Re: Rahonavis....Both!

["John V Jackson" <jjackson@interalpha.co.uk>]

--Original Message-- From: T. Mike Keesey <tkeese1@gl.umbc.edu>To: Larry
Febo <larryf@capital.net>Cc: dinosaur@usc.edu : Wednesday, February 24, 1999
06:51 PM

[snip]

>Dromaeosaurids are "advanced" in that they have new features not found in
>the ancestral eumaniraptor. If, by "advanced", you mean, "sharing more
>recent ancestry with modern birds", and are suggesting this tree:
>
>|--_Archaeopteryx_
>+--+--_Rahonavis_
>   |--Dromaeosauridae
>   +--advanced birds
>
>Then I'd like to hear what evidence backs this up.

Try...  http://www.geocities.com/CapeCanaveral/Hall/2099/DinoKabin.html

...though I don't think you will like it!  :-)


[LF] >> So, it doesn`t seem to fit in as a decent intermediate either.
>
>No,

Yes!  It's a perfect intermediate - except in terms of time, which is not
significant.

>but it's probably a relatively unmodified (at least, the parts we
>have of it are relatively unmodified -- [snip]) descendant of an
> intermediate between basal eumaniraptors and basal avians.

But that intermediate might well be early, so it could have evolved quite
early.  Yet in statement B below you place some importance on its likelihood
of evolving late.


But if it were a descendant of an intermediate between basal eumaniraptors
and basal avians (I assume 'basal avians' means the first birds), Rahonavis
would have evolved flight independently... unless you believe R. was
pre-flying.

(It won't be long before we get widespread advocation of multiple
independent evolution of flight events!)




>
>> More likely further advanced because it actually had
>> more time to evolve into the Cretaceous, and give rise to Dromaeosaurs.
>
>I fail to see how _Rahonavis_ could have given rise to dromaeosaurids when
>
>A) It shares no synapomorphies with them that are not basic eumaniraptoran
>synapomorphies.

The second toe's hyperextensibility may have been a basic
eumaniraptoran synapomorphy; the *large* hooked claw was not.  But
statement A (even if eventually demonstrated) wouldn't prevent Raho. >
droms. anyway.


>
>B) It's from the very end of the Cretaceous, and dromaeosaurids are known
>from the Early Cretaceous (and possibly the Jurassic).

It's good to see some value placed on stratigraphy, but don't let your
co-theorists read this!   I wouldn't put too much weight on a single
ocurrence though, particularly when the specimen is small, and two other
sickle claws survived 80mys.


...and...


--Original Message-- From: Thomas R. Holtz, Jr. To: larryf@capital.net Cc:
dinosaur@usc.edu : Wednesday, February 24, 1999 06:51 PM



>At 10:52 AM 2/24/99 -0500, Larry Febo wrote:
>
>>Well, yeah, but...I`ve been hearing lately (sorry no specific refs) that
>>Dromaeosaurs seem in many ways MORE advanced than Archeopteryx, and for
>> that matter,...so is Rahonavis.
>
>Wish you could provide the refs to back this up.

As you suggested in an earlier post, ulna:femur:-  Rahonavis >1.5;
Archaeopteryx approx 1.  And the feather bumps only on R's ulna.

>From the original Forster et al (Science 20/March/98 pp1915-1919), the
picture of the scapula shows R. to have a significantly more flight-advanced
acromium process than Archae.  The camellate (saddle shaped) cervicodorsal
vertebra places R. intermediate between both Ax and droms, and Ax and birds.

(Features that place R. closer to droms than Ax is:
Tibia:MT IV:  Ax: approx 2;  R.&droms: approx 2.5.   Toe claw 2, obviously.
Also R's tail chevrons are intermediate in length between Ax and droms.)

Looking at the narrowest point in the metatarsus...
Ax:  a little nearer the top;
Droms:  pretty well the middle;
Arctos:  The "main waist" is near the middle but there is a kink in MT2
near the bottom;
Rahonavis:  Nearer the bottom, as in uncinated (ie non-enant.) birds.

In this characteristic, R. is nearer to droms than Ax (though not
intermediate), and it puts R nearer to modern birds than Ax.

> Now there
> are one or two features that are more like advanced birds in
> dromaeosaurids than in _Archaeopteryx_ (full opisthopuby,
> for one), but most of the weight of the data puts Archie
> closer to modern birds.

But that includes characteristics bound together with each other and with
flight-relatedness.  They are being wrongly treated as independent.


>In fact, under Greg Paul's hypothesis in PDW, neither Archie
> nor dromaeosaurids were closer to later
>birds than the other one:

But that wasn't what Larry said.  His original point was that
"...Dromaeosaurs seem in many ways MORE advanced than Archeopteryx, and for
that matter, so is Rahonavis."

The first Troodon was more closely related to Ax than to the last Troodon,
but that's not the point;

PDW,P152: [the first "public" floating of the idea]:
"Feathered flying Archaeopteryx is the first bird... .  The theropod
Velociraptor is nearly identical to the first bird and may be its
descendant"

etc etc etc.


> his hypothesis was (Archie + dromaeosaurids) +
>(various maniraptorans in series + later birds).

It wasn't.  Archie is predominantly put forward as an ancestor of the
groups: droms and later birds (exact relationship unspecified, though droms
would've had to have been descended from an intermediate more
flight-advanced than Ax).  (I know you don't like ancestors, but this is one
case where it may well be applicable).  Greg wasn't sure exactly where the
various other maniraptorans and arctos went, and was careful not to go
overboard on it.