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Re: If No. 9 is a hatchling



----- Original Message -----
From: "david peters" <davidrpeters@earthlink.net>
Sent: Friday, September 24, 2004 8:59 PM

> dm:
> Well, if the meanwhile conventional wisdom is right and *Pterodactylus* &
> *Germanodactylus* had a wingspan of some 2.5 m when they were adult (like
> *Pterodactylus longicollum*), then I don't see any problem.
>
> .........Well, you skipped all the candidates that are phylogenetically
closer.

Are they? Or has just PAUP* failed because there are so many
ontogeny-dependent characters in your matrix? -- Well, I'll hopefully find
that out.

> And, forgive me if I'm mistaken, but if you're into conventional wisdom
and you consider P. longicollum the adult, then the little pterodactylids to
their phylogenetic left, some about the same size as No. 9, are they all
hatchlings and juveniles? If so, why do they have extra-long rostra and
small eyes like adults do? Something is illogical here. I would expect a
gradual trend via ontogeny. Not a big leap in 'week two' of their young
lives.

Is this http://www.pterosaurinfo.com/familytree.html still the newest
version of your tree? There's only a "No. 9W" there, and rootward of it I
find a large clade that contains the Maxberg specimen of *Scaphognathus* as
well as *Cycnorhamphus* and *Cearadactylus*.
        Or do you mean to the physical left in
http://www.pterosaurinfo.com/scapho_clade.html?

In any case... yes, I do think none of them is adult. Just _how_ short the
snout of a juvenile is depends not only on its age but also on its
precociality; the more precocial it is, the more adult it looks -- the more
adult it has to look in order to be well adapted to hunting its own food.
Same in tyrannosaurs, sort of -- and in basal birds.

And it's not "week two". It's more like year two.

> Speaking of paedomorphosis, there are dogs with shorter rostra that are
adults. They have shorter rostra than their ancestors. Monkeys have shorter
rostra than lemurs. There are people who look like children but are adults.
They have shorter rostra. You can't be sure a short rostrum is a juvenile
character, especially if the phylogenetic ancestors, in this case the
scaphognathids, also had short rostra. No. 9 just looks like its
grandparents. That's all.

I can be sure that juveniles will have shorter rostra than adults _of the
same LITU_. I can't quantify this a priori; here you are right. Still, it's
enough of a reason to either throw the character out of the matrix, or to
make sure that there are only adults in it!!!

> In scaphognathids the skull stayed pretty much the same in the next
phylogenetic step (No. 9),

In http://www.pterosaurinfo.com/scapho_clade.html the skull of No. 9 is so
small it looks like a crow's. And here
http://www.pterosaurinfo.com/no9.html, even in your tracing, it looks more
like *Pterodactylus* than like *Scaphognathus*.

> but the already diminishing tail diminished further.

"Already diminishing tail" in *Scaphognathus*?

> The proportions of the antebrachium and metacarpus became more equalized.

In http://www.pterosaurinfo.com/scapho_clade.html, both *Scaphognathus* and
*Pterodactylus* have much longer forearms than humeri. No. 9 looks more like
a basal bird in this respect.

> The feet stayed the same, but digit V was less ossified  because its so
small (but it's still there).

If it's there, it's ossified, and if it's not, it's not.

> The trouble is, none of the literature has ever pointed to a good
rhamph/pterodac transition. It's always been a big jump to go from R.
muensteri to P. kochi or Ornithocheirus or you name it. That's old thinking.

Is it? Or is it just a lack of Middle Jurassic fossils -- especially
considering the _general_ lack of MJ land vertebrates? (Remember why
everyone hopes that the Daohugou Fm will really turn out to be MJ as
advertised?)

> Now that problem has been worked out.

We'll see...

> The transitions from protorosaur to pterosaur and from 'rhamphorhynchoid'
to 'pterodactyloid' are as smooth and gradual as in synapsids to mammals.

Sure it is -- but I don't think we have the fossils to fill into this
template.

> Think of it: how do you get a pterodactyloid from a rhamph?
>
> A relatively shorter weaker tail? That's a juvenile character retained in
the adult.

Not quite. In human embryos, the tail never grows very far, but still far
enough that it has to be _actively reduced_ -- like in a tadpole, just less
extremely. More importantly, in this magnitude, it's an _early embryonic_
character, not a juvenile one.

> A relatively shorter antebrachium versus the metacarpus? That's a juvenile
character retained in the adult.

I disagree. Distal elements are expected to be shorter in juveniles, special
cases like horses and antelopes notwithstanding.

> A relatively longer skull relative to the torso? That's a juvenile
character retained in the adult.

Here I agree.

> A relatively smaller naris relative to the skull? That's a juvenile
character retained in the adult.

Here I'd expect the exact opposite.

> David, I sent you the files you'll need to see the complete picture. I'm
here for you.

Unfortunately it'll take some time until I'll be able to have a look at
them. I've only had the first of several exams... there's no chance before
October 8th.

> dp:
> > Your challenge is to match a baby with a mother.
>
> dm:
> Nope. The fossil record is way patchy enough to spare us this challenge.
>
> >>>>>>>
> Hey, you're backing away.

Just like I'd back away from finding a baby for *Istiodactylus*.

> Listen, just find a good sister taxon. I won't be a stickler for every
skeletal detail. But I will insist that the baby, give or take 20%, fit
through the cloaca of the mother you choose.  That's all you have to do.

If this is all, then why don't you accept *Pterodactylus* or
*Germanodactylus*? :-)

> If you can't find a match, you're left with the next most parsimonious
answer: They're different enough to merit separate taxa.

But don't forget that this doesn't mean in any way that No. 9 were adult!

> Don't back down and end up agreeing with me.

Heh heh. That's not likely to happen.