Re: AN OPEN PLEA

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

Peter Buchholz  Tetanurae@aol.com said on 21st Jan 99:

>To Mr. Jackson and others,
>Please please

[snip]...

...>PLEASE take a look at any sort of elementary text
>that has to do with historical geology.  I beg of you to take a look at the
>sea level during the Middle Jurassic.  Hey, do you notice that it's very
high?
>Also, perhaps you can open up Predatory Dinosaurs of the World and take a
look
>at the phylogram.  How many named theropods are known from the Middle
>Jurassic?  ONE.

On 5th Apr 98 I said this :

>By the way, presumably it is no longer true, as it was in 1988, that the
>"Gasosaurus Gap" as I think of it, is still 10 million years long?  (Total
>absence of any theropod fossil worldwide).  If it is, then what we're
looking
>for may really be there but hiding.

...and immediately afterwards, in a post entitled "Gasosaurus Gap" I said...

>Sorry, realised just after sending the email - the supposed "gap" is from:
>
> the last _Coelophysis_ and _Dilophosaurus_ about 197 mya,
>         mid Pliensbachian, early Jurassic,
>to
>  _Gasosaurus_, closely followed by _Proceratosaurus_ and the first
>   _Megalosaurus_ about 173 mya, Bathonian, mid Jurassic.

So yes, I was aware of it.  It's worth remembering the gap ends about 23mys
before Archaeopteryx, and between the end of the gap and the end of the J
there are quite a few smallish types known.


>Mr Jackson, I really can't grasp your reasoning in light of these facts...
>You claim that Archaeopteryx HAD to be ancestoral to things like
[snip]...

This statement of my actual opinion is taken from the website (written
pre-Xmas):

>In this analysis we have considered three criteria:
>
>Proof of 2F's absolute truth:
>    Still some way from undeniable proof at 1% confidence level
>    and above, using this evidence alone. [That was stratigraphic evidence]
>
>Balance of probability:
>    Definitely on the side of 2F.
>
>Adequate evidence that 2F is a viable theory that ought to be included in
any
>consideration of this issue:
>    Definite. 100%.

I think you were misrepresenting me there Peter, don't you?.  I do think 2F
is right, but not just for the stratigraphic reasons.  And the 100% I quoted
was for a different issue, as I think I made clear.

...> saurornithoidids, dromaeosaurs and oviraptors because these creatures
aren't
>found in rocks that predate Archaeopteryx, but how can you know that they
>didn't live at that time when you have virtually NO terestrial deposition
>during that time anywhere on Earth?

No terrestrial deposition in a significant period (say 23mys) prior to _Ax_?
Are you sure this is what you want to say?  Bits of how many specimens of
Ornitholestes are known?


>Don't you get it?  The single named theropod known from the Middle
Jurassic,
>Proceratosaurus, is a coelurosaur.

Irrespective of how you define your groups it still isn't a K type, nor does
it embody particularly well, their special features.  Why should Troodon and
Velociraptor, which survived for all 80mys of the K (not to mention probably
Rahonavis too) be so rare pre _Ax_?

 >From about the same time there are
>theropod teeth that are almost certainly from a dromaeosaur.. or a
>deinonychosaur ss as you will.

Are those the ones that might be from a drom/Troodontid?  That's a pretty
big range of variability - quite apart from the fact that teeth are known
not to be particularly reliable.  Or don't you believe Chris?


>There are plenty of coelurosaurs from the Late
>Jurassic as well, Ornitholestes, Compsognathus, and Koparion which is a
>freaking saurornithoidid.  There is also word of some tyrannosaur material
>from the Morrison,...

Koparion... a single tooth, and anyway from just a little prior to _Ax_.
Actually I'm beginning to pay attention to GSP's PDW hint that certain
significant forms may have branched off *just prior* to _Ax_ -  the
troodonts might be a possibility to my eye.   Not by much, but maybe just
enough to take them into the Kimmeridgian.  But at least it made it to the
Dinosauricon, unlike the Morrison tyrannosaur.  It's odd that we don't hear
about this very often.  Is there substantial evidence for it?


> which points to an AT LEAST Middle Jurassic divergence
>WITHIN Arctometatarsalia, which means that Arctometatarsalia diverged from
>Maniraptora AT LEAST by that time.

Not in my philosophy, Tetanuraeo. :-)


>Know the facts darnit..
>don't just make it up as you go along, or plainly ignore them...

Unjustified misrepresentation.