Triassic Mega-Evolution

[Peter Nyikos]

This is a sequel to the thread, "Fabulous Triassic Menagerie" where some
important implications for evolutionary theory of the "menagerie" will be the topic.

The term "mega-evolution" is due to George Gaylord Simpson, an outstanding evolutionary theorist.
It fills a huge gap left by the word "macroevolution" which is often made synonymous
with speciation. A glance at the colorful creatures on the "parent" thread is enough to see
that their evolution went far beyond that.


I have already hypothesized on the "parent" thread that such huge evolutionary
advances are due to an explosion of Punctuated Equilibrium (PE) events:

https://groups.google.com/g/sci.bio.paleontology/c/wivJO-SxPbI/m/yjkSXj7-AAAJ
Re: Fabulous Triassic Menagerie
Sep 27, 2023, 9:52:50 PM

In my next post to this thread, I will be speculating on another possibility that would come under mega-evolutionary theory.


Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
http://people.math.sc.edu/nyikos

[Peter Nyikos]

This is a reply to a post by Sight Reader on the thread, ""Fabulous Triassic Menagerie".

On Monday, September 25, 2023 at 3:37:06 PM UTC-4, Sight Reader wrote:
> On Monday, September 25, 2023 at 9:26:21 AM UTC-6, erik simpson wrote:
> > On Sunday, September 24, 2023 at 8:12:23 AM UTC-7, Sight Reader wrote:
[...]
> > > > > On Friday, September 22, 2023 at 6:43:12 PM UTC-7, Peter Nyikos wrote:

> > > > > > I've long been familiar with some strange critters of the Triassic, but I was
> > > > > > really amazed at the variety that was displayed for us by Gary Meany, in Quora, of all places:
> > > > > > https://www.quora.com/What-is-the-most-interesting-period-in-the-ancient-history-of-Earth-Is-it-the-Triassic-the-Jurassic-the-Cambrian-the-Devonian-or-other/answer/Gary-Meaney

> > > > > >
> > > > > > He starts out:
> > > > > > "It’s like choosing a favourite child, honestly, but I think I’ll go with the Triassic for today. This period started about 251 million years ago, immediately preceded by the infamous End-Permian Extinction - the most devastating extinction event in Earth’s history.
> > > > > >
> > > > > > "The cause of this mass extinction, also known as the Great Dying, is debated, but we do know it was immensely lethal. It’s thought that nearly 60% of all biological families were wiped out, including 70% of the world’s land vertebrate species. What this means is that, entering the Triassic, evolution practically had a clean slate to experiment with."
> > > > > >
> > > > > >
> > > > > > Then the fun begins: one unusual animal after another, each one with a well-executed color picture.


<big snip for focus>


> > > What little I know I got from the Sues/Fraser book “Triassic Life on Land”. At maybe 20 years old, it’s already aging rapidly thanks to today’s ridiculous pace of discoveries.

> > The Paleocene resembles the Triassic with respect to the appearance of weird beasts that don't last
> > long in the evolutionary sense. For that matter, the same can be said for any rapid expansion into
> > new or recently vacated ecospace. The first arrivals in new territory got out of the blocks fast, but
> > may not be particularly well-adapted to conditions.

<small snip>

> Certainly a lot of these guys fall under the “fast-but-inefficient” category;

Would you like to give us some examples that you found particularly striking, and why?


>however, we also have that end-Triassic extinction that may have wiped out a lotta guys that were doing perfectly well.

You came across a superfamily, *Allokotosauria*, that went extinct somewhere along the line,
and I came across another, *Poposauroidea*, after finding a Spinosaurus/Dimetrodon look-alike
that was in the comments section of the Quora article linked above.

It would be very interesting to know when and why such big clades went extinct.
We could try chasing down all the critters in these clades for some clue as to whether any
were still hanging on at or near the end of the Triassic. But if that fails, the problem could
be the fault of what you wrote next:

> From what I recall, our Triassic information is so sparse that it would be hard to tell exactly how long some of these weird experiments persisted.

There is at least one example of mega-evolution where the extinctions were due
to competition between two huge clades: Pterosauria and Avialae. At the beginning
of the Cretaceous, there were many kinds of small pterosaurs. Near the end,
at the Upper Maaristrichtian, there was only one pterosaur whose wingspread
was less than 2 meters, while ALL known birds were 2 meters or less, and there
were *many* genera of pterosaurs at 4 or (many!) more meters.

The upshot is that the usual definition of "natural selection," competition
*within* *populations*, completely misses such major events. This was
mega-competition, and the Triassic might give us quite a few other examples.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

Univ. of South Carolina at Columbia
http://people.math.sc.edu/nyikos

[Sight Reader]

On Thursday, September 28, 2023 at 11:52:15 AM UTC-6, Peter Nyikos wrote:
> This is a reply to a post by Sight Reader on the thread, ""Fabulous Triassic Menagerie".
>

> <big snip for focus>

> > Certainly a lot of these guys fall under the “fast-but-inefficient” category;
> Would you like to give us some examples that you found particularly striking, and why?

To be clear, the comment I made about “fast but inefficient” was in support of the following remark by Mr. Simpson:

> For that matter, the same can be said for any rapid expansion into new or recently vacated ecospace. The first
> arrivals in new territory got out of the blocks fast, but may not be particularly well-adapted to conditions.

To me, a possible example of what Mr. Simpson was referring to would be the attempt by temnospondyls to secure the “top swamp predator spot” during the Triassic. I don’t know how important temnospondyls were back in the Permian, but they certainly seemed to jump all over the early Triassic when little else appeared to be left in the swamp. As the Triassic wore on, though, it seems as if various archosaurs - most notably phytosaurs - pushed them off the dominant role and started diminishing them, after which they were dealt a crippling blow by the T-Jr extinction.

Does this mean I am claiming that I know “for a fact” that archosaurs came in and competed for the exact same niche that temnospondyls had, that archosaurs and their hard eggs were provably “more efficient” than the amphibians, and that archosaurs were the direct cause for their decline? Of course not: its hard enough to figure out how anyone’s niche actually interacted with others, never mind determining the real reasons why any particular clade may have declined.

The same could be said for Lystrosaurus, those squat dicynodonts who “ruled the earth” (or at least the dry parts of it) for a few million years while everyone else was wiped out. Starting from complete dominance, we then see dicynodonts dwindle to increasingly smaller and more specialized roles; however, as with temnospondyls, it’s hard to establish the exact details of “who”, “why”, or “how”.

> It would be very interesting to know when and why such big clades went extinct.
> We could try chasing down all the critters in these clades for some clue as to whether any
> were still hanging on at or near the end of the Triassic. But if that fails, the problem could
> be the fault of what you wrote next:
>
> > From what I recall, our Triassic information is so sparse that it would be hard to tell exactly how long some of these weird experiments persisted.

Well, in addition to the difficulties mentioned above in nailing down the true causes of decline, I find that there’s another problem with the Triassic in that it has a confounding number of transitional species. When they give us something as enigmatic as - say - the “aphanosaurs”, it becomes really hard to tell if they were one of these outcompeted “fast and inefficient” guys like Mr. Simpson proposed or if they were a transitional phase of something that shows up later in a more derived form. Really hard to say much about such clades when the entire world has produced only a few fragments of them.

> There is at least one example of mega-evolution where the extinctions were due
> to competition between two huge clades: Pterosauria and Avialae. At the beginning
> of the Cretaceous, there were many kinds of small pterosaurs. Near the end,
> at the Upper Maaristrichtian, there was only one pterosaur whose wingspread
> was less than 2 meters, while ALL known birds were 2 meters or less, and there
> were *many* genera of pterosaurs at 4 or (many!) more meters.
>

Well, my knowledge is not as encyclopedic as yours, but the battle you relate reminds me of the epic battle between rhynchocephalians and today’s lizards. Those two clades seem to consist of guys that seemingly look and act alike and had an endless tug-of-war starting from back in the Triassic, where one could only seem to rise to dominance at the direct expense of the other. I think there’s only one rhynchocephalian left off of New Zealand somewhere.

It bears reiterating, though - I find it very dangerous to assume any of the wacky and weird animals running around towards the end of the Triassic (drepanosaurs, aetosaurs and the like) disappeared because they were in the “fast and inefficient” category when there’s a mass extinction looming. For all we know, such weirdos may have been on the verge of explosive dominance had not the wrath of the T-Jr extinction swept them from the stage.

[erik simpson]

Some of the giant Triassic temnospondyls have been described as "toilet seats with teeth", a very scary idea. Actually,
they probably occupied a niche since filled by alligators and crocodiles, but these came much later. They actually lasted
into the early Cretaceous, so they weren't really bad adapted for the job. But for the end-Triassic extinction, a fair number
of the early Triassic beasts may have stayed in the race. Dinosaurs didn't really "take over" until the Juirassic.

BTW, you could drop the "Mr. Simpson" address. I haven't been called that since grad school except by insurance agents
and the like. It's actually Dr. Simpson, but that's even worse. "Erik" is fine. I've been called that all my life.

[Sight Reader]

On Friday, September 29, 2023 at 9:39:24 AM UTC-6, erik simpson wrote:
<snip for brevity>

> Some of the giant Triassic temnospondyls have been described as "toilet seats with teeth", a very scary idea. Actually,
> they probably occupied a niche since filled by alligators and crocodiles, but these came much later. They actually lasted
> into the early Cretaceous, so they weren't really bad adapted for the job. But for the end-Triassic extinction, a fair number
> of the early Triassic beasts may have stayed in the race. Dinosaurs didn't really "take over" until the Juirassic.
>

Thanks for the great info, Doc Simpson! I totally agree: in many ways, it seemed like that the Triassic had just started to really get going with the battle between the dominant crocodylomorphs, the rising dinosaurs, what was left of the synapsids, and a lot of strange and exciting new archosauromorphs when that T-Jr event shut everything down.

It also looked like, by the late Triassic (which is pretty much HALF of it), there was some pretty lively competition between phytosaurs and temnospondyls. If I recall correctly, temnospondyls were less likely to completely control swamps as much as they did right after the P-T event. From what I read, it seemed like phytosaurs were pretty darn successful by the end-Triassic; I find myself wondering if crocodylomorphs would have had any sort of shot at that niche if it weren’t for the Tr-J event…

[Peter Nyikos]

You've given me a lot to think about over the weekend, Sight Reader.

Time constraints keep me from saying much now: we have what we jokingly call
a "Fluid Dynamics Seminar" where math grad students and a few faculty
meet on Fridays in a bar or restaurant and drink/eat/play board games/watch others play them.
In fact it started a minute after I started typing this. So I'll be somewhat late, but
that's OK. Despite the word "Seminar", we are very informal, but some people do
get into conversations which sometimes get deep and intense, and not just about math.
No matter how intense they get, the camaraderie has never soured.

Yup, *Sphenodon,* the tuatara. I've seen one in captivity. I'm told they rival giant tortoises
in longevity. So far, trying to introduce them to the mainland [the North Island] have been
failures. There are plenty of offshore islands, and they seem to be doing fine on Little Barrier Island.

That island is a very strict nature preserve. Only people with excellent environmental
credentials are given permission to set foot there. There is a good friend of mine who is
a long-time researcher in U. of Auckand (now emeritus) in one of my specialties
who has that permission, yet even he is restricted from some areas
that are outside his documentable credentials.

>
> It bears reiterating, though - I find it very dangerous to assume any of the wacky and weird animals running around towards the end of the Triassic (drepanosaurs, aetosaurs and the like) disappeared because they were in the “fast and inefficient” category when there’s a mass extinction looming. For all we know, such weirdos may have been on the verge of explosive dominance had not the wrath of the T-Jr extinction swept them from the stage.

TGIF,

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

Univ. of South Carolina in Columbia
http://people.math.sc.edu/nyikos

[Peter Nyikos]

On Friday, September 29, 2023 at 11:39:24 AM UTC-4, erik simpson wrote:

> Some of the giant Triassic temnospondyls have been described as "toilet seats with teeth", a very scary idea.

That's because they were incredibly flattened, like Gerrothorax in the Quora article I linked in the OP.
Otherwise, they were most like angler fish, which have even more formidable looking teeth.

> Actually,
> they probably occupied a niche since filled by alligators and crocodiles, but these came much later.

IIRC the heyday of the temnospondyls was the Carboniferous. In the Permian, they were
already under attack by synapsids; Dimetrodon was one top predator, barring the bigger ones
from much of the dry land.

> They actually lasted
> into the early Cretaceous, so they weren't really bad adapted for the job.

They were, however, a rather specialized lot. Modern day amphibians are generally
believed to be descended from them, but there are other opinions held by many
paleontologists, including the one that frogs descended from temnospondyls,
while salamanders and caecilians were lepospondyls.

>But for the end-Triassic extinction, a fair number
> of the early Triassic beasts may have stayed in the race. Dinosaurs didn't really "take over" until the Juirassic.
>
> BTW, you could drop the "Mr. Simpson" address. I haven't been called that since grad school except by insurance agents
> and the like. It's actually Dr. Simpson, but that's even worse. "Erik" is fine. I've been called that all my life.

You reminded me of an incident in soc.history.medieval ca. 1998, where some newcomer complained
about people being disrespectful by not calling me Dr. Nyikos or Prof. Nyikos. One of the more
hostile women there said that I'm lucky if I'm called "Mr. Nyikos."

In reply, I paraphrased a beer commercial that had been popular two and a half decades earlier:

"You can call me `Pete,' you can call me `Peter', you can call me `Nyikos';
but you *doesn't* hafta call me `Mr. Nyikos'."

The bad grammar is from the commercial, which featured a yokel talking that way
about a brand of beer whose name ended with "Natural Light". The message was that
"Natural" was quite adequate for identification.

Peter Nyikos
Professor, Dept. of Mathematics

Univ. of South Carolina -- standard disclaimer--
http://people.math.sc.edu/nyikos

[erik simpson]

You probably meant that crown amphibians are descended from lepospondyls. Paleontological consensus
is that temnospondyls are stem lissamphibians. https://en.wikipedia.org/wiki/Temnospondyli

[Peter Nyikos]

These last two weeks I've been terribly busy, and today is no exception,
but this hour before my office hours is the "eye of the storm,"
and I only expect the storm to hit again in earnest when I go home from the office around
4pm and start composing the test that I give one of my courses on Friday.

On Thursday, September 28, 2023 at 10:51:47 PM UTC-4, Sight Reader wrote:
> On Thursday, September 28, 2023 at 11:52:15 AM UTC-6, Peter Nyikos wrote:
> > This is a reply to a post by Sight Reader on the thread, ""Fabulous Triassic Menagerie".
> >
> > <big snip for focus>
> > > Certainly a lot of these guys fall under the “fast-but-inefficient” category;

> > Would you like to give us some examples that you found particularly striking, and why?

> To be clear, the comment I made about “fast but inefficient” was in support of the following remark by Mr. Simpson:
> > For that matter, the same can be said for any rapid expansion into new or recently vacated ecospace. The first
> > arrivals in new territory got out of the blocks fast, but may not be particularly well-adapted to conditions.

> To me, a possible example of what Mr. Simpson was referring to would be the attempt by temnospondyls to secure the “top swamp predator spot” during the Triassic. I don’t know how important temnospondyls were back in the Permian, but they certainly seemed to jump all over the early Triassic when little else appeared to be left in the swamp.

What else was in the swamp before? There were a lot of lepospondyls, and I'll have to
review things later this week to see how they fared in the Triassic, or the Permian for that matter.

As for the Permian and Triassic amniotes, I didn't think of them as swamp critters.
Do you have any indication that the Permian ones played a big swamp role?
Their ancestors appeared well back in the Carboniferous, and I'll have to check
on them too this weekend.

>As the Triassic wore on, though, it seems as if various archosaurs - most notably phytosaurs - pushed them off the dominant role and started diminishing them, after which they were dealt a crippling blow by the T-Jr extinction.

Don't forget about the synapsids. There were some carnivorous ones all through
the Permian and the Triassic. The Triassic was dominated by the carnivorous
therocephalians and the cynodonts, among whom the iconic *Cynognathus* was
a predator. The cynodonts also included *Thrinaxodon*, a genus used as the moniker
of a former sci.bio.paleontology regular, who almost destroyed s.b.p. by spam
before reinventing herself as Oxyaena, after having cleaned up that part of her act.

The therapsid original was a small predator:

"Thrinaxodon was a small synapsid roughly the size of a fox[1] and possibly covered in hair. The dentition suggests that it was a carnivore, focusing its diet mostly on insects, small herbivores and invertebrates."
--https://en.wikipedia.org/wiki/Thrinaxodon

> Does this mean I am claiming that I know “for a fact” that archosaurs came in and competed for the exact same niche that temnospondyls had, that archosaurs and their hard eggs were provably “more efficient” than the amphibians, and that archosaurs were the direct cause for their decline? Of course not: its hard enough to figure out how anyone’s niche actually interacted with others, never mind determining the real reasons why any particular clade may have declined.

The synapsids were decimated by the end of Triassic extinction,
but were doing rather well before that:

"Eutheriodontia is a clade of therapsids which appear during the Middle Permian and which includes therocephalians and cynodonts, this latter group including mammals and related forms.

"With the dicynodonts, they form one of two lineages of therapsids that survived the End-Permian extinction and which diversified again during the Triassic, before the majority of them disappeared before or during the Triassic–Jurassic extinction, except for a lineage of cynodonts that would later give rise to mammals."

https://en.wikipedia.org/wiki/Eutheriodontia

>
> The same could be said for Lystrosaurus, those squat dicynodonts who “ruled the earth” (or at least the dry parts of it) for a few million years while everyone else was wiped out. Starting from complete dominance, we then see dicynodonts dwindle to increasingly smaller and more specialized roles; however, as with temnospondyls, it’s hard to establish the exact details of “who”, “why”, or “how”.

> > It would be very interesting to know when and why such big clades went extinct.
> > We could try chasing down all the critters in these clades for some clue as to whether any
> > were still hanging on at or near the end of the Triassic. But if that fails, the problem could
> > be the fault of what you wrote next:
> >
> > > From what I recall, our Triassic information is so sparse that it would be hard to tell exactly how long some of these weird experiments persisted.

> Well, in addition to the difficulties mentioned above in nailing down the true causes of decline, I find that there’s another problem with the Triassic in that it has a confounding number of transitional species. When they give us something as enigmatic as - say - the “aphanosaurs”, it becomes really hard to tell if they were one of these outcompeted “fast and inefficient” guys like Mr. Simpson proposed or if they were a transitional phase of something that shows up later in a more derived form.

Excellent point.

>Really hard to say much about such clades when the entire world has produced only a few fragments of them.

Agreed.

> > There is at least one example of mega-evolution where the extinctions were due
> > to competition between two huge clades: Pterosauria and Avialae. At the beginning
> > of the Cretaceous, there were many kinds of small pterosaurs. Near the end,
> > at the Upper Maaristrichtian, there was only one pterosaur whose wingspread
> > was less than 2 meters, while ALL known birds were 2 meters or less, and there
> > were *many* genera of pterosaurs at 4 or (many!) more meters.
> >
> Well, my knowledge is not as encyclopedic as yours, but the battle you relate reminds me of the epic battle between rhynchocephalians and today’s lizards. Those two clades seem to consist of guys that seemingly look and act alike and had an endless tug-of-war starting from back in the Triassic, where one could only seem to rise to dominance at the direct expense of the other.

This looks very promising, but it will take me quite a while to get really
well-informed about this. My first impression is that lizards really
started to take off in the Cretaceous, followed by a big explosion after the K-P extinction.
But the Triassic and the Jurassic might have seen some real competition.


Thank you for commenting in such detail. It got me looking up a whole bunch
of things that I was only dimly aware of before, including a lot of what I
wrote about above. This is the kind of interaction s.b.p. needs now,
what with so little participation by professionals.

Back in the 1990's it was a whole other scene. You may have heard
of Thomas Holtz, a great popularizer of dinosaurs. He was a regular
participant back then.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

University of South Carolina
https://people.math.sc.edu/nyikos

[Sight Reader]

Thanks for the really fun and interesting comments!

On Wednesday, October 4, 2023 at 12:35:53 PM UTC-6, Peter Nyikos wrote:

<snip because I don’t know any better>

> What else was in the swamp before? There were a lot of lepospondyls, and I'll have to
> review things later this week to see how they fared in the Triassic, or the Permian for that matter.
>
> As for the Permian and Triassic amniotes, I didn't think of them as swamp critters.
> Do you have any indication that the Permian ones played a big swamp role?

I have an absolutely ZERO idea. The book I read (Sues-Fraser) didn’t cover Permian assemblages at all, meaning that I am utterly helpless when it comes to the Permian “Age of Synapsids”. The book only brought up the Permian when it happened to talk about one or two species that had ancestors from the Permian.

> Their ancestors appeared well back in the Carboniferous, and I'll have to check
> on them too this weekend.
> >As the Triassic wore on, though, it seems as if various archosaurs - most notably phytosaurs - pushed them off the dominant role and started diminishing them, after which they were dealt a crippling blow by the T-Jr extinction.
> Don't forget about the synapsids. There were some carnivorous ones all through
> the Permian and the Triassic. The Triassic was dominated by the carnivorous
> therocephalians and the cynodonts, among whom the iconic *Cynognathus* was
> a predator. The cynodonts also included *Thrinaxodon*, a genus used as the moniker
> of a former sci.bio.paleontology regular, who almost destroyed s.b.p. by spam
> before reinventing herself as Oxyaena, after having cleaned up that part of her act.

Without doubt! What I utterly failed to reiterate (and thus created confusion) was that I was talking about the SWAMP ecosystem in particular, which didn’t appear to have many synapsid predators. Conversely, neither temnospondyls nor phytosaurs seemed to wander far from the swamp - at least based on the assemblages Sues and Fraser listed - which makes perfect sense for the temnospondyls (eggs too mushy for dry land!) but is a more intriguing limitation for phytosaurs. Other archosaurs, of course, were able to move out from the swamp and take on cynodonts and other synapsid predators on dry land.

They didn’t mention any swamp assemblages that seemed at all dominated by synapsid predators. I suppose it would make sense that (furry?) guys like Thrinaxodon and Cynognathus would have no interest in mixing it up with the submerged monsters of the swamp, but the big, tough dicynodont herbivores definitely wandered in from time to time and show up in a few assemblages.

> The synapsids were decimated by the end of Triassic extinction,
> but were doing rather well before that:

From what I read, it may be that synapsids weren’t doing badly just before the T-Jr extinction, but on the other hand they didn’t seem to be going absolutely gangbusters like the crocodylomorphs and the dinosaurs were. You still had a few big cats like Exaeretodon and herds of big dicynodonts like Placieras working the more spectactular niches, but most of the others synapsids seemed to have retreated into the smaller rodent or weasel roles, where a lot of change and variety seemed to be emerging as some started to transition towards mammals.

> This looks very promising, but it will take me quite a while to get really
> well-informed about this. My first impression is that lizards really
> started to take off in the Cretaceous, followed by a big explosion after the K-P extinction.
> But the Triassic and the Jurassic might have seen some real competition.

I actually don’t know. I was basically quoting an author somewhere who mentioned this tug-of-war that was to follow between lizards and rhynchocephalians, but I don’t know the details of who dominated when: I only know that rhynchocephalians were in charge first and lizards last.

[Peter Nyikos]

As usual, my various commitments [many having to do with a test I gave one class and another
that I'll give on Monday] have left me with very little time for posting this week.
This is the only s.b.p. post I can do before going on my usual weekend posting break.

On Tuesday, October 3, 2023 at 7:06:12 PM UTC-4, erik simpson wrote:
> On Tuesday, October 3, 2023 at 12:18:04 PM UTC-7, Peter Nyikos wrote:
> > On Friday, September 29, 2023 at 11:39:24 AM UTC-4, erik simpson wrote:
> >
> > > Some of the giant Triassic temnospondyls have been described as "toilet seats with teeth", a very scary idea.
> > That's because they were incredibly flattened, like Gerrothorax in the Quora article I linked in the OP.

This was a mild senior moment. The OP where I linked that Quora article was in the other recent
thread, "Fabulous Triassic Menagerie." Here is a link to the article itself:

https://www.quora.com/What-is-the-most-interesting-period-in-the-ancient-history-of-Earth-Is-it-the-Triassic-the-Jurassic-the-Cambrian-the-Devonian-or-other/answer/Gary-Meaney

> > Otherwise, they were most like angler fish, which have even more formidable looking teeth.
> > > Actually,
> > > they probably occupied a niche since filled by alligators and crocodiles, but these came much later.
> > IIRC the heyday of the temnospondyls was the Carboniferous. In the Permian, they were
> > already under attack by synapsids; Dimetrodon was one top predator, barring the bigger ones
> > from much of the dry land.

> > > They actually lasted
> > > into the early Cretaceous, so they weren't really bad adapted for the job.

> > They were, however, a rather specialized lot. Modern day amphibians are generally
> > believed to be descended from them, but there are other opinions held by many
> > paleontologists, including the one that frogs descended from temnospondyls,
> > while salamanders and caecilians were lepospondyls.

By "them" I meant some temnospondyls, but not the ones that survived into the Jurassic.

> > >But for the end-Triassic extinction, a fair number
> > > of the early Triassic beasts may have stayed in the race. Dinosaurs didn't really "take over" until the Juirassic.

<snip to get to your latest words>

> You probably meant that crown amphibians are descended from lepospondyls.

No, I was just grabbing a few hypotheses that I have encountered over the years.
The actual phylogeny of early amphibians is a god-awful mess of competing hypotheses.
The "split ancestry" of lissamphibians (crown group amphibians) that I mentioned above
is the one endorsed by Romer, Colbert, and even Carroll (1988).

> Paleontological consensus
> is that temnospondyls are stem lissamphibians. https://en.wikipedia.org/wiki/Temnospondyli

Did you not see the second cladogram on that webpage, which makes them out to be descended
from lepospondyls? That's exactly what you thought I meant to say (see above) --
but then, why did you make this last comment?


Peter Nyikos

Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina

https://people.math.sc.edu/nyikos

[erik simpson]

The second cladogram shows Lissamphibians and Temnospodyls (both within lepospondyla) are sister groups,
of which temnospondyls are extinct. Frogs are not descended from temnospondyls, although some in the past
postulated that they may be. Pre-1990 phylogenies are no longer "consensus phyulogeny".

[Peter Nyikos]

Neither of the two cladograms with pictures put temnospondyls anywhere near lepospondyls.
.
You seem to be outdoing me in senior moments on this thread. :-\

> Frogs are not descended from temnospondyls, although some in the past
> postulated that they may be.

I was using a little common sense: given their evolutionary history,
the LCA of lissamphibians and temnospondyls must have been much
more like a temnospondyl than a lissamphibian.

A few years ago, we had a similar divergence of opinion about
Ctenophora, and then John even agreed that the LCA of sponges
and ctenophores probably resembled a sponge.

> Pre-1990 phylogenies are no longer "consensus phyulogeny".

Because they (including Carroll, 1988) did not rely exclusively on cladistic analyses?

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

University of So. Carolina at Columbia
http://people.math.sc.edu/nyikos

[erik simpson]

There are several cladograms; look at the second.
Ctenophores have nothing to do with this. Why you're dredging this up is unclear. Whether or
not something "looked like" is irrelevant to the DNA analysis, which is vwery difficult in this
case.

Cladistic analysis has little to do with it, DNA analysis has everything to do with it. All crown amphibians
are lissamphibians.

[John Harshman]

Cladistic analysis is an ambiguous term, but I would say that most DNA
analyses are cladistic in some reasonable sense. Further, there can be
no DNA analysis to test the relationships of amphibians to extinct taxa.
Only fossil data can do that. All we can tell from DNA is that
amphibians are a clade relative to amniotes.

[Peter Nyikos]

> > > > > > > of the early Triassic beasts may have stayed in the race. Dinosaurs didn't really "take over" until the Jurassic.

> > > > <snip to get to your latest words>

> > > > > You probably meant that crown amphibians are descended from lepospondyls.

> > > > No, I was just grabbing a few hypotheses that I have encountered over the years.
> > > > The actual phylogeny of early amphibians is a god-awful mess of competing hypotheses.
> > > > The "split ancestry" of lissamphibians (crown group amphibians) that I mentioned above
> > > > is the one endorsed by Romer, Colbert, and even Carroll (1988).

> > > > > Paleontological consensus
> > > > > is that temnospondyls are stem lissamphibians. https://en.wikipedia.org/wiki/Temnospondyli

> > > > Did you not see the second cladogram on that webpage, which makes them out to be descended
> > > > from lepospondyls? That's exactly what you thought I meant to say (see above) --
> > > > but then, why did you make this last comment?

<crickets>

> > > The second cladogram shows Lissamphibians and Temnospodyls (both within lepospondyla) are sister groups,
> > > of which temnospondyls are extinct.

> > Neither of the two cladograms with pictures put temnospondyls anywhere near lepospondyls.
> > .
> > You seem to be outdoing me in senior moments on this thread. :-\

Either that, or you are trolling by making one "mistake" after another.

> > > Frogs are not descended from temnospondyls, although some in the past
> > > postulated that they may be.

> > I was using a little common sense: given their evolutionary history,
> > the LCA of lissamphibians and temnospondyls must have been much
> > more like a temnospondyl than a lissamphibian.
> >
> > A few years ago, we had a similar divergence of opinion about
> > Ctenophora, and then John even agreed that the LCA of sponges
> > and ctenophores probably resembled a sponge.

> > > Pre-1990 phylogenies are no longer "consensus [phylogeny]".

> > Because they (including Carroll, 1988) did not rely exclusively on cladistic analyses?

> There are several cladograms; look at the second.

I did, but you either did not, or you have been trolling these last two rounds
by deliberately posting false information to get my dander up.

And at this point you may be thinking, "Ha-Ha! Made you look!"

> Ctenophores have nothing to do with this. Why you're dredging this up is unclear.

It should be clear to anyone with a serious interest in scientific research.
Competent researchers are on the lookout for general phenomena that
tie together specific observations which have a lot in common.

It is in the realm of polemic (specifically, secondary school debating conventions)
that it is a criticism that one is straying from the topic. This is a science "newsgroup,"
and it isn't supposed to be as saturated with polemic as talk.origins.

And your past behavior shows that your heart is in the atmosphere of talk.origins
whenever you deal with me. It's been that way since mid-2017, when Richard Norman
stopped posting to both groups.

> Whether or
> not something "looked like" is irrelevant to the DNA analysis,

I was using the sophisticated version of "looked like," which takes into
account internal anatomy as well as external appearances.
With extinct animals, we need to focus on the former, although
really competent reproductions do give some clue to internal anatomy.

> which is vwery difficult in this
> case.
>
> Cladistic analysis has little to do with it, DNA analysis has everything to do with it. All crown amphibians
> are lissamphibians.

BY DEFINITION!! How typical of you to obscure that fact.

What other DNA analyses do evolutionary biologists use, besides those
following cladistic methods like MP, ML, and NJ? Molecular clocks are
generally considered to be a poor substitute.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos

[erik simpson]

My mistake. I should have said the first cladogram. The relationship of Temnospondlys and LIssamphibia
is clear. You're letting past problems inflame you. I'm through with this thread.

[Peter Nyikos]

<crickets>

> My mistake. I should have said the first cladogram.

That doesn't help. The issue was and still is the following:

[repeated from above, with you going first:]

> > > > > The second cladogram shows Lissamphibians and Temnospodyls (both within lepospondyla) are sister groups,
> > > > > of which temnospondyls are extinct.
> >
> > > > Neither of the two cladograms with pictures put temnospondyls anywhere near lepospondyls.
> > > > .
> > > > You seem to be outdoing me in senior moments on this thread. :-\

[end of quote]

> The relationship of Temnospondlys and LIssamphibia
> is clear.

This much was clear from the beginning. It is the part in parentheses
"(both within lepospondyla)" that you're repeatedly ignoring along
with my reply "Neither of the two cladograms..."

>You're letting past problems inflame you.

The main problem is in the immediate past, and you've doubled down on it.

> I'm through with this thread.

Naturally: you wouldn't want to triple down on your incomprehensions, which
you can't seem to cure yourself of.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

Univ. of South Carolina at Columbia
http://people.math.sc.edu/nyikos

PS Methinks this will be one of many posts which your pal John Harshman
"cannot see because he doesn't want to see it."

[erik simpson]

<clip for focus>

Neither Temnospodyls nor Lissamphibians are Lepospondyls.
Temnospondyls and Lissamphibians are sister groups.
Temnospondyls are extinct.
Crown amphibians are LIssamphibians.

If you want further elucidations, talk to the hand.

[Peter Nyikos]

On Monday, October 30, 2023 at 4:30:55 PM UTC-4, erik simpson wrote:

> <clip for focus>

...away from your three mistakes, the first of which is qualified, the other two are not..

(1) "You probably meant that crown amphibians are descended from lepospondyls."

(2) "The second cladogram shows Lissamphibians and Temnospodyls (both within lepospondyla) are sister groups"

(3) "My mistake. I should have said the first cladogram."

> Neither Temnospodyls nor Lissamphibians are Lepospondyls.

Thanks for implicitly acknowledging your two latter mistakes, due to
the parenthetical "both within lepospondyla".

I'm giving you the benefit of the doubt: I'm assuming that
you are NOT following a polemical convention that
"If I, Erik Simpson, do not admit to having made a mistake on Usenet,
I cannot be nailed on having made a mistake on Usenet."


<snip of three things which are irrelevant to the three mistakes>

>
> If you want further elucidations, talk to the hand.

HAND.


Peter Nyikos