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The Cartoon Guide to Vertebrate Evolution
By Albertonykus   |   Watch
418 209 34K (1 Today)
Published: August 6, 2015
© 2015 - 2019 Albertonykus
In which I discover the pain of drawing non-avemetarsalian archosauriforms (so many osteoderms!) and ungulates.

I like to think that the Big Vertebrate Tree is a useful resource, but it's not very user-friendly. As such, I have produced a simplified (yes, this is simplified) and more vibrant vertebrate cladogram.

Animals that have been colored in are extant species. Age ranges represent known fossil record and do not include ghost lineages. The animals placed along the branches (instead of at the tips) are all based on real taxa that approximate the likely ancestral morphology of certain groups, but I have left them unlabeled to prevent propagation of the misconception that we can identify whether said taxa are the actual ancestors of those groups. Absolutely nothing is to scale.

My apologies if I butchered the anatomy of or left out any of your favorite lineages. There were an immense number of groups and characteristics I included in my original outline that I had to cut out for considerations of space and time. Those who desire a more in-depth depiction at vertebrate phylogeny should consult the Big Tree and the technical literature.

I am more inclined to update this image than the Big Tree. However, it is still a massive project by my standards, so major revisions (if necessary) will likely be irregular. Suggestions and corrections are welcome.

Adventure Time-style Darren Naish was designed by :iconclassicalguy:. Special thanks go to :icondracontes: for helping me visualize ear evolution in therapsids.
Image size
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Comments (203)
TheDarkMaster2's avatar
TheDarkMaster2|Hobbyist General Artist
Shame that the choristoides went extinct
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Phoenix-the-horse's avatar
Phoenix-the-horse|Hobbyist Traditional Artist
holy
this is great
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GayCoonie's avatar
Where do you put the likely devolopment of fur, and what do you think the upper and lower bound of that it? Crown mammalia obvoiusly has fur, and basal synapsids didn't, so how far would you narrow that down beyond that? It seems extemely likely that all or most cynodonts had fur, and I've seen reconstructions with animals as primitive as tetraceratops with it. 

Also, where do you put the devolopment of pycnofibres / proto-feathers? Do you think they're the same thing, and do how basal do you think they are? I know some people think they might be basal to all archosaurs even, so I'm wondering your position.

Personally, I don't think it's a stretch to think that insulating integument evolved in those lineages about the same time as endothermy, which seems to be pretty early for archosaurs, and somewhat of an open question for synapsids.
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Albertonykus's avatar
The unsatisfying but honest answer is that we currently don't know when fur evolved in synapsids. Based on the limited evidence that we have, I'd say that fur was probably ancestral to at least prozostrodontian cynodonts. There are undescribed dicynodont specimens that suggest they lacked hair, in which case hair most likely evolved at some point within theriodonts (gorgonopsians + mammals).

As for archosaur filaments, I personally suspect that homology between pycnofibres and feathers is likely, but I wouldn't consider it a closed case. What we need is a Triassic fossil site that preserves the integument of early ornithodirans to make more confident inferences. Contrary to rampant rumors in the amateur paleo community, I've yet to see any evidence that feathers were ancestral to all archosaurs. This notion appears to be a misinterpretation of developmental studies on modern crocodylian scales, which have found that crocodylians share some of the genetic toolkit that birds also use to make feathers. However, all this shows is that birds and crocodylians use some of the same "machinery" to make their integument, not that crocodylians ancestrally had feathers. Even we have many of the genes that birds recruited for feather development, after all.
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GayCoonie's avatar
Do we have any reason to think that any evidence of fur would even be preserved under such conditions? There are many conditions I can think of where the fur of a dead animal might disperse before the skin decomposes. Also, would fur even nessacarily show up in that sort of impression. Couldn't it be matted to the body at the time of preservation? The detail certainly isn't fine enough that it'd show up in that case. I think we'd need a lot more evidence to say definitively one way or another.

This paper suggests that basal archosaurs (and most other exitinct archosaurs), and even non-archosaur archosauromorphs had a high basal metalbolic rate simmilar to that of mammals. academic.oup.com/sysbio/articl… While that doesn't nessacarily mean for ssure that they were endothermic, and the paper raises problems with the idea of the endothermy-ectothermy dichotomy, it certainly makes it a likely proposition. Because of this, in absence of evidence (which I agree the crocodile findings do not qualify as) I think it's certainly possible that basal archosaurs might have devoloped an insulated coating i.e "proto-feathers" to better take advantage of the heat generated. 

Edit: Also, when there's insifficiant evidence either way, it isn't nessacarily more parsimonious to assume a later date for "advanced" features. In fact, the assumption that "feathers" are an advanced feature in archosaurs is just that, an assumption that isn't nessacarily based on anything of worth.
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Albertonykus's avatar
It is of course possible that the hair was lost during taphonomy, or that Lystrosaurus was unusual among therapsids for lacking hair. I didn't say that the specimen definitively shows that dicynodonts didn't have hair, only that it suggests it. I will say that, having seen higher-quality photos of the specimen at conferences and talked to researchers who have examined them firsthand, the details of the skin are fairly well preserved, probably enough to rule out the possibility of matted hair. From what I gather, there are also several such specimens known, which increases the likelihood that it is representative for Lystrosaurus at least.

The evidence for high metabolic rate in stem-archosaurs is interesting, but I wouldn't consider it evidence for filamentous integument on its own. As the authors of the study also point out, inferring thermal strategies from metabolic rate alone is not straightforward and there are many ways to achieve similar thermal strategies. Even if stem-archosaurs were endothermic, we know of extant endotherms that do not require filamentous integument for thermoregulation, such as various fish, leatherback sea turtles, brooding pythons, tegus during breeding season, mammals with sparse hair coverings (including some very small species), etc. (Note that I'm using "endothermic" here to refer to anything that can internally produce a body temperature significantly different from its surroundings.) I certainly wouldn't entirely dismiss the possibility that filaments evolved in stem-archosaurs, but I find it speculative at best.

There is some interesting (unpublished) research by David Lovelace and Scott Hartman modeling Triassic climates and inferring suitable environments for Triassic amniotes under different hypothetical metabolic and integumentary models. Short of finding direct evidence of integument in stem-archosaurs, if Lovelace and Hartman's methods were applied to stem-archosaurs and showed that they would not be able to survive in the climatic conditions they're known from without insulating integument, I would consider that to be more suggestive of the presence of filaments.
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GayCoonie's avatar
You chose a pinniped to repersent living carnivorans. To me, that's repersenting the most asthetically pleasing group of vertibrates with its only ugly subgroup. Of course, you can't please everyone, and I'm amused rather than irritated in any way. I just thought it was a funny thing to point out. This also nicely repersents why calling raccoons rodents makes no sense. It doesn't seem like something anybody would do, but it was constan throughout Guardians of the Galaxy, so obviously some people are that ignorant. This diagram helpfully shows that humans are quite a bit closer to rodents than carnivorans like raccoons are.
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Albertonykus's avatar
I picked a pinniped because I thought it would be most illustrative of the morphological and ecological diversity among carnivorans, and because they're not always acknowledged as carnivorans even in scholarly resources about the group. As you might imagine, the unpredictable aesthetic preferences of my potential audience were at best a secondary point of consideration regarding my choice of taxa, but I'm glad you took it in good humor.

And I concur, it is frustrating how often the term "rodent" is misused.
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CartoonBen's avatar
CartoonBen|Student Digital Artist
Nod Very nice. Magnifying Glass I like how you sorted the animals in that picture.  
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SpongeBobFossilPants's avatar
Ichthyodectiforms aren't osteoglossomorphs anymore?
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Albertonykus's avatar
They haven't been for some time. As far as I'm aware, all actual phylogenetic analyses that include them put them outside of crown-teleosts, and that appears to be the prevailing view.
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benuterf2's avatar
woah, it looks NEAT!
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benuterf2's avatar
No problem
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Crash-the-Megaraptor's avatar
Crash-the-Megaraptor|Hobbyist Traditional Artist
Hey, random question, have you ever heard of the video game "Evolution: The Game of Intelligent Life"?
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TPH-Original's avatar
TPH-OriginalEdited |Hobbyist General Artist
I was reminded of that SNES game "EVO: The Search for Eden". Kind of a cartoony game that doesn't really have any scientific value to it, but it came to mind.
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Albertonykus's avatar
Never. How is it?
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Crash-the-Megaraptor's avatar
Crash-the-Megaraptor|Hobbyist Traditional Artist
I dunno, I've never played it, and it's quite old (like, 1997), but apparently it's a game that allows you to pick an early amphibian and slowly evolve it into various different types of prehistoric animal until you eventually get to intelligent life. From what few videos I've seen, it looks rather cheesy (and obviously accuracy is not entirely what they're going for) but it looks pretty cool and they have a whole lot of creatures nonetheless.

I only really asked because I was reminded of it whilst seeing this guide again.
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Albertonykus's avatar
That's neat! Maybe someday we'll get a really good evolution or history of life game.
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SpongeBobFossilPants's avatar
Has anyone seriously challenged the (Tylopoda(Suina(Cetancodontamorpha, Ruminantiamorpha))) topology for Artiodactyla in recent years? I notice you put them in a polytomy here.
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Albertonykus's avatar
I put them in a polytomy because Holtz put them in a polytomy for the class (maybe from the strict consensus of Spaulding et al., 2009?), but I concur that that looks like the best supported topology for now.
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SpongeBobFossilPants's avatar
Aren't brontotheres stem-perissodactyls (as per Prothero's book)?
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Albertonykus's avatar
At least some analyses support the topology I have here, such as Holbrook and Lapergola (2011).
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anonymous's avatar
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