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Re: Protoavis - etc



--Original Message-- From: Jaime A. Headden <qilongia@yahoo.com>: Monday,
March 01, 1999 06:10 AM



>Patrick Norton wrote:
>
><why would a theropod have such an advanced flight related structure>
>
>and Larry Febo wrote:
>
><<I believe there are Coelurosaurs outside of Avialae that possess an
>acrocoracoid tuberosity, so I'm not sure it is necessarily a flight
>related feature.>>
>
>  In the concepts of BCF and 2ndF'lessness, such a feature would be
>tell-tale signs of a common, early origin of flight. Or in BAMMness,
>it would be a sign of a development for something that was exapted
>into a flight structure. Doesn't mean "flight"; pterosaurs and bats
>lack such a feature and fly pretty darn well, as I'm sure Matt and
>other bird-types will say.


The acrocoracoid process redirects a muscle (did someone say the biceps)
from pulling the arm forward, and rotating the hand (if near the ground)
upwards, to pulling the arm in a more upward direction as well.  Useful for
flight of course, and as it goes crazy in advanced flying birds extreme
development can be used as evidence for that usage.  However other uses can
be made of it, as croc-types demonstrate, so in rudimentary form it's not
unequivocally flight oriented.  (Maybe useful for climbing amongst other
things.)

Much the same could be said for semilunate carpals.

---#---

Yesterday I made up for missing the Ostrom do by attending the one at Conway
Hall (interestingly a celebrated centre for free speech).  Mike Halgate
stressed that the three conditions claimed to unite Px & Cx with dinos (two
to do with the quadratro-jugal and one to do with the ischium) weren't
satisfactorarily demonstrated in the Nature paper which claimed the "final
proof".  Mike and Luis got too cross for me to get much from them, and I
realised again that internet discussions are in many ways a considerable
improvement over early modes.

Nice to see Luis's pictures in real life; the one with the stampeding
therizo's is about 2 feet by 18 inches.  On innocently asking a question
about theriz's feet I managed to start a fine squabble between Luis and
Darren.

Darren's talk on marine tetrapods revealed that walruses suck molluscs open,
and also threw some light on a long standing puzzle for me as to why the
apparently primitive looking mososaurs flourished in the late Cretaceous, as
the ichthyosaurs died out.  Apparently the shallow weed-clogged lagoons
which became much more common at that time, suited the undulating and
somewhat amphibious mososaurs better.

Darren said somewhat disconcertingly that the fibula of Caudipteryx reaches
the ankle whereas that of Archae doesn't.  However PDW seems to depict this
condition fairly similarly between Archae, droms and ovi's.

I've come to the conclusion that the similarity between ovi's and therizo's
is largely parallel.  As to the illium, this is due to the reduction of the
tail - in ovis through flight, and in therizo's through the adoption of a
vertical posture.

You may say pah, but I say that Lufeng 'therizo' jaw doesn't bear much
resemblence to Caudipteryx or to Oviraptor, and I think integument
considerations will bear this out.

---#---



--Original Message-- From: T. Mike Keesey <tkeese1@gl.umbc.edu>Date:
Saturday, February 27, 1999 12:01 AM
Subject: Re: WHAT CAUDIPTERYX SAYS


>Another thing occurs to me. I don't recall anyone mentioning this before
>(sorry if they did) -- if _Caudipteryx_ is an oviraptorosaur, since it has
>wings, that might mean wings are a primitive trait for all maniraptors.
>The question then would be the function of the original maniraptoran wing
>-- for brooding or for flying/gliding. If the latter, there's some
>validation for DinoGeorge's view -- oviraptoroids, deinonychosaurs, and
>probably therizinosauroids would all be secondarily flightless.
>


This view of 2F is not said to require a departure from the orthodox
phylogeny.