[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: ARCHAEOPTERYX PNEUMATICS & TEETH, etc



> - well, the
> Guimarota _Archaeopteryx_ sp. teeth have microscopic serrations. I
> don't have Weigert (1995) or Zinke (1998) to hand but I do have the
> new Guimarota volume. Oliver Rauhut's chapter on the dinosaurs
> _mentions_ the serrations, but they are clearly figured in Wiechmann
> and Gloy's chapter on 'pterosaurs and urvogels'. The serrations are
> minute and only visible under SEM, but they are there (Wiechmann
> and Gloy 2000).

Oho! Dr. Feduccia?

> These chapters (which, like the whole book, are a must have) are...
>
> Rauhut, O. W. M. 2000. The dinosaur fauna from the Guimarota
> mine, pp. 75-82. In: Martin, T. and Krebs, B. (eds) _Guimarota - A
> Jurassic Ecosystem_. Verlag Dr. Friedrich Pfeil, Munchen. ISBN 3-
> 931516-80-6.
>
> Wiechmann, M. F. and Gloy, U. 2000. Pterosaurs and urvogels from
> the Guimarota mine. In: Martin, T. and Krebs, B. (eds), pp. 83-86.
>
> Like most good academic books these days, it is offensively expensive
> and unavailable to you unless you're on an obscene salary. Oliver's
> chapter includes discussion and figures of the Guimarota
> _Stokesosaurus_ ilium (to which the tyrannosauroid premax teeth
> described by Zinke (1998) may be referable), possible
> _Ceratosaurus_, compsognathid, troodontid, dromaeosaurine and
> velociraptorine teeth. Most, but not all, of these taxa were reported by
> Zinke - the possible _Ceratosaurus_ record predates Mateus' report of
> this genus from Lourinha.

I've heard rumors of dromaeosaurine and velociraptorine teeth, but
troodontid ones... *Koparion* isn't alone, it seems.

> and a pneumatic fossa on the proximomedial
> surface of the pubis

On the pubis? Interesting... On the other hand, didn't someone mention that
the new carcharodontosaurid/-ine from Argentina has pneumatic furculae and
ilia? Seems like the extent of pneumaticity can't be used as a character in
cladistics any longer...

BTW, Chatterjee says that *Protoavis* has pneumatic scapulae... "Details on"
forthcoming.

> and, needless to say, also contradicts Ruben et al's
> (1997, 1999) contention that _Archaeopteryx_ had simple lungs and
> was apparently apneumatic. The discussion section of this paper is a
> refutation of the theropod physiology model invoked by Ruben et al.

Heh, heh, heh!!!

> Finally, we'll all heard an awful lot about David Marjanovic's article
> in _Quarterly Journal of the Dinosaur Society_ (which is now peer-
> reviewed), but there were other articles in there that may also be of
> interest to some...

I have got the volume in the meantime, and wanted to comment on these
articles, I just didn't have time... (exams continue, even though the whole
February is "holidays")

> Liston, J. 2000. _Archaeopteryx_ and evolution of feathered flight:
> the hidden story. _QJDS_  4 (1): 6-14.
>
> Massive historical review of everything about flight origins and
> discovery of key taxa, with (I think) discussion of Jeff's theory about
> crypsis and the evolution of feathers.

In his M. Sc. (what's this?) thesis, Jeff seems to have put up the idea that
it is no coincidence that (wing) feathers look so much like e. g. cycad
leaves and evolved for camouflage. He repeats this here.

> Naish, D. 2000. 130 years of tree-climbing dinosaurs:
> _Archaeopteryx_, 'arbrosaurs' and the evolution of avian flight.
> _QJDS_ 4 (1): 20-23.
>
> Unfortunately submitted before _Microraptor_ and recent SVP
> presentations by Alan Gishlick and Scott Hartmann, so it's pretty
> naive.

And the drawings that show Chatterjee & Palm's scansorial dromaeosaurs are
very beautiful, just Chatterjee always illustrates his "protodromaeosaurs"
with the head facing upwards and the tail used like the stiff feathers of
woodpeckers. I haven't read the papers by Palm, however.

> Tarsitano, S. F., Russell, A. P., Rodriguez, D. S. and Stegall, L. 2000.
> Aerodynamic evidence for the evolution of protofeathers and avian
> sister group relationships. _QJDS_ 4 (1): 24-25.
>
> Wing-tunnel studies show how protofeather models aid flow in the
> boundary layer in water tunnel tests. Need to reread it but they seem
> to argue that theropods could not evolve flight because the ventrally
> projecting pubis would generate too much turbulence. That proves it
> then.

"Abstract: The evolution of feathers is examined on the basis of their
aerodynamic properties as protofeathers. Testing of models [badly]
representing current theropod and thecodont [sic] body shapes reveals a
large turbulence/flow separation problem generated by the theropod
pelvic/hindlimb region. This renders them incompatible with the aerodynamic
requirements of flight."

Apparently regards two unspoken assumptions as proven:
1. Bird flight must have originated trees-down,
2. Feathers must have evolved for flight.

In their own words: "Thus, our results support the hypothesis that
protofeathers [enlarged scales, not dinofuzz] could have rapidly become
exapted as turbulence generators associated with enhancing the lift
generated by the body or limbs at higher angles of attack than could be
tolerated by smooth-surfaced skin architecture. These lines of argument are
associated with an arboreal origin of flight that includes a gliding phase.
The arboreal origin is at this time energetically more feasible than a
cursorial starting point as it employs gravity to create an airflow."
        Last sentences: "Whether such protofeathers would lead to increased
lift at higher angles of attack remains to be tested. If such tests
supported this view then there would have been selective advantage to having
protofeathers in an arboreal proavis."
        Does not mention one feathered non-avian dinosaur.

If one disagrees with these assumptions, the whole article suddenly says
nothing, except that theropods make poor candidates for a trees-down origin
of birds (heh, heh) and probably that Tarsitano et al. have poor knowledge
of relevant literature.

> Also an intelligent review of Feduccia (1996) by Richard Maddra.

Actually of the 2nd edition 1999 which isn't any better:
"The feathered dinosaurs are not feathered (*Sinosauropteryx*), or not
dinosaurs (*Caudipteryx*).
        Feduccia's arguments might have been convincing, but for the quality
of scholarship on display. Had I written an essay of this quality as an
undergraduate, I would have been slated for it -- and rightly so.
[...]
        Feduccia seems to proceed by omission and assertion. Having asserted
that the similarities of *Compsognathus* and *Archaeopteryx* are due to
convergence, he then goes on to argue that both *Sinosauropteryx* and
*Compsognathus* are both [his typo] aquatic lake dwellers, whilst
*Archaeopteryx* is arboreal. Need I say more?"

I really feel like retyping the whole page. And Maddra himself writes "I
could go on, but I won't".