any other group, that you wouldn't even consider the idea of *not* including them together in one taxon, any more than you would consider the idea of not including frogs and salamanders together in on etaxon (what we call the Amphibia).

Sure, 'some question', as there is 'some question' over the belief that the known Universe is expanding. In both cases, there are a couple of fringe members who continue to claim the view is wrong, but the overwhelming majority of physical evidence supports the view to the point that it would necessitate a *tremendous* flood of completely new evidence contradicting it to make the idea of rejecting it even remotely tenable within the framework of science.

Because the clade Dinosauria includes the Aves, while the clade Amphibia does not include the Reptilia. If you were to arrange the tree linearly, moving 'forward' from fish to birds, amphibians would be a unique sidegroup branching off before the reptiles, whereas dinosaurs would be the entire tip of the tree and a lot of side branches with it. It's not a question of semantics, it's a question of

That's not exactly the same thing. If you want a valid comparison then it would be like calling my dog a therapsid, which *is* pointless.

I'd go so far as to call it a 'feathered archaean,' but apparently there is some debate as to exactly how 'antique' archaea is. I went with bacteria, as it seems to be more generally accepted as being the 'basement' of all other life. It's a sweeping generalization, but at least it's a rather stable one.

If you would like more stability, I suppose I could have said that it was a 'feathered prokaryote.' Now I have heard arguments in favour of Eukaryota being the more archaic/basal group for life, but for now most of the evidence still seems to indicate Prokaryota, so I'll stick with that for now.

And ceratopians, sauropods, ornithopods, ankylosaurs, prosauropods and possibly even pterosaurs and chelonians, depending on the time of the week and the position of the planets. >

Compared to Aves? Dinosauria includes bipedal and quadrupedal animals, ranging in size from little 10 lb buggers to 100+ tonne animals. They had armoured creatures with clubbed tails, horned animals, sharp toothed critters, runners, hobblers and everything inbetween.

Aves, on the other hand, has animals varying from a little over a gram, to just under half a tonne. All were feathered, most were tailess, and all retain only slight variations on what is essentially, one bodyplan.

It would appear to me that 'Avian', is much more apt, than 'Dinosaurian.'

I think that you might be exaggerating the similarities between birds and a small set of dinosaurs (mostly members of maniraptora) a little.

The similarities between a neornithine and a sauropod are very few and far between (without getting into things shared with other tetrapods/vertebrates/chordates etc.). Hell, even the most staunch 'birds are dinosaurs' supporter admits that there is a huge gap between neornithines and the closest theropod relative. Most dino similarities are seen in earlier birds, especially those that are straddling the line between Aves and Dinosauria. These animals also share most of their similarities with dinosaurs closest to them, while the rest of Dnosauria doesn't look even remotely Avian like.

If I were an alien viewing the progression of life, and I was going to assign creatures to different taxa, I'd probably keep most of dinosauria nearer to Reptilia, than Aves. They would probably be nearest to crocs, but also very near to Lepidosaurs. Sebecid and Pristichampsid crocodyliformes would be placed nearer to dinosaurs than to other crocodyliformes, and I'd probably wind up placing salamanders near the base of Lepidosauria.

Of course, this is assuming that I'm just giving a cursorial view of this life.