Re: EARLY EVOLUTION OF 'BIRDS'

["Allan Edels" <Edels@email.msn.com>]

    Sorry, John -  I don't buy it.  Your statistics are dealing with (or
more precisely NOT dealing with) a difficult-to-quantify factor, namely the
likelihood of fossilization of small, rare fossils in often barren exposures
of sediment.  Jurassic exposures are more scarce and less examined than
Cretaceous.  (I am NOT including the Morrison formation here - anyway, those
exposures are for a relatively limited timeframe, in comparison with the
rest of the Jurassic).  Certainly, the Jurassic has only recently been
examined for the smaller creatures (AND here I exclude Solnhofen -  so sue
me :) ).  We need to look at 180 -150 mya, and we need really, really good
fossils!  We need Solnhofen or Liaoning class preservation!

    The problem that you do deal with, i.e. the time problem, is a difficult
one.  You fault Cladistics because it doesn't deal with time relationships,
and I agree it is an annoying lack.  However, it is also a strength -
Cladistics shows us relationships between the various animals, and therefore
it can predict (when we apply time relations to it) where a common ancestor
to the charted creatures may be located.

    The fact that we find bunches of Maniraptorians in the Cretaceous, and
one earlier bird (at the end - almost - of the Jurassic) does not mean that
they did not share a common earlier ancestor, especially since we have not
examined the preceding
10 -30 mya before _Archaeopteryx_ in sufficient detail.  (I expect arguments
on this - tell me I'm wrong!).  We find birds in the Cretaceous - not a hell
of a lot, but quite a few - are these descendants of a known Maniraptor
merely because they occur after
it?  Or perhaps all modern birds are late Cretaceous Maniraptorian
descendants, since they occur after the K-T boundary (excluding the recently
mentioned parrot), and are different than _Archaeopteryx_ and other early
birds of the Mesozoic - i.e. the enantornithine birds?  These are patently
ridiculous statements, but, if one looks at _just_ the time relationships,
then these statements are likely outcomes.

    As I said the time problem is a difficult one, and I don't have a very
good answer for it, except to reiterate the need for more fossils in the
sweet spot (ie. 10-30 mya prior to _Archaeopteryx_).  You are essentially
supporting George O.'s BCF theory, which, as I've said before, is a nicely
constructed logical theory - missing only sufficient evidence to back it up
{By the way, the only fossil that I think comes close to beginning to build
evidence for BCF is _Caudipteryx_ - I think that it was secondarily
flightless}.  Even George has said that BCF versus BAMM (or BAMM) would most
likely be very subtle - even with the best fossils.

    A modest suggestion - perhaps difficult to enact, but I think it would
be interesting to do:  Can we find a way to add time relationships to
Cladistic analyses - essentially, weighing the results of a Cladistic
analysis with the time relationships of the samples?

    Everyone knows that you can do nearly anything you want with statistics,
depending on how you load them.  (I remember calculating the statistical
death of the universe - based on entropy - of course, I don't believe it
will hold true - but it does work).  As Mark Twain once said - "There are
Lies, Damned Lies, and Statistics".  Just be careful of how you put things
together - beautiful, elegant theories are not necessarily true.

        Allan Edels

-----Original Message-----
From: John V Jackson <jjackson@interalpha.co.uk>
To: Matthew Troutman <m_troutman@hotmail.com>
Cc: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Thursday, November 05, 1998 9:11 PM
Subject: Re: EARLY EVOLUTION OF 'BIRDS'


>--Original Message-- From: Matthew Troutman <m_troutman@hotmail.com>Date:
06
>November 1998 01:23
>
>
>
>> [Siriraks Arrathrakorn said...]
>>>>After I have read some papers. I see that many fossils have feather
>>>>and may be origin of bird.
>>
>>>[JJ said]This is what many people say.  But many people are often wrong!
>>
>>[MT said]I agree to an extent with this if I understand your standing
>correctly.
>>
>>>Yes - they come after the first bird.  Not just some of them but all of
>>>them.  This means probably the origin is the other way round - these
>>>feathered dinos are *descendants* of birds.
>>
>>This could just be an example of a preservation bias.  Anyway, you
>>cannot use the fact that the birdlike dinosaurs came after
>>_Archaeopteryx_ as proof that they are descendents of _A._.  More
>>evidence should be gathered.  Thus far, I think that the evidence shows
>>that these creatures are long-surviving relicts that were close to the
>>ancestry of birds.
>
>As absolutely no-one commented on my post of last month which dealt with
>this, I'm repeating it now.  One or two temporal anomolies can be expected;
>50 or 100 or 200 look like evidence: [For 'maniraptorans', read
>'Arctometatarsalia + Maniraptora', as used by TMKeesey in his web site]
>
>[[start of inclusion...
>Matt Troutman: 4/10/98:
>
>>Another weakness of your hypothesis is its interpretation of secondary
>flightlessness in maniraptoriforms. A far better interpretation is that
>they are avian ancestors not avian descendents.
><
>
>Just for a moment considering the chronological order of appearance in the
>fossil record (I?m referring to the non-pre-Archaeopteryx appearance of
>maniraptorans), how many paradoxical instances make a piece of evidence?
>
>Jurassic fossils are rarer than Cretaceous fossils; it is also
>hypothetically possible that if we assume maniraptorans gave rise to birds,
>it may have been early in maniraptoran existence (though the more this is
>true, the weaker the case ? see below).
>
>(By chance, only a small fraction of the evidence appears between
>Archaeopteryx and the end of the J (assuming the China stuff is K) so the
>principle needs only slight re-phrasing to refer to either ?Pre-Archae? or
>?Pre-K?).
>
>Say the ratio of maniraptorans living in the K to those living in the J was
>A:B;
>Say the ratio of the chances of an indiv living in the K ever being found
to
>that of one in the J is C:D;
>The ratio of the chances of a maniraptoran we have found coming from the K
>to from the J is (A/B)*(C/D).
>The probability of any maniraptoran we have found coming from the K is
1/(1
>+ 1/ ((A/B) * (C/D)) ).
>
>The chance of N maniraptoran fossils all appearing after Archaeopteryx is
>this expression raised to the power of N.
>
>It is interesting to plug various values into this:
>
>A/B=3.01; C/D=2; N=30;  gives a probability of 0.01  .   Very unlikely, and
>bad news for BADD.
>
>However, perhaps a more friendly set of inputs would be if K mani?s were
100
>times as numerous as J ones, and the the K was 5 times as fossiliferous as
>the J:
>
>A/B=100;  C/D=5;  N=30;  gives a probability of 0.941  . Fine for BADD ?
>sort of.  However this combination assumes maniraptorans hardly existed
>pre-Archaeopteryx!!  And maybe N should be much bigger than 30.
>
>Perhaps the hypothetical pre-Archae maniraptorans were difficult to find
>because they were very small, and/or lived in conditions unhelpful for
>fossilisation ? they were living in forest trees for example. . . !!!
>Whatever assumptions we make, a BCF-type explanation is the only answer,
>using these probability calculations.  Maniraptorans therefore did not give
>rise to birds since they all postdate the first bird ? unless they were
>effectively early birds already.
>
>To return to the original quote, a far better interpretation is that
>maniraptorans *are* avian descendents (though not necessarily pterosaur
>descendents).
>
>There have been claims of pre Archae. Jurassic maniraptorans, largely in
the
>form of teeth, often unusually small.  You may call them maniraptoran but
>they will probably be small aerial forms, or larger non-arborial
descendents
>of them.
>
>JJ
>...end of inclusion]]
>
>Plug in your choice of parameter for preservational bias.  There's a PhD in
>there somewhere, by the way!
>
>
>>You cannot look at _Archaeopteryx_ and get a perfect
>>dromaeosaur, _A._ is too birdlike and derived.
>
>Reversible derivations for flight.
>
>>
>>>This is not what I think because there were two very big explosions,
>>>both just after the first bird known:  other birds, and bird-like
>>>dinosaurs. I would expect this - feathers give an animal great
>>>advantages no other animal has, and drives evolution in new
>>>directions.
>>
>>Of course, you have to show that the birdlike dinosaurs evolved from the
>>first-known bird.
>
>We..ell, it cannot be proved positive until an unbroken pavement of
>undeniable links is discovered - but the same goes for either theory.  Of
>course, if one wanted to be sniffy one could say one didn't have to prove
>anything (again)  :-).
>
>
>>
>>>All birds are descended from a very close relative to >_Archaeopteryx_.
>>Many so-called "dinosaurs" are also.  The fact >that cladistics doesn't
>>agree with this will be evidence that cladistics >is bad (when proof
>>appears).
>>
>>Where is your proof other than the temporal 'problem' (?) ...
>
>That's a lot more proof than one usually gets.  Most scientists would say
>those statistics were pretty damn convincing.
>
>
>>...and the existence of feathers?  Here's what I see;
>>
>>_Archaeopteryx_ is extremely birdlike with the hooked ectopterygoid, no
>>serrations on teeth, etc, birdlike braincase, single sternum, etc.
>>etc...
>>
>>Advanced birdlike dinosaurs show few of these features.
>
>
>All reversible flight adaptations.  (We've been here before ... many, many
>times!)
>
>JJ
>
>