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RE: Thoughts on the new Czerkas book (long)



Tom Holtz wrote:

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

Tracy Ford (dino.hunter@cox.net) replied:
 
<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.>

  Tons. Many of them students. Currie, Xu, Zhang, Tom, Wang, Tim Williams,
Bakker, etc.... Theropods, by PT definition, are saurischian dinosaurs and
all dinosaurs closer to birds than to sauropods; no other definition,
other than a bipedal, predaceous dinosaur fits the idea of "theropod".
Nothing about this says anything about climbing. Czerkas is coming off of
a dogmatic approach that appears to boost his presumption that calling it
a climbing animal is "new" and "controversial." Norell and the AMNH team
have been talking about theropods in trees for years, as has Holtz. There
are no outsiders here, just different opinions.

<But NONE are as long as Scansoriopteryx. The others are very very close
the digit II.>

  *Daubentonia* is none the more remarkable for it's long third finger and
toe, except what it does with it. Which, rather contra to Zhang et al.,
has nothing to do with climbing. Other slender toed animals, other lemurs
and lorises, also use their slender fingers as does *Daubentonia*.
*Tarsius* is even more remarkable for adaptations to arboreal life in a
biomechanical design that is in some ways very "cursorial" and worth a
close look.

<I took it as they were more in agreement with Chatterjee than not.>

  Yet Czerkas indicates that dromaeosaurs are not theropods in his view.
This does not agree with Chatterjee, and requires evolutionary changes
Czerkas does not adopt. Chatterjee, for instance, sees and presents
dromaeosaurs as being well-nested maniraptoran theropods, not basal
dinosaurs. A view, I think, that continues to try to balance with a
particular Texan "proavian" that has been shown some considerable scrutiny
and criticism. Without ever explaining why, proponents of a early bird
divergence in the dinosaur tree (or outside it, as Czerkas has _also_
proposed, based on the recent basal position of pterosaurs and therefore
linking birds and pterosaurs now that Ornithodira includes crocs and such
-- shoving it all the way down to support the pterosaur--bird link instead
of proposing if it can happen in mammals and psittacosaurs, it can happen
more than twice, too) have stuck to this position despite the lack of
support.

<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'.>

  Actually, according to Mark, he had this particular specimen for quite a
while in his office alone. For some weeks, I was to imagine. Nothing
dismisses his time with it to validate Czerkas'. The latter does have a
cast in his own museum, though, and likely one of each specimen he has
described as well as the "Archaeoraptor" composite before it was broken
up.

<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.>

  I haven't seen this, so this is cautionarily drawn: how does one support
the continuation, rather than double-layering of integument, on both tibia
and arm? As I was to understand, the arm was examined for integument and
was found, but the rear structures to diverge from the hips instead. From
what I have seen, unlike the *Psittacosaurus* of Xu & Wang and Mayr et
al., integument does not progress _over_ the bone preserved in this
specimen. (For those that do not know, the "spiny" psittacosaur that Mayr
recently described has pebbly skin that progresses over the metatarsals as
well, giving them a continuous "speckly" or "spotty" appearance.

<Ok, so who as done cladistically what they are saying hasn't been done?>

  The logic holds that a sequence cannot be "known", only postulated.
Knowing who lost flight rather than seeing a flight-related condition or
just long feathery arms makes nothing towards a sequence, just are. One
then takes this in context to something else and proposes a sequence.
That's all. This is what Tom was talking about.

<Show me the cladigram that does do that, shows how Dromaeosaurs are
secondarily flightless.>

  Nothing can, just theory. Same as no cladogram can show dromies could
fly. They either could, or did not....

<Since so many are fighting against it I'd like to see them show that they
were secondarily flightless.>

  Please. Different opinions on origins does not mean fighting. Not even a
staunch position. It's those that curse and scream that the "other guys"
are idiots that fight, they refuse to listen or understand the
"opposition." Science is about ideas, not people.

<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..>

  They? There are more than just *Cryptovolans*? Because all the others I
know of (meaning, described) do not have the shoulders or arms (or
integument) to _fly_. This fellow's the only one _now_.

<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 la Dickson, rather? Helium inflation? Sauropods floated a la balloons?
Sorry, humor here. Because I have been analyzing flight mechanics and
evolution for a few years and the adaptations of arboreality, and those
that fly without special means (us), or beyond special limbs (insects) fly
by some very specialized and specific muscles. Those that had broad
sternae and flexed coracoids with raised glenoids have osteological
correllates that show _which_ muscles were used. There there is a degree
of unknowingness involved still shows that there can be differences, but
the bones show us that these would be very, very limited. Besides, what
does Czerkas think of troodontids? *Sinovenator*? Oviraptorosaurs and
segnosaurs? You keep getting birdy closer to these animals, until dromies
differ by just one or two features from their neighbors. *Ornitholestes*,
even? Czerkas has a bit to go to his theory, I think.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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