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Re: Fwd: Are dinosaurs really reptiles? (2)



OK, listen.

I have probably explained this ten times now, spread over the last two or three years, and so have others, but you still don't get it.

To quote-mine Oliver Cromwell, I BESEECH YOU IN THE BOWELS OF CHRIST to open your mind and let the following two points sink in _at long last_.

=== 1) Tree-thinking ===

The tree of life is just that -- a tree --, not a pole.

Branching points on a cladogram are just that: branching points. Points where a _population_ splits into _two_. "Sister" really does mean "sister" and not "mother".

The terminal taxa in a cladogram are just that: terminal. They sit at the _end_ of branches, not at nodes. The nodes are occupied by _reconstructed_ _hypothetical ancestors_, and so is the entire length of all internodes.

=== 2) The nature of the fossil record ===

You know how matter consists almost entirely, _way_ over 99 %, of vacuum, with an atomic nucleus here and there, and with a few electrons thinly smeared all over the place? That's a good metaphor for the fossil record. The fossil record doesn't have a terribly strong systematic bias (within terrestrial tetrapods, that is!!!) -- I've published on this --, but it still consists mostly of absence. _Fossils are extremely rare._ Or rather, fossiliferous sites are extremely rare and much, much poorer than you seem to imagine.

It follows logically that we will more or less _never_ find a direct ancestor of any known species of terrestrial tetrapod older than Miocene perhaps. (To really find ancestors, you have to look at Pliocene _diatoms_ and the like, in other words, at rocks that consist entirely of fossils.) You keep asking for ancestors, and you keep interpreting known taxa as ancestors. Have you still not grasped how naïve this is?!?

===============================

Got that at last? Now to details.

This list, if it is a good one, should follow a gradual evolutionary path with regard to morphology.

Yes, _if_ we had a fossil record that were 25 % complete, as opposed to 0.25 %. (This number comes off the top of my head and may well be several orders of magnitude too _high_.)


--+--Seymouriamorpha
okay. good start. Somewhere outside of Amniota. But where are Gephyrostegus and
Utaherpeton? They're a little more plain and ordinary. Have they been ignored?

Perhaps surprisingly, I agree. The seymouriamorphs are quite far away from Amniota. The lepospondyls are more closely related to the amniotes than the seymouriamorphs are, and so is *Solenodonsaurus*. You'll probably have to wait for my thesis.


|--Diadectomorpha
I'm seeing a pattern here: Small, flat-headed and short-toed gives rise to big,
and short-toed. There's some logic to it. The intertemporal is gone. So this must be an
amniote.Or is it? A fat, slow, plant-eater is the father of us all?

Doesn't *Tseajaia* have an intertemporal? I'll check in a few hours. But anyway, your ignorance shines through. By default ( = by plesiomorphy), diadectomorphs are rather crocodilelike critters, with *Limnoscelis*, *Limnostygis* and *Tseajaia* having conical teeth, and pretty impressive fangs in the maxilla (caniniform teeth!) and premaxilla. Only within Diadectidae we have the very kind of Hennig comb you are looking for: the more closely related to *Diadectes*, the more adaptations to omni- and then herbivory and graviportality.


Things like the astragalus of *Diadectes* are convergent to the amniote condition. *Tseajaia* retains separate tibiale and intermedium.

`--+--Caseidae
The pattern of giant, weird, plant-eaters continues. So it must be true.
No doubt this is an amniote [representing the Synapsida?].

Yes, it represents Theropsida. It's not a bad choice: Caseidae + Eothyrididae together are the sister-group of all other theropsids; the eothyridids are known from a grand total of two isolated skulls, one of which (*Oedalops*) is quite incomplete and the other (*Eothyris*) is not well reconstructed in the literature (I hear work on it is going on right now), while we have fairly complete skeletons of several caseids.


Of course, it would still be better to add ophiacodontids and varanopids. A manuscript that more or less does that (with all varanopids except the most pathetic crumbs) will, hopefully, be submitted soon; I'm its third author.

Where are the plain little insect and meat eaters, like Helosuchus and Westlothiana?
Are we ignoring them because they're not intriguing?

Do you mean *Heleosuchus*? It's a varanopid. That's not just obvious from its recent redescription, but... W4tP. :-) *Westlothiana* is a lepospondyl. Yes, it was reconstructed with diapsid-like peg-shaped supratemporals, but look at the specimen drawing in the same paper: those are ordinary lepospondyl tabulars.


At least the tail is long here. Didn't early reptiles have long tails?

How long?

`--+--+--Mesosauridae
Suddenly we're aquatic! With a decidely long premaxilla! And long teeth!
And a long tail. And a long neck. And long toes! So derived! So early!
This one seems misplaced.

What is this talk about "early"? All three mesosaurs are smack dab in the middle of the Early Permian. Their split from the diapsid line cannot have happened later than the existence of *Hylonomus*, which is near the beginning of the Late Carboniferous. We have lots of time here -- compare whale evolution! Lots of time to acquire autapomorphies, and that's what all characters you list are: autapomorphies -- derived characters that Mesosauridae evolved after having split from its sister-group.


The paper has nice trees _with branch lengths_. The cause for branch length is time. Look at the scale bars.

Oh, yeah, Modesto said it nested with pareaisaurs (not even on the list).

Wait, wait, wait, wait, wait. It's the sister-group of a clade composed of Millerettidae, *Eunotosaurus*, Bolosauridae, Lanthanosuchidae, the "nycteroleters", Procolophonoidea _and_ Pareiasauria.


| `--Procolophonidae
Oh, man. Now we're back to dull teeth, short tail, short toes and a flared skull.
Kinda like Dia
s
Now we're back to long of belly, low to the ground again. With a skull like Gephyrostegus.
Not at all like Procolophon. Not flat-headed.

You deleted at least one line here before sending. But anyway, forget the procolophon_id_s for a moment and look at the other procolophon_oid_s (Owenettidae). Plain vanilla insect eaters all. Herbivorous procolophonoids (Procolophonidae) are no more spectacular than herbivorous lizards.


`--+--+--Thuringothyris and (Captorhinids)
      This one (and its kin) are decidedly flat-headed. Plant eaters.

They all have a fairly strong bite, that's true, but only a part of Captorhinidae was herbivorous. Just look: *Saurorictus*, *Rhiodenticulatus*, *Protocaptorhinus*, *Romeria*, *Concordia*... all have ordinary conical teeth. May have eaten thick-cuticled arthropods.


`--+--Brouffia
I'll have to pass on this one. Not yet in my data base. A pdf would be appreciated.

I doubt there is one, it's a paper from the 1970s. That said, it's the same paper as the descriptions of *Cephalerpeton*, *Coelostegus* and/or *Anthracodromeus* (I don't quite remember), which you seem to have.


`--+--+--Protorothyris
Another close cousin. Say, isn't this fanged taxon getting uncomfortably close to
the Synapsida?

No. As mentioned above, I know what I'm talking about, W4tP.

| |--Anthracodromeus
      [...] That pelvis only has room for on sacral vertebra.

That's interesting, I'll check.

      That means this guy really
      belongs way back there near Seymouria. A reptile imposter!

Are we now doing cladistics with one character? You should be ashamed. All together, *Anthracodromeus* looks just like *Petrolacosaurus*, except for the fact that its skull is anapsid.


BTW, reversals in the number of sacral vertebrae do happen. We have gone through one, related to the size squeeze around the origin of Mammalimorpha. That's why mammalian ilia look so ridiculous.

| `--Cephalerpeton
This guy deserves more respect than he gets. I'm wondering why he appears here,
because he's more like Thuringothyris with that flatish head and those great big dull teeth,
...like, dare I say it... Casea ... way...back...yonder...

Cladistics with _two_ characters now! Woohoo!

It's simply a durophage, with enlarged teeth much like *Araeoscelis*.

`--+--Petrolacosaurus
    Suddenly, after all these 'anapsids' a diapsid!

Where else?

Two holes at once! Isn't it interesting that he
went straight for two, rather than dawdling about with one or the other for awhile?

We have no idea whatsoever if Diapsida went straight for anything or if one of the three* holes came first. That's because of those pesky holes in the fossil record.


Incidentally, *Spinoaequalis* (described as the third araeoscelidian in 1995) would have made a very nice addition. W4tP.

* The suborbital fenestra in the palate.

And that's not all. Long toes. Long limbs. Long neck. Long tail. Sharp teeth. The only taxon
on this list, other than Araeoscelis [and Anthracodromeus] who remotely resembled this one is
Mesosaurus...way... back ...yonder. [shudder]

The mesosaurs are not terribly similar, but *Anthracodromeus* is, and so are *Protorothyris* and *Cephalerpeton*, and so are to a lesser degree *Hylonomus* and *Brouffia*, and to an even lesser degree *Paleothyris*, and to an even lesser degree *Coelostegus*... man, that's precisely what you were asking for! :-) The best part is that this is described at length in the paper, and not even in the online appendices (which I hope you have downloaded and read! -- www.systbiol.org), but in the main text.


this seems to be very scattered famiy tree.

That's because it is. That, in turn, is because of the nature of the fossil record itself.


but the change ought to be gradual. Evolutionary. Not like this see-saw.

Here, both of your fundamental errors apply. First, your failure to appreciate the lack of fossils. Second, you look horizontally across a treetop and complain that you can't see the trunk anywhere.


Next question: What were the five to ten sister genera leading up to Herrerrasaurus? No suprageneric taxa please.

Translation: if we tell you that the fossil record isn't complete enough for that, you will simply refuse to accept that answer. Methinks you haven't thought things through.