Re: Conway's Velociraptor (and pterosaurs)

["Jaime Headden" <ja_headden@qilong.8m.com>]

I wrote:

<<why was this lost in pterodactyloids if the foot/leg useage in the 
uropatagium was the same?>>

James R. Cunningham (jrccea@bellsouth.net) wrote (who is graciously replying to 
my extended and drawn out headaches ... thanks):

<To increase aspect ratio of the flight surface?  And was it lost in all 
pterodactyloids?>

  Let me clarify my statement, then: I refer not to the fifth toe itself, but 
the extent or definition of this toe; in
pterodactyloids, it is a reduced small nubbin, often a small lumpy triangular 
phalange, when preserved or present at all, though in
rhamphorhynchoids, it is a particular elongated, double-phalange digit, and is 
set further apart thanks to the lacertilian-like
fifth metatarsal, much more widely and distinctly than in pterodactyloids. This 
should confer a distinct mechanical complex than
does the digit of pterodactyloids, though this is, obviously, agreed upon by 
most parties concerned and I did not doubt this
condition. Restorations of this toe, however, as in both Luc Bailly's and John 
Conway's work appears to control this digit in the
same plane in rhamphorhynchoids as the trailing edge is in pterodactyloids, 
suggesting an issue of redundancy. However, this digit
was retained for the majority of the Triassic and all of the Jurassic, and in 
similarly-sized forms with and without the digit, as
in the upper Malm of Europe, there was apparent mechanical selection to favor 
its presence alongside forms without it, as in
*Rhamphorhynchus* and *Pterodactylus,* and further into the middle Cretaceous, 
with *Jeholopterus* and *Sinopterus.* Which was why I
was curious as to any functional favoring in the upper Malm to the loss of this 
digit, and presence of a clade of pterosaurs to lack
it, to the apparent absence of pterosaurs with the digit in about 50ma.

<So that the hindlimb could play a more active roll in providing yaw command 
authority as the length of the tail diminished?>

  Ah. As in the digit providing a form of "elevator"? This would make sense, to 
some degree, except how pterodactyloids, lacking a
long tail or the digit, managed good yaw control if the digit and tail of 
"rhamphorhynchoids" conferred better yaw control.

<The pads don't point down. In that position, they would point aft and very 
slightly down, with the spreading such that the 4th toe
would be displaced (flexed) further aft than the 1st toe.  The pad orientation 
would appear to be rotated about 70-80 degrees
aftward of the ventral.  Think beaver.  At a distance and at low resolution, 
the two positionings appear much the same.  I preferred
Aspidel's positioning because he curved the toes more aftward to reflect the 
untwisted tibia and ankle in a way that made it more
apparent.>

  Then this is why I am concerned, as the art illustrated suggests (perhaps due 
to the view) that the pes faced ventrally given the
angle of the drawing's view; from above or below, the pes is fully exposed on 
its broad plane, digits radiating in a fore-aft
direction with, as Jim notes, some apparent twist in John's work as well as 
Luc's. This was not apparent to me before, but this
"twist" in the ankle orientation does not appear to pull the pes above 30 
degrees of a horizontal body plane, which is why I
perceived it to be "flat." This also makes me curious as to the horizontal 
orientation of the fifth pedal digit in nearly all
illustrations offered, though to my knowledge the fifth metatarsal was largely 
linear with the other metatarsals and did not allow
the phalanx (or phalanges) to point caudally and thus provide a horizontal 
flight surface for the hindwing, given the orientations
of the pes as illustrated. Am I missing something here? Would the phalanges or 
the metatarsal be twisted so that the pes, if largely
oriented "pads-caudally," to create this surface? The elements largely orient 
in the direction of the pads in preserved specimens,
so that a spread pedal "fan" or foot as illsutrated would operate in a 
different, and perhaps occlusionary, plane than the hindwing,
if present.

  Though I've heard a webbed foot as proposed for the few pes known to be 
surrounded in skin thanks to excellent preservation in the
Solnhofen, Chaoyang/Liaoxi, and Fergana Basins, I would wonder if the foot did 
not operate pads down how they contrubuted to the
flight surface, whether the metatarsals' preserved "spread" was not actual but 
preservational, and that the webfoot was rather the
dessicated skin of a normal, non-membraneous foot. So what does having a broad, 
fanned, webbed foot that is oriented largely so that
the first toe was ventral, the fourth dorsal and slightly aft actually gives 
the leg when in flight? Mobility of the foot as in
gulls and boobies appears to operate largely in the same plane as the tail 
during slow speeds for landing postioning, and the very
long digits (longer than the tarsometatarsus) permit the plane to shift in roll 
directions [okie, so bad terminology, meaning around
the long axis of the fuselage, or or around a parallel to this long axis]. 
Pterosaurs do not seem to have a similar pes with long,
extremely mobile digits, so I am rather curious.

  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.

  "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)