[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Combined answer: smallest ANCIENT non-bird dinosaur - was what I was asking

Regarding the original topic of this thread, what about *Parvicursor*, now that the alvarezsaurids are (...probably...) not birds? (Hat tip to Raymond Tobin.)

----- Original Message -----
From: "Jeff Hecht" <jeff@jeffhecht.com>
Sent: Friday, May 02, 2008 2:39 PM

A general observation in reaction to this discussion -- having watched the public reaction to astronomers trying to redefine Pluto as a 'dwarf planet,' I would be wary of the public reaction to attempts to redefine birds in a way that leaves out Archaeopteryx. Astronomers had a fair justification for reclassifying Pluto, but they failed completely in justifying it to the public, who have long been taught Pluto was a planet, and concluded it was hair-splitting silliness.

(Actually, I don't quite understand why "dwarf planet" isn't considered a subcategory of "planet", the way "terrestrial planet" and "gas giant" are, rather than something completely separate. -- But there is no analogy here to biological nomenclature, because celestial bodies don't reproduce. They don't have a phylogenetic tree.)

To the public who pay attention to such things, Archaeopteryx is the first bird. They would accept a flyer earlier than Archaeopteryx as a bird, but they would not accept trying to exclude Archaeopteryx on some arcane anatomical or cladistic grounds.

I think many would prefer it if the only alternative were accepting *Utahraptor* as a bird, though. What if Archie is a troodontid and deinonychosaur...?

Reclassifying something so fundamental -- and on some level so obvious -- could make evolution seem a less-certain science than it is.

That said, everything can be quote-mined -- and almost everything already has been -- to support this fallacious conclusion. http://en.wikipedia.org/wiki/Quote-mining

----- Original Message -----
From: "T. Michael Keesey" <keesey@gmail.com>
Sent: Friday, May 02, 2008 11:11 PM

If these names are forced to mean something, then I have to agree with
Gauthier that in general the crown group is best, as it limits
unwarranted inferences.

This is true in one direction (it discourages unwarranted extrapolation of crown-group autapomorphies to larger clades), but not in the other. Is hair a mammal autapomorphy? Not if we use the crown-group definition(*): the docodonts (*Castorocauda*) had hair, too.

Of course, if we're talking about mammals, most people simply forget the monotremes most of the time. I already mentioned once that I've read in a popular book: "*Morganucodon* was a mammal because it bore live young." The *Beelzebufo* it did. Not only don't we have any direct evidence on the reproduction of this stem-mammal, but phylogenetic bracketing suggests very strongly that it laid eggs. ARRRRGH!!!

(*) The definition as the *Sinoconodon* node seems to be in at least as common use. It's by Luo, Cifelli & Kielan-Jaworowska 2004, and conforms to the most common pre-PN concept of Mammalia, except for the exclusion of the isolated braincase called *Adelobasileus*.

For example, let _Cetacea_ refer to the crown group,

Of course, this crown group is already called Autoceta Haeckel 1866 and has 922 ghits (down from 978 less than a week ago... weird...).

_Pan-Cetacea_ or pan-Cetacea to the total group,
"stem-cetaceans" to the stem group, and perhaps coin new names for
apomorphy-based clades ("Cetorrhini", "Cetopoda", "Cetoplota",
"Cetorachiopinnae", "Ceturopinnae", etc.).

Yes -- except if you're more interested in teeth and middle ears than in gross shape. Then it becomes interesting.

And if you had a foot fetish you'd call _Coelophysis_ a bird....

Sure, but teeth are much more common in the fossil record, and the petrosal ( = fusion of pro- and opisthotic) is said to be the hardest bone in the mammalian skeleton -- isolated petrosals are indeed fairly common in the fossil record.

----- Original Message -----
From: "T. Michael Keesey" <keesey@gmail.com>
Sent: Saturday, May 03, 2008 2:32 AM

(Random fact: The names of the species of *Sphenacodon* are among the
coolest ever. First there's an ordinary *S. ferox* -- and then there's *S.
ferocior*, the comparative, the "even fiercer one".)

Neat. Can _S. ferocimus_ (sp?) be far behind?

Would be ferocissimus... but I really don't recommend the use of superlatives in the names of fossils! Think about how many sauropods could have been named "maximus" or "gigantissimus" over the last 100 or even just the last 20 years...

----- Original Message ----- From: "Tim Williams" <twilliams_alpha@hotmail.com>
Sent: Sunday, May 04, 2008 6:30 AM

http://en.wikipedia.org/wiki/Image:Pakicetus.gif

Now you're cheating, Mike! Get this thing off dry land, and put it in the water. Then we'll see how "whale-like" it really is! :-)

http://critters.pixel-shack.com/WebImages/crittersgallery/Pakicetus.jpg

To be fair, this picture seems to have been made when only the skull was known. Basically, the postcranium is all wrong.

----- Original Message ----- From: "T. Michael Keesey" <keesey@gmail.com>
Sent: Monday, May 05, 2008 3:40 AM

Thirdly, we already have a name for the crown-group: Neornithes. Further, Neornithes has been used for the avian crown-group for a very, very long time.
[Gauthier and de Queiroz (2001) propose a whole new definition for Neornithes, and make it *more* inclusive than Aves!] 

The definition that they consider (but do not explicitly propose!) is
based on the original usage, which was as an explicit substitute for
_Ornithurae_ that included _Hesperornis_ and _Ichthyornis_ . Its usage
for the crown group is a somewhat recent innovation. (How recent, I'm
not exactly sure, although as late as 1983 Martin included
ichthyornithiformes therein.)

I disagree. All usages of Neornithes that I've seen that included *Hesperornis* and/or *Ichthyornis* seem to have been made in the context of the hypothesis that these animals really were crown-birds. FÃrbringer (1888 -- yes, I've seen that book) explicitly said so (except of course in different terms), and for much of the 20th century it was thought that, while the hesperorniths were outside the crown because of their teeth and other features, the toothed jaws associated with *Ichthyornis* actually belonged to a juvenile mosasaur and that *I.* was a crown-bird; perhaps I can check Martin 1983 tomorrow, but this paper is in any case in the right timeframe for this hypothesis. The suggestion by Gauthier & de Queiroz (2001) is the only case I'm aware of where Neornithes was not meant to be a crown-group.

Personally, I like the idea David Marjanovic proposed, that a clade
resembling the traditional one used in paleontology (which his
definition approximates much better than the node-based definition
does, IMO) could be named "Ornithes" (currently, and somewhat
bizarrely, an unused name). Then there'd be no problem whatsoever
using "bird" to refer to that clade.

For the sake of completeness, this is my Plan B. My preference would be Aves and Neornithes rather than Ornithes and Aves. -- The reason why Ornithes does not currently exist is that Aves exists and means the exact same thing, only in Latin rather than Greek; Greek nouns are more prefix-friendly than Latin ones, which is why Neornithes, Hesperornithes, Archaeornithes and Enantiornithes were coined long before Neoaves, Metaves and Coronaves were.

----- Original Message -----
From: "Dann Pigdon" <dannj@alphalink.com.au>
Sent: Wednesday, May 07, 2008 3:06 AM

The real question is whether Archaeopteryx 'deserves' to be within Aves (if 'Aves' is still even in use). This is simply a question of how scientists choose to define such a classification, since there is really no such thing as a 'natural' grouping. All classification systems are ultimately arbitrary.

There is of course such a thing as a natural grouping -- clades really exist --, but of course how we name them and which ones we name is arbitrary, so your point stands.