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

RE: Thoughts on the new Czerkas book (long)

-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
Thomas R. Holtz, Jr.
Sent: Tuesday, September 10, 2002 7:17 AM
To: dinosaur
Subject: Thoughts on the new Czerkas book (long)

>>I'll post my notes taxon by taxon, and limit it to the dinosaurs (however,
agree with Tracy: Pterorhynchus might be a reasonable sister taxon to
Sorry, it wasn't me, I just posted what Dave Peters said.

>>II) Scansoriopteryx (likely = Epidendronosaurus: they might be from the
time unit, as the stratigraphy of the newly discovered Daohugou locality is
questionable): okay, having seen this guy, I agree that the identification
of the various parts of Epidendronosaurus were correct.  Scansoriopteryx's
mandible is highly reminiscent of oviraptorosaurs in terms of the region
around the external mandibular fenestra; tail is more like eumaniraptorans
in details of the centra size and shapes.

        a) Theropods (or "theropods" or whatever punctuation you put around
are not prohibited from climbing by definition!!! That was a remarkably odd

Really? I find it right on the money. Other than myself, George, Greg,
Sankar, what other paleontologist believe theropods could climb? There's a
ton more palaeontologist don't believe they could climb.

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

>>Also, the authors once again conflate the "cursorial therory" of the
of bird flight with the "theropod position of birds"; as some of us have had
to say again and again and again, the two are NOT synonymous, and there
these authors even quote Chatterjee (who explicitly describes an arboreal
theropod origin) on numerous occasions.<<
I took it as they were more in agreement with Chatterjee than not.

>>Cryptovolans: The type specimen was previously described in Nature (Norell
et al. 2002 Nature 416: 36-37; see DML archives at
Should say, talked about, not described.
>>  Oddly, both slab and
counterslab are listed in Czerkas et al. as being at the Liaoning
Paleontological Museum  (LPM), but by Norell et al. at tehe Beipiao Museum
(BP); maybe two different names (and codes? annoying!!) for the same
insititution.  A second specimen is also described.<<
But the exact same specimen. Odd indeed.

>>Czerkas et al. correct some anatomical errors in Norell et al.'s
description: I agree with some of their corrections, but disagree with
others.  The new description clearly demonstrates a fused sternum in this
form (contra Norell et al.).  Czerkas et al. demonstrate the presence of
some long feathers on the forelimbs.  I disagree with their idea that the
long feathers near the legs are unquestionably NOT attached to the leg: the
base of all these long feathers, where preseverd, are fully consistent with
this critter having long leg 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
>>  (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.

>>Once again, typological thinking shows up in their description, but such
statements as "By definition, the fingers of all theropods have reduced
proximal phalanges and elongated penultimate phalanges" (p. 110) (in this
case, they show that ph. I of digit III is longer than any other non-ungual
phalanx in that digit, as in Sinornithosaurus).  Throughout they confuse (or
are at least do not clearly distinguish) 'sister taxon', 'ancestor', and
'precursor'.  They accuse cladists of requiring non-flying dromaeosaurs
(incidentally, don't recall anyone ever coding "Character XXX: 0,
non-volant; 1, volant" in a matrix!!).<<
Right, I think that was what they were getting at.
>>Consequently, they misunderstand
cladistic methodology, leading to statements like (pp. 119-120):
        "Not acknowledging that there is such a strong tendancy towards
flightlessness among birds has remained a major flaw in the current
methodology of cladistics which does not sufficiently account for such
reversals. Without such considerations of terrestrial forms possibily being
secondarily flightless, no method of phylogenetic analysis can present an
accurate interpretation of avian relationships. Not only has this failed to
have been properly employed, but by not doing so, cladistics has presented a
highly misleading interpretation of the evidence by arbitrarily insisting
that the ancestral origins of avian flight must have been from an
exclusively ground dwelling theropod dinosaurs. Since dromaeosaurs can no
longer be regarded as terrestrial precursors of birds, using them as the
evolutionary link between dinosaurs and birds in the manner that cladists
have proposed is shown to be invalid."
        Yikes!  Not quite as many errors per sentence as some papers on bird
origins I've read, but getting up there!<<
Ok, so who as done cladistically what they are saying hasn't been done?

 >>(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.

>>And the biggy: is this thing a flier? I have no problem per se with volant
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
>>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? :)
>>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...

>>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.

                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

Tracy L. Ford
P. O. Box 1171
Poway Ca  92074