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Nick Gardner
Joined: 20 Aug 2006
Posts: 31
Location: VA
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 Posted: Fri 25 Aug, 2006 1:07 pm Post subject: |
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| tmkeesey wrote: | | David Marjanović wrote: | | Is there more than one font in this forum? That would explain it very easily. |
That would make the character show up as a block or a question mark, not as an HTML entity. It's almost certainly more complicated than that.
We're just using the phpBB default settings, so... |
Perhaps David entered the "HTML entity" himself expecting it would display as "ć", and that's why it isn't coming up.  |
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David Marjanović
Joined: 24 Aug 2006
Posts: 137
Location: currently Paris
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| Posted: Fri 25 Aug, 2006 9:05 pm Post subject: |
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No, I copied and pasted from the character table of Windows. I don't know any such HTML codes by heart.
Whatever. At least I'm recognizable! |
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Nick Gardner
Joined: 20 Aug 2006
Posts: 31
Location: VA
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| Posted: Sun 27 Aug, 2006 2:54 am Post subject: |
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| David Marjanović wrote: | No, I copied and pasted from the character table of Windows. I don't know any such HTML codes by heart.
Whatever. At least I'm recognizable! |
Better than myself, I suppose. |
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dinoguy2
Joined: 22 Aug 2006
Posts: 41
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| Posted: Fri 01 Sep, 2006 6:09 pm Post subject: |
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| Quote: | | I can't think of even just one apomorphy that would reliably diagnose such a clade. |
What's wrong with the pennaceous feather? This has been the only single characteristic completely unique to birds since Linneaus. |
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tmkeesey
Site Admin
Joined: 14 Aug 2006
Posts: 287
Location: Los Angeles, CA, USA
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| Posted: Fri 01 Sep, 2006 6:17 pm Post subject: |
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Which part of the pennaceous feather? The rachis? The barbs? The barbules? All three diagnose different clades.
More to the point, etymologically Aves does not refer to any characters but to a gestalt, a general concept. You might as well create apomorphy-based definitions for Theria or Felidae.
In other words, the only character specified by the name Aves is "birdiness".
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T. Michael Keesey
Director of Technology, Exopolis, Inc. |
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David Marjanović
Joined: 24 Aug 2006
Posts: 137
Location: currently Paris
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| Posted: Fri 01 Sep, 2006 10:28 pm Post subject: |
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| dinoguy2 wrote: | | Quote: | | I can't think of even just one apomorphy that would reliably diagnose such a clade. |
What's wrong with the pennaceous feather? This has been the only single characteristic completely unique to birds since Linneaus. |
Then why are you calling yourself "dinoguy"? Even if you mean that all parts of the pennaceous feather must be present, you still get a good chance of having Achillobator as a bird, because Microraptor has pennaceous -- even asymmetric -- feathers. Do you really want that?
With the present ignorance over eumaniraptoran phylogeny, the traditional concept of Aves is best saved by a stem-based definition (as I've proposed at both meetings, but never published): everything closer to Passer domesticus than to dromaeosaurs, troodontids, oviraptorosaurs, segnosaurs, and so on. And even this runs the risk of losing Archaeopteryx (hey, there's a nonzero chance that old Archie is the basalmost known troodontid or "dromaeosaur", for example). |
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tmkeesey
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Joined: 14 Aug 2006
Posts: 287
Location: Los Angeles, CA, USA
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| Posted: Fri 01 Sep, 2006 10:40 pm Post subject: |
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| David Marjanović wrote: | | Even if you mean that all parts of the pennaceous feather must be present, you still get a good chance of having Achillobator as a bird, because Microraptor has pennaceous -- even asymmetric -- feathers. Do you really want that? |
Don't ask him that....
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T. Michael Keesey
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David Marjanović
Joined: 24 Aug 2006
Posts: 137
Location: currently Paris
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| Posted: Sat 02 Sep, 2006 8:28 pm Post subject: |
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Why?  |
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dinoguy2
Joined: 22 Aug 2006
Posts: 41
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| Posted: Sun 03 Sep, 2006 12:56 am Post subject: |
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| David Marjanović wrote: |
Then why are you calling yourself "dinoguy"? Even if you mean that all parts of the pennaceous feather must be present, you still get a good chance of having Achillobator as a bird, because Microraptor has pennaceous -- even asymmetric -- feathers. Do you really want that? |
You just illustrated a tangiential philosophical/public relations reason to use apomorphy clades. You can discover that an animal has been mis-assigned. There was something nice about being able to make a new discovery and say, "hey, turns out Achillobator is actually a bird. We had it wrong before." It allows for a sort of paradigm shift in the way you think about an animal. I argued recently on Dinoforum that a problem with a lot of modern paleoart is the fact that artists tend to slap feahters onto animals that still retain the "look" of oldschool "reptilian" dinosaurs. My hunch is that this is due to the new forms of nomenclature being used. If we told people that Utahraptor is in fact a bird, that *clicks* more, and creates an instant impression of, in general, how these things were. Scientists are doing a poor job of conveying to people just how birdy feathered non-avian dinosaurs were, to the point where i've had people tear me apart for trying to include John Conway's Deinonychus drawing on wikipedia because "it looks like a puffin" (http://en.wikipedia.org/wiki/Talk:Deinonychus#Image). If these things which look so much like birds are just called birds, it would clear up a lot of misconceptions.
And yes, I know science isn't about public relations. But that doesn't mean it doesn't cause a few problems here and there.
So, what's wrong with Achillobator being a bird? It's just a big giant kiwi
| tmkeesey wrote: |
Don't ask him that.... |
Now he's learned his lesson  |
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David Marjanović
Joined: 24 Aug 2006
Posts: 137
Location: currently Paris
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| Posted: Sun 03 Sep, 2006 12:09 pm Post subject: |
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Oooookaaaay... but if that is your concept of "looks like a bird", why don't you put an oviraptorosaur into the definition? That would make sure Caudipteryx is inside -- and most probably Therizinosaurus, too.  |
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dinoguy2
Joined: 22 Aug 2006
Posts: 41
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| Posted: Sun 03 Sep, 2006 4:53 pm Post subject: |
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| David Marjanović wrote: | | Oooookaaaay... but if that is your concept of "looks like a bird", why don't you put an oviraptorosaur into the definition? That would make sure Caudipteryx is inside -- and most probably Therizinosaurus, too. |
That's why I don't like using species in the definition--the fossil record is too incomplete. Using some sort of feather apomorphy would pretty much cover any future discoveries. |
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tmkeesey
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Joined: 14 Aug 2006
Posts: 287
Location: Los Angeles, CA, USA
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| Posted: Sun 03 Sep, 2006 5:11 pm Post subject: |
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Well, you have to use a species (or specimen) somewhere in an apomorphy-based definition, because otherwise your definition could be polyphyletic. (Probably not the case for pennaceous feathers, but still....)
And secondly it's because the fossil record is incomplete that apomorphy-based definitions are generally not desirable. If we were to use your preferred definition of Aves (which is equivalent to Avipinna Gauthier and de Queiroz 2001), we could know a fossil animal's exact phylogenetic position and still not know whether it was avian or not. If it ...- ... were outside the node-based clade specified by all known possessors of pennaceous feathers, but ...
- ... shared more recent ancestry with that clade than with any animal known for certain to lack pennaceous feathers, and ...
- ... lacked any evidence as to its own integument ...
... then it would be in "avian limbo".
I think it's okay to erect definitions like this, but not, in most circumstances, for popular, well-known names. So let it be the definition of Avipinna but not of Aves.
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T. Michael Keesey
Director of Technology, Exopolis, Inc.
Last edited by tmkeesey on Mon 04 Sep, 2006 12:05 am; edited 1 time in total |
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David Marjanović
Joined: 24 Aug 2006
Posts: 137
Location: currently Paris
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| Posted: Sun 03 Sep, 2006 8:59 pm Post subject: |
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| I agree. |
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dinoguy2
Joined: 22 Aug 2006
Posts: 41
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| Posted: Tue 05 Sep, 2006 5:53 am Post subject: |
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| tmkeesey wrote: |
I think it's okay to erect definitions like this, but not, in most circumstances, for popular, well-known names. So let it be the definition of Avipinna but not of Aves. |
Guess we'll have to agree to disagree then, since this just brought us back around to one of my original points--that since originally and traditionally Aves was used for the apomorphy based clade, Aves should stay with it, and let the newer name be assigned to the newer clade whose contents are more concerete. In otherwords, I'd switch the definitions of Aves and Avipinna (though replace the later with Avialae).
In other words, yes Aves is popular and well known, but for most of its history it was popular and well-known for a "definition" to which it is not applied in PN. More precise to re-assign it maybe, but also more confusing, especially to non-specilists in this particular field. |
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tmkeesey
Site Admin
Joined: 14 Aug 2006
Posts: 287
Location: Los Angeles, CA, USA
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| Posted: Tue 05 Sep, 2006 6:25 am Post subject: |
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| dinoguy2 wrote: | | Guess we'll have to agree to disagree then, since this just brought us back around to one of my original points--that since originally and traditionally Aves was used for the apomorphy based clade |
I beg to differ. "Aves" has never been used for an apomorphy-based clade. Traditionally it was used for an "I know it when I see it" group, and under phylogenetic nomenclature it has been given two different node-based definitions (Gauthier, Chiappe). (There's also Marjanovic's branch-based definition, which has not yet been published.)
You say you want the clade definition to match the traditional usage, but using the Avipinna definition would expand it. Indeed, David Marjanovic's definition of Aves is the only one I've seen that really tries to capture the traditional usage, insofar as it can be captured by a rigorous definition. (Chiappe's comes close as well, but it potentially includes dromaeosaurids, troodontids, etc.)
The fact is, before PT, "Aves" just meant "birds". Nothing more or less precise than that. Originally, the category was quite clear, but, starting with Archaeopteryx, organisms were discovered that did not clearly belong or not belong. Only in recent decades have people really started to create a rigorous definition, and since the taxon has been historically so fuzzy, there is naturally a lot of disagreement about where to draw the line. This is, of course, a problem for all lineages with decent fossil records.
There is a direct parallel with the recent Pluto situation. "Planet" had never been rigorously defined. The decision came down to using a definition that excluded a traditional planet or one that potentially included many things traditionally not considered planets. The IAU opted for the former.
Now there is a chance to finally define "Aves". Should we opt for a definition that is difficult to apply, or one that is straightforward? Should we err on the side of including non-traditional content, or on the side of excluding traditional content? The IAU opted for the latter options when defining "planet". I think it's best to do so for "Aves" as well, and I think it's best to adopt a similar stance wherever this kind of problem crops up.
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T. Michael Keesey
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