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GEOL 431 (The Big Vertebrate Tree)

By Albertonykus
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A phylogeny of vertebrates I made as a study guide for my peers in Vertebrate Paleobiology. Information compiled by Drs. Thomas Holtz and John Merck, but any errors are probably mine.

Taxa in bold have extant representatives. Taxa for which monophyly is uncertain are followed by a question mark. Taxa whose phylogenetic position is less certain than presented here are preceded by a big orange question mark (this excludes those whose uncertainty is already indicated by a polytomy). In the lower right is a short list of taxa so problematic that we did not deign to place them in even a tentative position on the phylogeny (though we may have ideas about what major groups they belong to). This should not be by any means treated as an exhaustive list of controversies in vertebrate phylogenetics, as I have only indicated those we brought up in class.

All silhouettes are from PhyloPic, with the exception of the parvicursorine, which was generously made for me by :iconspikeheila: when I lamented that I could not find any alvarezsaurid silhouettes on PhyloPic that were satisfactorily fluffy.

Due to the time and effort involved in creating an image of this size and nature, I am unlikely to update this on a regular basis. As such, this should be considered a snapshot of the state of the art and will inevitably become increasingly outdated as time goes on. However, a more up to date version including only the branching topology (but not the synapomorphy lists or silhouettes) is available here.
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PRM03's avatar

So Proterosuchus was not a thecodont? Didn't Prolacerta have thecodontian dentition like the Erythrosuchidae+Eucrocopoda clade?

Albertonykus's avatar

Thecodonty here is used in a stricter sense than simply having teeth set in sockets. Prolacerta, Proterosuchus, and many other non-eucrocopod crocopods exhibited ankylothecodonty, in which the teeth were not only set in sockets but also fused to the jaw, whereas plain thecodonty (as exhibited by Erythrosuchidae + Eucrocopoda) in this case refers to having teeth that are set in sockets but lack fusion with the jaw.

PRM03's avatar

Oh, makes sense. That distinction is actually useful.

SpongeBobFossilPants's avatar
Are xenungulates still afrotheres?
Albertonykus's avatar
No clarity on their phylogenetic position yet to my knowledge. I have some recollection of a recent conference abstract suggesting they are stem-perissodactyls, but don't remember where I found it.
SpongeBobFossilPants's avatar
Aren't paucituberculates sister to australidelphians?

Where would sparassodonts go?
Albertonykus's avatar
Traditional Ameridelphia is no longer considered to be monophyletic (see e.g.: Nilsson et al., 2010). The position of sparassodonts within Metatheria is uncertain.
SpongeBobFossilPants's avatar
I never said ameridelphians were monophyletic. I said paucituberculates were sister to australidelphians, leaving didelphimorphs outside.
Albertonykus's avatar
Sorry, I misread. The relationships between paucituberculates, didelphimorphs, and australidelphians are unclear.
SpongeBobFossilPants's avatar
In old topologies where caseids & varanopids were closer to each other than to ophiacodontids or therapsids, was Caseasauria ever used to include varanopids? I need to know for an April Fools joke I'm planning.
Albertonykus's avatar
Not to my knowledge.
SpongeBobFossilPants's avatar
What specific positions have been proposed for erpetosuchids?
Albertonykus's avatar
SpongeBobFossilPants's avatar
Do thalattosaurs not have a euryapsid skull?
Albertonykus's avatar
Ancestrally they did, but the supratemporal fenestrae were greatly reduced, and in many cases were lost. Here we used Euryapsida for ichthyosaurs + sauropterygians, regardless of anatomical condition.
SpongeBobFossilPants's avatar
Is the old Enaliosauria available for thalattosaurs + euryapsids?
Albertonykus's avatar
It's traditionally used equivalent to our Euryapsida, but if someone wanted to define it that way, perhaps.
SpongeBobFossilPants's avatar
Shouldn't ursoids & musteloids switch places?
Albertonykus's avatar
We were probably following the older, morphology-based topology for that one.
SpongeBobFossilPants's avatar
Since when are anthracotheriids ruminantimorphs?
Albertonykus's avatar
Since whichever study Holtz followed while preparing for this class. =P I'm aware they appear to be cetancodonts now.
SpongeBobFossilPants's avatar
I'm not particularly familiar with mammals (and I'm guessing you aren't either), but how would you rank these traditional ideas in order of likelihood?

1. Insectivora.
2. Bats sister to colugos within Archonta.
3. Pangolins sister to xenarthrans, with this clade close to Euarchontoglires.
4. Afrotheres close to laurasiatheres.
5. Fissipeda.
6. Procyonid pandas.
7. Suinan hippopotami.
8. Primate treeshrews.
9. Artiodactyls closest to carnivorans & perissodactyls closest to afrotheres.
10. Monophyly of noncetacean artiodactyls.
Albertonykus's avatar
Keeping in mind my modest knowledge of mammals, I don't consider any of these ideas to have a significant chance of coming back. Maybe traditional Insectivora and Archonta (but not including a bat + colugo clade) because of the number of morphological characters supporting them, though I wouldn't bet on it.
SpongeBobFossilPants's avatar
What do you think of Vislobokova's attempt to discredit cetancodont synapomorphies?

I also remember that orangutans, gorillas & chimps were once thought to form a clade exclusive of man. Is that dead in the water as well?
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