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

RE: Thoughts on the new Czerkas book (long)

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Tracy L. Ford
>         a) Theropods (or "theropods" or whatever punctuation you
> put around
> them)
> are not prohibited from climbing by definition!!! That was a
> remarkably odd
> statement!<<
> Really? I find it right on the money. Other than myself, George, Greg,
> Sankar, what other paleontologist believe theropods could climb?

Well, both I and Phil Currie have publically stated in talks at conferences
that we accept climbing theropods.

>         c) The elongate and robust third metacarpal occurs in other
> specialized
> theropods (e.g., ornithomimids), which are not then eliminated from
> Theropoda.<<
> But NONE are as long as Scansoriopteryx. The others are very very
> close the
> digit II.

Actually, there are ornithomimid metacarpi with the same proportionate size
mcIII (specimens at the RTMP).  However, they naturally lack the immensely
long digit III (truly a specialization!!), and (like typical ornithomimids)
they have long metacarpal I.

[re: Cryptovolans plumage]
> Well, considering Norell only had a few hours to look at the specimen and
> Czerkas et al had weeks, I'd go with Czerkas et al. (not to mention I've
> seen the specimen myself :) ). They had long, typical flight
> feathers on the
> 'wings'.

Yes, it definitely has long feathers on the wings: agree with that 100%.
However, it clearly ALSO has long feathers on the leg (or, to rephrase it,
the photographic evidence that they present is entirely consistent with the
long feathers posterior to the leg as being attached to the leg rather than
being displaced).

> >>  (I think that this is a case of the
> authors being 'the pot that called the kettle black'; they accuse
> Norell et
> al. of not seeing things that are their due to preconceptions, yet they
> themselves miss this anatomical detail (figured on Fig. 11) due to their
> own).  One can falsify me by demonstrating that these feathers extend
> anterior to the tibia and fibula.<<
> But, you can trace the feathers from the wing to the tibia, if you follow
> them. But figure 1 shows that you can see which 'wing' the feathers are
> coming from.

Given that a) the bases of the shaft of the feathers near the leg are all
spaced appropriately for being attached to the wing and b) that particular
batch of feathers are NOT aligned in such a way that you can take them and
move them to either of the arms (that is, if they were displaced they were
also reoriented to match the leg's bend rather than the bend in either of
the arms), it seems to me pretty convincing that Cryptovolans had both long
feathers on the arm AND long feathers on the wing.  Sure, not what anyone
necessarily wants, but that's what the anatomy says.

(An aside: it winds up being a dromaeosaur version of Heilman's
"Tetrapteryx" stage of bird orgins!).

>  >>(Among other things, would someone please demonstrate how an analysis
> (especially genus/species level one like the AMNH ones, Mickey's, Jaime's,
> or my forthcoming ones) PREVENTS the recovery of secondarily flightless
> dromaeosaurs?  Such a demonstration would not be "but that's not
> the answer
> you get", because not one us knows the True Answer (tm). The demonstration
> would have to be showing how the analysis could not, under any
> circumstance,
> yeild dromaeosaurs nested within known volant forms.)<<
> Show me the cladigram that does do that, shows how Dromaeosaurs are
> secondarily flightless. Since so many are fighting against it I'd like to
> see them show that they were secondarily flightless.

Ah, I guess you are missing my point.  We cannot test this by saying "they
never recover dromaeosaurids as secondarily flightless" because that might
NOT be the valid answer!  The test here is to demonstrate that a position of
dromaeosaurs within known fliers CANNOT be recoverABLE from the test, not
whether it was recoverED.

An analogy: Sereno's 1999 Tetanurae analysis in his Science paper was
*incapable* of testing the older model of alvarezsaurid relationships.  That
is, Perle et al. proposed that alvarezsaurids were nested within
Archaeopteryx plus later birds.  Sereno's analysis lumped all birds into a
single operational taxonomic unit.  Because a phylogenetic analysis cannot
place on single OTU *inside* another, Sereno's analysis was not a fair test
of Perle et al.'s hypothesis.  On the other hand, the recent AMNH analyses
are, because birds are represented by several separate OTUs; consequently, a
tree that has alvarezsaurs closer to (for example) Confuciusornis than to
Archaeopteryx is potentially recoverable.  It is not recoverED in their
tests, but it is recoverABLE.

> >>And the biggy: is this thing a flier? I have no problem per se
> with volant
> dromaeosaurs.<<
> Per se? In that statement you just said that you don't believe it. Your
> fighting against it, just like the majority of people. Get over it, they
> flew..

****Sigh...  I am NOT saying that they couldn't fly.  I am saying the
evidence is not there sufficiently to demonstrate it.

> >>However, how does one demonstate it?  You can't just pick up
> the specimen and toss it to see if it flies: if it does, then trilobites
> were also volant! ;-)<<
> Not trying to be sarcastic are you? :)

Sarcastic, yes, but demonstrating a point!  There are many behaviors for
which we would love to be able to unquestionably demonstrate for fossil
taxa, but if we are going to be scientists we can't act like 1970s media
hounds and simply declare these behaviors were there.  They have to be
subject to testing and falsification.

It is the fact that so many dinosaur paleontologists and dinosaur paleofans
do NOT act like scientists that we have such a lousy reputation among other
scientists (and guys, I know this is a shock to a lot of you, but it is

> >>Mere presence of feathers, even large ones on the
> arms, might be necessary but not sufficient.  My (admittedly quick)
> measurements of the best preserved feathers they show (i.e., ones
> where the
> shaft and the edges are both clearly present) finds an asymmetry
> of only 0.9
> at best: they assert these feathers are asymmetrical but do not show
> measurements to back up their case.  Fully powered flight would require
> sufficient mobility at the shoulders, in the arms, etc.: that MIGHT be
> possible, especially in basal deinonychosaurs.  Still, the case
> is far from
> established, and the use of conditional words like "may" or
> "possibly" would
> actually strenghthen their case.<<
> We only  know how MODERN birds fly. Which muscles, etc., we don't know how
> these kind of animals could fly. We HAVE to stop thinking of
> modern animals
> and look at how things could have been. This is a dogma of modern
> science...

Agreed: we have to look at how they could have been.  In particular, we have
to figure out ways of producing falsifiable tests to examine these

That's why I said that the addition of words like "may" or "possibly" (which
seem like they weaken an arguement) actually would have strengthened their
case.  That is, they set up the possibility based on this new evidence, and
open the field to further detailed research.

> >>A final note on peer-review: There is nothing in the above comments that
> couldn't have been corrected by serious peer review.  It's not a
> perfect way
> of doing things: errors (both technical and philosophical) can
> and do still
> make it through.  However, there is a better chance that some of these
> aspects *might* be caught and modified so that the paper as a whole stands
> better in the end.  Does that mean that you might not wind up
> saying exactly
> what you wanted to say to begin with?  Sure.  However, this MIGHT
> be because
> your reviewer caught some logical flaw in your arguement or some
> less-than-professional comment in your text: are these bad things?<<
> But the articles were per reviewed, look at the acknowledgements.

That is what bothers me: there are a lot of stuff (documented in my previous
comments and more) that SHOULD have been caught by the reviewers and/or
editors.  Yes, a lot of stuff slips by review in other journals, too, but
this batch had a really substantial number.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796