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Definition of "Aves"?
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How should "Aves" be defined?
As a crown group (e.g., sensu Gauthier 1986)
23%
 23%  [ 3 ]
As a total group (e.g., sensu Ax)
0%
 0%  [ 0 ]
As a non-crown node-based clade (e.g., sensu Chiappe 1997, Sereno 1997)
30%
 30%  [ 4 ]
As a non-total branch-based clade (e.g., sensu Marjanovic [unpublished])
30%
 30%  [ 4 ]
As an apomorphy-based clade (please specify).
15%
 15%  [ 2 ]
Other (please explain).
0%
 0%  [ 0 ]
Total Votes : 13

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tmkeesey
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PostPosted: Mon 02 Oct, 2006 7:18 am    Post subject: Reply with quote

Nescio wrote:
What is David's list of external specifiers?

I came across the abstracts for this past summer's ISPN meeting while cleaning today. Marjanovic's definition of Aves is branch-based with Passer domesticus internal and Velociraptor mongoliensis, Oviraptor mongoliensis, Segnosaurus galbinensis, Troodon formosus, Sinornithoides youngi, Ornithomimus velox, Tyrannosaurus rex, Compsognathus longipes, Ornitholestes hermanni, Coelurus fragilis, Coelophysis bauri, Hypsilophodon foxii, Crocodylus niloticus, Sphenosuchus acutus, Euparkeria capensis, Megalancosaurus preonensis, and Sorex araneus external.

As you can see he's safeguarded it against all hypotheses, no matter how outdated or poorly supported. Personally, I think the list of external specifiers could be trimmed down a bit (perhaps even to just the first five minus S. galbinensis), but it doesn't matter all that much.

(Incidentally, the reason there are two troodontids in the list is because the type specimen of Troodon formosus is a tooth, so it may be a nomen dubium, although it's usually synonymized with the well-known Stenonychosaurus inequalis these days.)
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David Marjanović



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PostPosted: Tue 03 Oct, 2006 8:46 pm    Post subject: Reply with quote

Thanks for digging this up! Smile

I agree that people, if forced to make the choice, would rather have Archie out than Deinonychus in; that's why I used Velociraptor as an external anchor and didn't mention Archaeopteryx. Of course, under most published phylogenetic hypotheses Archie would be inside and Deinonychus outside, so the traditional contents would be preserved precisely.
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Eoraptor



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PostPosted: Thu 05 Oct, 2006 1:07 pm    Post subject: Reply with quote

Quote:
came across the abstracts for this past summer's ISPN meeting while cleaning today. Marjanovic's definition of Aves is branch-based with Passer domesticus internal and Velociraptor mongoliensis, Oviraptor mongoliensis, Segnosaurus galbinensis, Troodon formosus, Sinornithoides youngi, Ornithomimus velox, Tyrannosaurus rex, Compsognathus longipes, Ornitholestes hermanni, Coelurus fragilis, Coelophysis bauri, Hypsilophodon foxii, Crocodylus niloticus, Sphenosuchus acutus, Euparkeria capensis, Megalancosaurus preonensis, and Sorex araneus external.

As you can see he's safeguarded it against all hypotheses, no matter how outdated or poorly supported.


I don't see Longisquama in the list! Wink
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ottscay



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PostPosted: Thu 05 Oct, 2006 5:14 pm    Post subject: Re: Apomorphy-based Aves Reply with quote

kinman wrote:

Therefore, I would predict that David's definition will be rejected by most workers if it fails to include Archaeopteryx as an internal specifier.


I think it should be completely inadmissable to include Archaeopteryx as any kind of specifier for Aves. There are many legitimate lines of arguement that suggest it couldn't fly well, if at all (sorry guys, but there are, even if it isn't the majority opinion). Since we know that maniraptorans in general were winged (but not neccesarily primatively flying) it's an inexcusable example of letting the tradition tail (Archaeopterys is the "first bird") wag the theoretical dog. Look, Archaeopteryx could well be a deinonychosaur exclusive of all other birds, and I could make a case (and may yet) that it's a basal troodontid and that birds are closer to dromaeosaurs, in which case there is no reason to include Archaeopteryx, especially if birds did not inherit flight from it. David's definition allows for eventualites like these.

It's specifically because of the instability of Paraves that we need to allow Archaeopteryx to float into and out of Aves as the evidence dictates.
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leowsham



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PostPosted: Thu 05 Oct, 2006 5:18 pm    Post subject: Reply with quote

Eoraptor wrote:
I don't see Longisquama in the list!

Nor any particular pterosaurs e.g. Sordes pilosus... Rolling Eyes Though, I think going as far as Coelurus is quite enough. It's good to be prudent, but one has got to make his stance... this echoes much with the case of Orbitoscuta (in the other thread): you just can't play to the gallery each and every time!
And I don't see the PhyloCode recommend anything as per David's style here (no personal offense Exclamation )
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tmkeesey
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PostPosted: Thu 05 Oct, 2006 7:18 pm    Post subject: Reply with quote

leowsham wrote:
And I don't see the PhyloCode recommend anything as per David's style here (no personal offense Exclamation )


From Note 9.4.1:

Quote:
A branch-based definition may take the form "the clade consisting of A and all organisms or species that share a more recent common ancestor with A than with Z" (or Y or X, etc., as needed) or "the most inclusive clade containing A but not Z" (or Y or X, etc.).


As you can see, multiple external specifiers (Z, Y, X) are perfectly permissible. (So are multiple internal specifiers, if the definition is intended to be potentially self-destructing; see Art. 11.8 Example 3.)
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David Marjanović



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PostPosted: Thu 05 Oct, 2006 8:08 pm    Post subject: Reply with quote

I really forgot Longisquama! Shocked Thanks for reminding me! I don't think anyone has proposed pterosaurs in the primary literature in the last 100 years or more, though.

If Archie is a troodontid, nomenclature gets interesting. The ICZN would require the replacement of Troodontidae by Archaeopterygidae. I wonder if anyone would write a petition for the conservation of Troodontidae... or if it would make any people prefer the PhyloCode where this kind of problem does not exist. Cool
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kinman



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PostPosted: Fri 06 Oct, 2006 3:08 am    Post subject: Apomorphy-based AVES Reply with quote

Well, if Troodontidae and Archaeopterygidae form an exclusive clade, I would probably favor keeping them as separate sister families. But I also wouldn't be strongly opposed to sinking Troodontidae as a synonym of Archaeopterygidae.

But frankly I think it more likely that Archaeopterygidae will clade with some family of dromaeosaur (and I still favor splitting dromaeosaurs into more than a single family). Whether Archaeopteryx flew well or only flew poorly doesn't matter much to me. It had the wings of a bird and has been traditionally regarded as a bird. Furthermore, various dromaeosaurs also flew (whether well or poorly or lost flight altogether), they sat on nests incubating ornithoid eggs, and would have lived lives similar to Tertiary birds (whether flighted or flightless).

Some of the large flightless birds of the early Tertiary didn't lead lives terribly different from flightless dromaeosaurs (except the latter still had teeth and longer tails). The loss of teeth and reduction of longer tails probably happened several times independently, so those aren't all that significant in the larger scheme of things. Forms like Microraptor should not be excluded from AVES just because they were discovered so late in the game. It almost certainly flew, nested on ornithoid eggs, and was birdlike in many other ways. I see no good reason to exclude forms like Archaeopteryx and Microraptor from AVES, and I still predict that most workers will still balk at excluding Archaeopteryx in particular. I think even many Phylocodists realize that excluding Archaeopteryx and alienating traditionalists (who mostly follow the ICZN) is counterproductive. AVES is a traditional taxon, and Phylocodists should take EVERY opportunity to avoid antagonizing the non-Phylocodists (and remember that even many strict cladists don't like PhyloCode either). Pick your battles carefully or risk being marginalized and eventually defeated altogether. You're skating on very thin ice on this one, and ignoring non-Phylocodist strict cladists as well as non-strict-cladist traditionalists may be more harmful to cladism than you ever imagined. If so, don't be surprised if even more strict cladists actually join in the criticism of PhyloCode. You are painting yourselves into a very small corner on this one, and if you can't recognize that, I can only say that you were warned. You reap what you sow, so continue in your uncomprising positions, and you deserve what will eventually happen to PhyloCode.
----Ken Kinman
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David Marjanović



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PostPosted: Fri 06 Oct, 2006 3:37 pm    Post subject: Reply with quote

kinman wrote:
The loss of teeth and reduction of longer tails probably happened several times independently, so those aren't all that significant in the larger scheme of things.


Loss of teeth: obviously. Tail reduction: not as far as known today (Sapeornis, Confuciusornithidae, and Ornithothoraces form a clade to which nothing long-tailed belongs).

But more importantly, why are you so agitated? Confused Firstly, I am not the PhyloCode, nor am I the editorial committee of the Companion Volume; so if you don't like the definition I propose, there isn't the slightest reason to despair. Secondly, under most published phylogenetic hypotheses, Aves as I want to define it would include Archaeopteryx and exclude all traditional non-birds such as Dromaeosauridae; surely that's a good thing! Thirdly, if Exclamation forced to choose between having both of them (Archie and the dromies) inside or both of them outside, I'd rather have both outside than having things like Achillobator inside. I think this will be easier to accept for more people than the alternative (having both inside); but if you like that better, then let's simply publish, both of us, and then let's see where the discussion moves. Smile

Oh, and the ornithoid eggshell... if you use that as a defining apomorphy, you get the oviraptorosaurs in, and that means you get the segnosaurs. If you really want Therizinosaurus to be a bird, go ahead... I just doubt that you want that.


Last edited by David Marjanović on Fri 06 Oct, 2006 3:44 pm; edited 1 time in total
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PostPosted: Fri 06 Oct, 2006 3:42 pm    Post subject: Reply with quote

kinman wrote:
You're skating on very thin ice on this one, and ignoring non-Phylocodist strict cladists as well as non-strict-cladist traditionalists may be more harmful to cladism than you ever imagined.


To cladism?!? To phylogenetic nomenclature, yes, but not to cladistics! Confused

Besides, I think I'll state it bluntly: I haven't seen anyone yet who dislikes either cladistics or phylogenetic nomenclature or both but has actually understood them. Mind you, this is to no small part a failure on our side, not on theirs, because we have failed to explain them well enough in enough literature that reaches everyone.
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Nescio



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PostPosted: Fri 06 Oct, 2006 7:32 pm    Post subject: Reply with quote

David Marjanović wrote:

Oh, and the ornithoid eggshell... if you use that as a defining apomorphy, you get the oviraptorosaurs in, and that means you get the segnosaurs. If you really want Therizinosaurus to be a bird, go ahead... I just doubt that you want that.

Well, confronted with reconstructions like this one, I think I could live with Therizinosaurus as a bird:



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kinman



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PostPosted: Sun 08 Oct, 2006 1:09 am    Post subject: Apomorphy-based AVES Reply with quote

Ah, but therizinosaurs have a non-ornithoid eggshell microstructure that is nothing like eggshells of oviraptorosaurs. One of many reasons that I have always disputed the enigmosaur "clade". I still believe that therizinosaurs split off between ornithomimosaurs and my expanded AVES (including deinonychosaurs and oviraptorosaurs and mononychiforms). Oviraptorosaurs are probably more derived than deinonychosaurs, so I would also object to using any oviraptorosaur as an external specifier. Anyway, so-called wide-accepted phylogenies are likely to be less widely accepted in the future. Be ready to throw them and enigmosauria on the trash heap with Bullatosauria and Arctometatarsalia. By the way, I do use cladistics and considered myself a cladist. However, I do believe strictly cladistic nomenclature (and PhyloCode in particular) has given a black eye to cladistics in general. My main goal is to minimize that harm, particularly as it concerns traditional taxa like Aves, Mammalia, Reptilia, Amphibia, etc.
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leowsham



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PostPosted: Sun 08 Oct, 2006 1:58 am    Post subject: Reply with quote

Nescio wrote:
Well, confronted with reconstructions like this one [as shown above], I think I could live with Therizinosaurus as a bird

I know that a paleoartist does not equate to a paleontologist, but being one, I could say that nowadays it is politically sensible Exclamation if not simply tres chic to put some downy "coat" (at least) on something suposedly, eh, more related to "birds" than to "traditional theropods". I wouldn't say we're subconsciously being our own judge on phylogenetic analysis, and feather is certainly not the sole watershed for birdiness, but you see the point is made - if therizinosaurs were determined to be within Aves... not much nausea indeed (when at least Archie is in).
BTW, the present battlefront is still on tyrannosaurids. Ask anyone and you'd still found quite a bunch who'd balk at the idea of a birdy tyrant. Strangely though, if compsies were indeed more basal, this would appear more like some relic of carnosaur-nostalgia than true science.
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PostPosted: Sun 08 Oct, 2006 12:30 pm    Post subject: Re: Apomorphy-based AVES Reply with quote

kinman wrote:
Ah, but therizinosaurs have a non-ornithoid eggshell microstructure that is nothing like eggshells of oviraptorosaurs. One of many reasons that I have always disputed the enigmosaur "clade". I still believe that therizinosaurs split off between ornithomimosaurs and my expanded AVES (including deinonychosaurs and oviraptorosaurs and mononychiforms).


What you or I believe is not the only matter -- the matter is everything that is halfway plausible. Based on current data, it is possible that oviraptorosaurs and segnosaurs are sister-groups, so we must provide for that eventuality. I agree with you that surprises can always happen; if we want stability in nomenclature, we must try to create definitions that contain the same terminal taxa no matter what the phylogeny looks like. My proposed bird definition is an example of this: under any phylogeny proposed in the last couple of decades it has almost exactly the same contents. If you can do better still, do go ahead.

Quote:
Oviraptorosaurs are probably more derived than deinonychosaurs, so I would also object to using any oviraptorosaur as an external specifier.


Why do you insist on having dromaeosaurs as birds? I can't imagine that a majority of anything agrees with you on this.

Quote:
However, I do believe strictly cladistic nomenclature


There is no such thing as "cladistic nomenclature". This is a contradiction in itself. Cladistics is the method to reconstruct phylogenetic trees, not a method to put labels on them. Phylogenetic nomenclature, on the other hand, is a method to tie labels to defined places on trees, no matter how those trees were found.

Quote:
has given a black eye to cladistics in general.


Outside of Cave Bear Land ( = the paleontology institute over here), conodont phylogeny, and linguistics, cladistics has won thoroughly. There is no reason to be pessimistic -- it's over.

Quote:
My main goal is to minimize that harm, particularly as it concerns traditional taxa like Aves, Mammalia, Reptilia, Amphibia, etc.


I agree. This is why I want to publish a definition of Reptilia that effectively removes it from circulation, and one of Aves that keeps its traditional members in and its traditional non-members out, despite the possible sacrifice of Archaeopteryx.

Oh, yeah, and... have you published Mononychiformes, or why don't you use Alvarezsauridae/Alvarezsauria, and why doesn't it have a k like Mononykus the non-beetle does? Just wondering.


Last edited by David Marjanović on Sun 08 Oct, 2006 7:50 pm; edited 1 time in total
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tmkeesey
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PostPosted: Sun 08 Oct, 2006 5:11 pm    Post subject: Re: Apomorphy-based AVES Reply with quote

David Marjanović wrote:
There is no such thing as "cladistic nomenclature".


Presumably "cladistic nomenclature" = "nomenclature wherein only clades are named".

The PhyloCode advocates phylogenetic nomenclature, where taxa have to have a phylogenetic basis. This doesn't necessarily mean that they have to be clades (they could be species, for example). But the current draft does cover only clades, leaving species to the "traditional" codes.
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