2.21.2010

Tawa is a Jerk

Tawa. Four little letters that are simultaneously breathtaking and infuriating. What the heck is a Tawa you ask?

Yes, I know you didn't ask. If you did, you wouldn't have typed "Tawa" into the search bar. I love it for because no matter what other bullshit it caused, it will always be remembered by me for setting the "Coelophysid-Averostran" monophyly thing in stone, and that's nice, but it wasn't strictly necesary. I don't anyone really still though that Coelophysids were Ceratosaurs or anything stupid like that anymore.

Whats disturbing about it is the reactions real, honest-to-goodness, professional scientists are having to it.

So, Tawa is basal to both Coelophysids and Averostrans, forming a sort of sister group while still being recognizably Theropodan. The trick is it also holds on to some Herrerasaurid traits, traits that a) you'll have to go to tetrapod zoology or something similar to read about and b) decisively indicate that Herrerasaurs are close to the ancestry of Theropods, and must have occured after the Theropod-Sauropodomorph split, which then makes "Eusaurischia" paraphyletic and therefore not real except in magical Linnaen fantasy land.

I'm jumping straight to the point here because I already wrote something like this on my faceplace and because I assume if you searched for this you're already familiar with what I'm talking about. Tawa has been cited as suring up Herrerasaurids AS THEROPODS! This makes absolutely no sense to me, and I'm not going to pretend what the hell is wrong with some people just for the sake of argument.

First, the analogy: Remember when Pluto stopped being a planet? Didn't we all have a pretty curious reaction? Sure, anybody with a brain and an interest in the way the world actually works must maintain an objective viewpoint with all this science stuff, but saying Pluto was not a planet was a bit of a jolt to a lot of people. Funny thing is, it actually is still a planet.

You see, they redefined Pluto as part of a new category of celestial body called "dwarf planet," and said that they say is not a planet. For those of you who figured out the answer already, go ahead and skip this paragraph while the others catch up. The new category is a great idea in itself, because at the time countless numbers of little pluto-sized planets were being discoverd all over the solar system, so it seemed that Pluto is not an odd man out, but just a member of a different type of family, which makes perfect sense. "Dwarf Planet" is a perfect name for object like Pluto, as well as Sedna and Ceres, because that's what they are... small rocky planets that formed under similar conditions. Nothing wrong here, all the work is sound... so how do we get from Pluto being a new class of celestial body to it being legal to own dwarf people as slaves, being that they are no longer considered people? Who's job was it to proof read this stuff? Still don't get it? Here's the answer: a dwarf PLANET is still a PLANET, because the word DWARF does not negate the following word. If Pluto was a NON planet or ANTI planet, it would not be a planet. But Pluto is a DWARF... PLANET... a small planet that is now part of a special class, just a GAS GIANT, which doesn't eve have PLANET in the name. And nobody is saying Saturn isn't a planet are they?

So that's the situation with Tawa. Maybe some of you haven't figured out why calling Herrerasaurs "theropods" is a pretty stupid idea yet. That's okay, I'm going to illustrate it for you.

This is a cladogram of the relationships between Saurischians before we found Tawa. It features the now known to be paraphyletic "Eusaurichia." Notice the position of THEROPODA and Herrerasaurids:

SAURISCHIA
|--Herrerasaurids
`--Eusaurischia (I bet Eoraptor goes here)
   |--+--?Guaibasaurids
   |  `--Sauropodomorphs
   `--THEROPODA
      |--Coelophysids
      `--Averostrans
         |--Ceratosaurs
         `--Tetanurines

So, I'm not certain on where Guaibasaurids were supposed to fit, since I heard they were closer to both Theropods and Sauropodomorphs. Just for shits and craps, I'm putting them up with Panphagia. Pay close attention to the organization of Theropoda, so you can see just how much turmoil Tawa has thrown it into... truly it must be heinous. Here is the family tree after Tawa:

SAURISCHIA
|--+--?Guaibasaurids
|  `--Sauropodomorphs
`--THEROPODA
   |--Herrerasaurids
   `--+--Tawa hallae
      `--Neotheropoda
         |--Coelophysids
         `--Averostrans
            |--Ceratosaurs
            `--Tetanurines

Do you see it? Do you see the unruly state of affairs that the Theropods have been reduced to? 'Cause I sure as hell don't. So right away there's the obvious fact that nothing actually changed within Theropoda. It's now called "Neotheropoda" for no good reason. Go back and look at the other cladogram, go ahead and scroll back up, I'll wait. You see the yellow text? It's the same isn't it? Yeah, it is.

Now i'm going to introduce my new cladogram, based on a bunch of heresay and subjective nonsense that has no real basis in reality. Surely, this table is is amatuerish at best:

SAURISCHIA
|--+--?Guaibasaurids
|  `--Sauropodomorphs
`--+--Herrerasaurids
   `--THEROPODA
      |--Tawa hallae
      `--Neotheropoda
         |--Coelophysids
         `--Averostrans
            |--Ceratosaurs
            `--Tetanurines

The joke here is that, of course, this isn't my amatuerish cladogram, it's the same one as above, but proof-read. I moved the word THEROPODA to it's original position, included Tawa because I can see the kink in the jaw from where I'm sitting, and just to be nice, I even kept the "Neotheropoda" part.

The moral of that: Tawa didn't change anything within the cladistic structure of Theropoda, it only reaffirms the monophyly of the whole "Coelophysid-Averostran" set-up. It DOES INDEED move Herrerasaurs into a position close to Theropods, but it does not MAKE Herrerasaurids Theropods.

Let me repeat that: Tawa is a Theropod that retains traits from the last common ancestor of Herrerasaurids and Theropods, but DOES NOT place Herrerasaurids within the pre-established and recently strengthened monophyletic "Coelophysid-Averostran" Theropoda.

There is no need to say Herrerasaurids are Theropods. Turns out a lot of our old ideas about the placement of Herrerasaurids was indeed not the case, but our understanding of what is and isn't a Theropod actually looks clearer now. So there's too more things I need to address: 1) Why can't we move Theropoda to cover Herrerasaurids anyways, and 2) What makes a Theropod a Theropod anywhichways?

1. Herrerasaurids as Theropods is far from a new idea. Idiots have always argued for their inclusion. Does that sound harsh? Take a look at the facts: the ancestor of all dinosaurs was obviously a carnivore, probably an omnivore but let's not bet on it. Therefore, all basal saurischians closer to Coelophysis than Panphagia should have been carnivorous as well. So, a small meat eating dinosaur from the late Triassic could be almost anything. So meat eater does not equal Theropod.
Now, like the Pluto thing, Theropods are a personal issue for me, so I have a hard time being objective about these things. That said, the more radical the idea, the easier it is to be openly biased. I agree that outwordly, Herrerasaurus does look like a Theropod, but that isn't enough for me to except him as a relative to something like Tyrannosaurus or Aquila. Theropods are special for a reason, a whole slew of physiological reasons that some primitive saurischian just can't compete with.
So, I can back up my personal feelings in this case because Theropods really are very different than other dinosaurs, I could say better too, but then that's crossing the line.

2. Quick, name one thing only Theropods have and all Theropods have. It's okay if only very specialized forms that no one debates are Theropods don't fit, I'm looking for something clearly identifiable in Coelophysis and 90% of it's descendents, but NOT in any other animal.
Give up?
Well, the answer I was looking for was a wishbone or furcula. I've never heard of any other animal having a true wishbone. I have heard that Massopondylus (and I guess all Massospondylids?) have something LIKE a furcula gained from convergent evolution, but that's about it.
And that was the last nail in the coffin for me. According to Tom Holtz, who I'm going to totally trust on this because I can't find any other source on the matter, no known Herrerasaurids have been shown to possess a furcula. So, they can't be Theropods. It's all really very simple.

I am pretty stubborn about this, sure, but I've got a damn good reason. The case for Herrerasaurids being Theropods is valid ONLY when you find a Herrerasaurid with a wishbone. I except the conclusion that they are closely related, so don't bite me, Tawa.

I think I've already beaten this to death, but the real moral here is that scientists need to proof-read and stop missing such obvious crap. It's irritating when you hold someone's logical reasoning ability to such high esteem only to find out that they didn't realize calling something a dwarf planet does not mean it isn't a planet.

Also would someone please write a god damn Averostra article on wikipedia? It's 2010 now, this shit is getting ridiculous.

9 comments:

  1. Since Theropoda is a stem-based clade rather than apomorphy based, herrerasaurids are theropods as long as they turn out to be closer to Passer domesticus than Saltasaurus loricatus. If herrerasaurids turn out not to have a furcula, all that means is that the furcula is diagnostic of Neotheropoda rather than Theropoda. It doesn't dictate whether or not a certain dinosaur is a theropod.

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  2. Tell that to Tom Holtz. I believe theropod was originally defined by the shape of the foot... um, you know, like it says in the name. Not all clades started in the age of enlightenment, some of them really are holdovers from linaean days that have just been updated with the times.

    Also, I hate to sound like a broken record here, but my point is that, as is quite remarkable in the time of Tianyulong, nothing about theropods changed. Turns out the kink is basal, so I guess avero's had it early on too, but the theropods themselves are unchanged.

    It's the same damn thing that happened to pluto, the words didn't actually change, your attitude did.

    And as much as an opinionated asshole I am, that's just not good science.

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  3. Holtz puts herrerasaurs within Theropoda and has the furcula as a neotheropod thing on his site now... http://www.geol.umd.edu/~tholtz/G104/lectures/104therop.html

    And even though Theropoda was coined way back then, these names have now been redefined phylogenetically, so that's really the way to go. Celestial things are different, they aren't constrained by phylogenetic definitions.

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  4. The he's a fucking traitor. Also, when exactly was Theropoda redefined? As far as I know, the only time that's happened to dinosaurs was when Aves included archaeopteryx + crown group, but that is a sticky mess now, and the only safe definition of aves is crown group period. But all of those words get mixed around, and they all mean the same thing down there. Sort of. Point is, if they stick with the "new" one, paraves = birds, which is just silly.

    Pluto is obviously not the same type of celestial body as a rocky/terrestrial planet like us or Mars, but the statement "Pluto is no longer a PLANET, it is a dwarf PLANET" makes no sense logically, which is something scientists are supposed to be good at (but never really are). Since then, asteroids have been added to a larger group of objects called "minor planets," so now most objects in the solar system are some type of planet.

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  5. Sereno defined Theropoda in 2005. And Neotheropoda is hardly a new thing, it was around in 1986 and also defined in 2005. (Neotheropoda is the least inclusive group containing Passer domesticus and Coelophysis bauri, so until Tawa was discovered and herrerasaurs and Eoraptor came out closer to Passer domesticus than to Saltasaurus loricatus Neotheropoda wasn't used because it was good as identical as Theropoda at the time.)

    Planets aren't defined phylogenetically, so moot point. The authors of the Tawa paper found herrerasaurs closer to Passer domesticus than to Saltasaurus loricatus, ergo theropods, and that's all there is to it. Nothing else matters. You can criticize how they came to that conclusion (the rigor of the analysis and such), but not the conclusion itself.

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  6. Quick notes: first phylogenetic definition of Theropoda was in 1986, and that of Neotheropoda was in 1998. Current working definitions both in 2005.

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  7. By the way, I haven't heard of the Paraves = birds thing. To my understanding the most common use for birds tends to be Archaeopteryx + Passer.

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  8. That's what I said. If Aves = Archaeopteryx plus CG birds then Aves = Paraves. Archaeopteryx was found in a different time, they didn't know how primitive it was in the 1860's, they just saw feathers and went ape shit.

    I'm not seeing it here, but I remember leaving a response to your idea that the first definition doesn't "count" and so somehow a second one takes precedence. It's silly, is all.

    Also you seem to have completely missed the point about using the dwarf planet issue to compare how otherwise intelligent people are capable of really embarrasing mistakes that they refuse to back down from, and thus make themselves look like jackasses. What they did with Tawa is one of those things, I didn't mean to confuse you or anything, it's just an analogy.

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  9. I wouldn't be surprised if Archaeopteryx was less close to crown group birds than were deinonychosaurs, but most current analyses still put it closer to the crown group. So Aves isn't Paraves. Yet.

    The earliest phylogenetic definition of Theropoda was "Birds and all saurischians that are closer to birds than they are to sauropodomorphs". Under that herrerasaurids are still theropods if you accept the results the Tawa paper. If you want to use the real "first" definition then you should be using it as a Linnean rank and not a clade at all.

    I do not see how this is a "mistake". Even if Theropoda hadn't been redefined in 2005 or whatever herrerasaurids would still be theropods under every single phylogenetic definition Theropoda has ever had (and really, all these redefinitions do is change the wording, they don't actually change the meaning: http://www.taxonsearch.org/dev/taxon_edit.php?Action=View&tax_id=310) according to the Tawa authors.

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