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Albertonykus β Vertebrata Phylogeny
#birds #amphibians #dinosaurs #fish #mammals #reptiles #vertebrates #phylogeny #synapsids
Published: 2017-05-15 01:01:35 +0000 UTC; Views: 2512; Favourites: 53; Downloads: 78
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I said I wouldn't be updating the Big Vertebrate Tree , but so long as Drs. Holtz and Merck continue making their course materials available publicly, there's nothing stopping me from updating just its general topology. Taxa in bold have extant representatives. I have graduated from UMD, and do not have inside info on why specific topologies may have been favored over alternative hypotheses.Edit: No (intentional) changes to the topology here, but I discovered the program TreeGraph for manipulating phylogenetic trees and decided to redo this tree using it. The aesthetics and readability have improved a good deal, I think.
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Comments: 62
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Is traditional Gasterosteiformes (including syngnathiforms) monophyletic? I see you use Syngnathiformes here, but I don't know if that's because Gasterosteiformes is polyphyletic or Syngnathiformes is preferred over Gasterosteiformes for some reason.
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I can't pretend to know anything about actinopterygian taxonomy. I used Syngnathiformes because Merck used Syngnathiformes, and he used it because Betancur-R et al. (2013) used it. However, Betancur-R et al. do state that they found traditional Gasterosteiformes to be polyphyletic and that they instead consider gasterosteids to be members of Perciformes, so that's probably the answer to your question.
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Where are lophiiforms? Aren't they close to tetraodontiforms?
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This doesn't include all the teleost groups.
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It must have taken a ton of research to complete this. Congrats. Though, you forgot Hiakouichthys and nectridean lepospondyls. But I have an even bigger question.
Why do fish only make up 20% of the tree when the majority of vertebrates are fish?
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This is based largely on a course I took as an undergrad. Because it wasn't a paleoichthyology course, more emphasis was naturally placed on groups that had spawned a greater body of literature (mammals) and the instructors' own research interests (reptiles). "Nectrideans" were excluded because they might not be a monophyletic group (see e.g.: Ruta and Coates, 2007 ), and Haikouichthys is probably closely related to (if not the same as) Myllokunmingia.
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I know nectrideans may not be monophyletic, but why did you exclude a big portion of the lepospondyls is what I'm asking.
I feel like people have a skewed view of vertebrates, that fish are just one group. In reality, the majority of vertebrates past and present are fish. The fish is the default vertebrate. Tetrapods are just weirdly derived terrestrial fish. But anyway.
I can understand the simplification of fish, but I still kinda wish you went further into percifomres. That's just me.
I have a proposal. Instead of Myllokunmingia, how aboutΒ Myllokunmingiidae which includes both Haikouichthys and Myllokunmingia (as well as Zhongjianichthys)
And why are pederpes and ichthyostega excluded from tetrapoda when they are quite clearly tetrapods?
And one last thing. It's actually quite possible that conodonts are not even vertebrates.
www.researchgate.net/publicatiβ¦
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Again, this is simply a summary of the course materials provided in a class that I took. As such, it was shaped by constraints imposed by the nature of the course and decisions made by my instructors. We covered the existence of "nectrideans" and Haikouichthys, but we didn't go into enough detail about their systematic position to include them in the "summary diagrams" that my instructors compiled. Ichthyostega and Pederpes are not "clearly tetrapods" if you use the crown-group definition of Tetrapoda, which is what we did. (If anything, they are clearly not crown-tetrapods.) We did mention that the position of conodonts is uncertain, but considered that the weight of the evidence was sufficient to tentatively favor them being vertebrates. If I had made this diagram entirely from scratch instead of using the course as a framework, it would probably look slightly different (though I doubt it would be different enough to motivate me into doing it).
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I wonder. Why use the crown based definition for tetrapoda over a node based one? I know that your course probably used the crown definition, but I wonder if there was a reason for it.
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Crown-group definitions are inherently node-based (in this case, the last common ancestor of lissamphibians, mammals, and reptiles and all of its descendants). More inclusive definitions of Tetrapoda are usually stem-based (anything closer to crown-tetrapods than to lungfish) or apomorphy-based (the first ancestor of crown-group tetrapods to have four limbs with digits and all of its descendants).
My instructors aren't fans of apomorphy-based definitions (and neither am I, frankly), mainly because features that we think are distinctive in hindsight have often undergone intermediate stages during their evolution that make it difficult to determine at what point they can be considered to be first present in a clade. As for using the crown-group definition over the stem-based one, the general trend (at least in vertebrate paleontology) is to apply "classic" names to the crown group (as has been done for Archosauria, Lepidosauria, Mammalia, etc.). Additionally, the earliest total-group tetrapods (like rhizodonts) weren't particularly similar to crown-tetrapods, which some might find confounding. In that case, might as well apply the name to the group that we can be certain had all the characteristics we associate with the name, at least ancestrally (i.e.: the crown group). But it's a matter of personal preference in the end. I don't think it's a big deal as long as it's clear which definition is being used.
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I get that apomorphy based definitions can be vague at times, but crown definitions aren't perfect themselves, as determining weather an animal belongs to clade or not based on weather it's alive is kinda weird. If pederpes was still alive, we would consider it a tetrapod.
Plus, apomorphy based clades are kind of necessary. Important traits may not have originated with the total group or crown group, but somewhere in the stem group, as is the case with tetrapods. Limbs with digits first appeared in elginerpeton, and appeared in later 'tetrapods' that aren't in the crown group. Some stem members such as pederpes have quite robust walking limbs. So, an apomorphy based clade that includes some but not all the stem group is necessary. This clade already exists, it's called stegocephalia. But, I feel like that stegocephalia should just be tetrapoda and the crown group can be eutetrapoda.
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Sure. Whatever naming scheme we use, there will always be some arbitrary metric involved in deciding how we apply it. That's why I don't consider it a big deal that different people use the term Tetrapoda differently.
However, I don't think apomorphy-based clades are necessary. We can discuss the acquisition of key features without defining clades based on apomorphies. For instance, we could name a node-based clade based on the last common ancestor of Pederpes and crown-tetrapods and say that increased terrestrial habits likely arose in that clade, instead of defining the clade based on features supposedly associated with terrestriality (and unnecessarily delimiting what was almost certainly a gradual process).
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I guess it all just boils down to preference of application, huh?
On a side note, how long would it take to make a tree like this but for arthropods?
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Indeed. As for arthropod phylogeny, it would depend on how detailed you want it to be. Doing the relationships between the different "classes" might not be too bad, but one could also go much, much deeper... Potentially it could be much bigger than this tree (which took a few hours). Funnily enough, I'm working on arthropod phylogenetics right now, so maybe I'll make a diagram like this for arthropods at some point.
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Ooh, I'm hyped.
And by arthropod phylogeny, I mean deep. Like going in depth for each insect order, each arachnid order, all the paleozoic miscellaneous groups, and so on.
But regardless, I'll be waiting.
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I don't know that I'll go quite that deep. Even so, it's early days and nothing's set in stone. I'll let you know when/if I finish it.
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Okay then. It was wonderful talking to you
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How are you doing?
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Good, thanks. What's up?
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Good, good. How's everything going?
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Started embarking on a PhD, for one thing. (On vertebrates, not arthropods, sorry.) Busy but exciting times ahead.
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What's the PhD about what, specifically?
Anyway, have ya' made any progress on tree of arthropods? I'm not trying to rush you, take as long as you need. I am just curious.
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I'm studying fossil birds and various aspects of avian evolution. You may need to wait a while yet for the arthropod tree, I'm afraid. It's one of many items on my to-do list, but I can't guarantee when I'll do it. You will hear about it if I finish it.
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You know what's funny? If all vertebrates died, they would technically be stem tunicates. Or if all animals and related organisms died, they would all be stem fungi
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Don't worry. I will be as patient as needed.
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What? Shouldn't the germanodactylids be closely realated to the dsungaripteroids? If not can I get the paper about it?
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The pterosaur section looks like it's based on the Andres topology .
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Absolutely amazing. Just a heads-up, but Barbourofelidae is in bold when it shouldn't be...unless Drs. Holtz and Merck taught you something the rest of us don't know lol.
Also no Hyaenidae coming out of Feliformia.
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Good catch, thanks. It's been fixed. Hyenas are part of Viverroidea.
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Are they now? Huh. Guess I have to refresh my mammal phylogeny lol. And no worries, glad to be of help.
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Typo. Fixed now.
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Followup comment because dA won't let me edit:
Does Brevirostres still exist?
Did you forget turtles?
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Brevirostres is not favored by molecular and combined phylogenies. I suspect it's on its way out...
I didn't forget turtles. (Hint: turtles are covered last in this course.)
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The old Cimolesta is back?
Where do mesaxonian dinoceratans come from?
How secure is the new position for desmostylians?
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I'm not positive, but I think Cimolesta is mostly based on one of the alternative topologies found by Halliday et al. (2017) (check the supp). Naturally, it goes without saying that almost everything about the phylogeny of Paleocene mammals is in a state of flux.
The position of dinoceratans is based on an unpublished study by Benjamin Burger. (There's a video of him discussing this research here .)
We need more studies to make a call on the position of desmostylians in my opinion, but Gheerbrant et al. (2016) found them to be highly unstable either way (though they do argue that recovering them as afrotheres is the result of long-branch attraction), so I wouldn't make myself too comfortable.
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Not too mad, or else I would have included the synapomorphy lists and silhouettes, too...
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I assume your not a fan of the new dinosaur family tree?
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This diagram is based on a course taught by Thomas Holtz and John Merck, so if Holtz (who teaches the dinosaur section) didn't follow the Ornithoscelida hypothesis for the course, I didn't use it here. (That being said, I have it on good authority that he did discuss the possibility in class.)
My personal view on the Ornithoscelida hypothesis is that there's no obvious reason to automatically reject it. That's not to say that we should rewrite all the textbooks posthaste, but that we need other researchers to independently test it to find out just how robust it is (which is very likely going on as we speak).
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Do you know how these are formulated?
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Are you asking how I made this diagram, or how researchers figure out these phylogenetic relationships?
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