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Re: Chatterjee and Templin 2004, review, part I (long



> 1. In the abstract C&T describe pterosaurs as â?oknuckle-walkers with
laterally directed digitigrade manus,â?? which is an a hard concept to
imagine until you realize itâ?Ts just one knuckle thatâ?Ts being walked on,
No. 4, but itâ?Ts kept elevated by I-III, which are not flexed at the
knuckle, but hyper-extended, as in all tetrapods except apes and anteaters,
I think.

Impressions of mc IV are very rare in Crayssac. I think I haven't seen any.
Fingers I, II and III are usually quite well visible.

> 4. C&T report: In pterodactyloids â?oThe fifth toe becomes relatively
short due to the loss of digits.â?? They probably meant phalanges, but even
this is incorrect as the phalanx count remains the same, only shorter,
except in one derived clade.

Well, outside your tracings, the ungual disappears.

> Terrestrial Locomotion - Stance and Gait
> 6. C&T report that pterosaurs were both quadrupedal and bipedal. Finally!!

Do they write why? :-)

No bipedal pterosaur track in Crayssac so far. But all except at most one
track are pterodactyloid.

> Forelimb Joints
> 10. C&T report: â?oDuring normal walking, the elbow would be directed
backward...â?? yet figure 7 shows the elbow oriented ventrolaterally.

You mean the forearm points upward???

> 11. C&T report, quoting Lockley et al. (1995): The manus tracks are
oriented laterally indicating lateral torsion of the hand. I know itâ?Ts
hard to work with a complete pterosaur skeleton, but when you do you
discover that when the elbows are back, as they in cowboys preparing to draw
guns from holsters, the palms are medial. Drop the hands  to the substrate,
whether a tree trunk or a sandy beach and the fingers are laterally
oriented. No lateral torsion is necessary. Raise the elbows and youâ?Tre
flying. Itâ?Ts that simple.

Almost but not quite. In the tracks, the fingers, especially III, extend
caudally, not laterally... it seems the metacarpals and fingers I -- III
were twisted so that their palmar sides faced cranially, while IV was
twisted (as you have explained in your Historical Biology paper) in the
other direction.

> 16. C&T report: â?oThe two halves of the pelvis are fused along the
ischial symphysis in all pterosaurs...â?? which is incorrect for a majority
of them in which the pubis and ischium are widely separated by a recess that
extends nearly to the acetabulum.

They talk about the ischia being fused (or sutured, I think...) to each
other. You are talking about the ischia (not) being fused to the pubes,
right?

> the typical theropod femur (is there one?)

If you don't go into phylogenetically significant details (trochanters...),
and ignore the largely size-dependent curvature, then yes.

> The complete elimination of the last three tiny (in birds theyâ?Tre d even
larger) transverse processes

In birds they are also more. They extend into the pygostyle, it seems -- 
even in extant birds.

> The same thing happened in mammals. Sure they have a tail, but it
doesnâ?Tt â?~wag the dogâ?T as it does in lizards, crocs and dinos.

:-D Well said!!!

> Ankle Joint
> 22. C&T describe: â?othe loss of the calcaneal tuber.â?? Pterosaurs and
nonvolant protorosaurs never had one.

Funny -- everything closer to dinos than to crocs never had one either, so
even under their own phylogenetic hypothesis they are wrong.

> 23. C&T report: â?oThe â?~crocodile-reverseâ?T joint... supports its
inclusion in the ornithosuchian lineage.â??

In this case I have misinterpreted "their own phylogenetic hypothesis". Hm.
Forget the above. Perhaps, just perhaps, I should try to find the paper. :^)

> 24. C&T report: â?o[unlike theropods]...the inner four metatarsals of
pterosaurs are subequal in length...â?? Not true. In basal pterosaurs, the
digits increase in length laterally. In scaphognathids up to basal
ornithocheirids the digits increase in length medially. This misstatement
over-generalizes the wide variety in pterosaur pedes that is largely
unreported in the literature (but no for long!)
>
> And following that, C&T continue: â?o...and do not show any tridactyl
trend [compared to theropods].â?? This never stopped pigs, cattle and goats
from becoming digitigrade. Why did pterosaurs need just three toes?

Do they talk about being digitigrade? They just mention the absence of
convergence to dinosaurs, IMHO.

> 25. C&T support Clark et al., (1998) and their pronouncement that the pes
of Dimorphodon weintraubi was plantigrade. While this specimen demonstrated
that the metatarsophalangeal joint was stiff, which rocked an earlier Padian
hypothesis, sufficient extension of the interphalangeal joints permitted a
low digitigrade configuration, as demonstrated by Peters (2000), and as
demonstrated by digitigrade protorosaur tracks matched by Peters (2000) and
Avanzini,  & Renesto (2002).

The pterosaur footprints in Crayssac are all plantigrade so far.

> Later the figure continues: â?onote manus digits were directed
laterally...â?? Digit I in figure 9 is directed laterally, but digits II and
especially III are directed posteriorly.

Yep.

> That canâ?Tt happen in a standard lineage of quadrupedal tetrapods unless
something intervenes â?" like a strictly bipedal phase!

Sure it can, when the hands become too specialized. There's no evidence for
the slightest bipedal phase in anteater evolution... or chalicothere
evolution, for that matter!

> Quadrupedal Walking
> 28. C&T report: â?oThe limbs in pterosaurs were held in a
near-parasagittal position.â?? Again, look at extant lizards capable of
bipedal progression. These make good models. Also make sure the axis of the
femoral neck is aligned witht the axis of the actebulum. That gives your
pterosaur femur a  sprawl -- bit a good sprawl.

Still can't have been very much, as seen from tracks.

> 30. C&T report (based on a digitized walking model by Henderson and Unwin
(1999) that: â?oIn pterosaurs, the center of mass lay between the two
girdles when on the ground.â?? A correct configuration shows that the center
of mass stayed close to the center of balance, between the shoulder girdles,
a point directly above the pedes in a bipedal pose with all elements in
balance. From there a slight pitch forward got a walk started. Again, this
is clear in the animation referenced earlier.

And it also means that the hands did carry more weight than the feet.

> 31. C&T report: â?oIn bipedal running, bent knees would confer speed.â??
Not sure what is meant by this. Donâ?Tt all tetrapods have bent knees?

Permanently bent ones, like in theropods, and unlike in elephants, humans or
bears.

> Even geese without feet can walk well.

???

> 34. C&T report: â?oMoreover, during the transition from walking to
running, the stance changes from plantigrade to digitigrade mode, making
less contact with the surface...â?? Hey, theyâ?Tre trying to have it both
ways!! The footprints are never digitigrade, even during rapid locomotion.
Clark, et al. (1998) demonstrated it, right? Where does this digitigrade
stuff come from? Thereâ?Ts no evidence for it in pterosaurs, that is... in
the clades of wading pterosaurs that were plantigrade that left all the
tracks (...a little tongue-in-cheek, but not for lack of logic.)

No evidence for wading has been found in Crayssac. Pterosaur tracks that
were made in very liquid mud are rare, and none so far seem to have been
made underwater.