Ptero notes (long):

[David Peters <davidrpeters@earthlink.net>]

A few bulleted remarks on various ptero topics follows.

The Discovery article by Naish and Martill

1. Wing membrane extent -- ironically the Scaphognathus pictured at the
top of the article shows (or at least showed before it was prepared) a
narrow chord wing membrane with a short fuselage fillet between elbow
and femur. I am still waiting for _one example_ of a deep chord wing
membrane showing a forelimb-hindlimb linkage. And its not Sordes.

2. >> Notably, there is little indication that pterosaurs radiated as
small forms of terrestrial environments, as both birds and bats did.<<

This line from the text is confusing. Pterosaur tracks attest to the
fact that at least some pterosaurs walked and fed in terrestrial
environments (unlike bats, other than, perhaps the vampire). If instead
this refers to bird and bat origins (as dinosaurs and as [insectivores?
dermopterans? primates?] respectively) then from which non-terrestrial
diapsids did pterosaurs come? -- if both small pre-dinosaurs and small
prolacertiforms are respectively rejected and ignored?

3. >> Recent analyses of evidence for these claims, combined with
new data, better support claims for quadrupedality and exten-sive
wing membranes. Pterosaur hindlimbs are not suited for
bipedality or cursoriality; <<

In fact, in all aspects, they are better suited for bipedality and
cursoriality than the 19 living lizards that are currently capable of
bipedality and cursoriality. I'll keep harping on this until someone,
maybe from the next generation, listens.

>> new, articulated specimens and
abundant trackways reveal that pterosaurs were plantigrade
quadrupeds, <<

but these are all Late Jurassic and later waders, ignoring all the
anurognathids and basal pterosaurs with a different food gathering
techniques and foot design.

>>ill suited for fast running; and wing membranes,
preserved under exceptional conditions, reveal attachment of
the brachiopatagia to the shin or ankle. <<

Again -- A free steak dinner _for two_ to anyone who can show this on
even one pterosaur.

>> Plots of pterosaur hindlimb dimensions onto ternary diagrams reveal
that
pterosaurs were comparatively conservative in terms of
hindlimb diversity. Pterosaur hindlimb lengths also correlate
with forelimb lengths and, so far as we know, pterosaurs
never lost the ability to fly. These observations are in agree-ment
with evidence for quadrupedality and broad wing
membranes. <<

True in most cases but ~

Hind limb diversity: compare big-footed Pterodaustro to tiny-footed
Anhanguera.

Fore vs hind limb lengths: compare short-armed Austriadactylus with
hyper-armed Nyctosaurus.

Besides, the factors included in the ternary diagram have nothing to do
with bipedality. Anterior ilium length is the key in living lizards and
extinct diapsids of similar morphology.


>> New phylogenetic studies indicate that pterosaurs did not
descend from dinosaur-like cursorial bipeds, but from more
basal quadrupedal, climbing reptiles, though the exact ances-try
of pterosaurs still remains controversial.<<

I'm looking forward to this article. Are we talking about
prolacertiforms? Or are we talking about some hitheto undiscovered
quadrupedal climber? If the former, then small prolacertiforms were
dinosaur-like cursorial bipeds, though not related. If the latter, then
I guess all the prolacertiform synapomorphies (prepubis, big fifth toe,
attentuated tail, hypertrophied anterior process of ilium, etc,  etc. --
everything but the wing) are convergent.

>> Basal pterosaurs
exhibit: a dorsoventrally shallow body; <<

no more so than any other diapsid or later pterosaur

>> sharply curved hand
and foot claws; <<

MPUM 6009: manus claws curved, but not sharply curved, as in later
pteros; pedal claws no more than ordinary curve. Longisquama also has
curved hand claws.

>> feet in which the penultimate phalanges are
longest;<<

true, in the most basal pterosaur MPUM 6009, but not true in the second
to most basal pterosaur, Austriadactylus.

>> and sesamoids on the extensor surfaces of either the
hand or foot. These features, all indicative of tree climbing,<<

Yes!

>> Ctenochasmatoids include Pterodactylus and an array of
Late Jurassic and Cretaceous forms with needle-like meshes
of teeth, presumably employed in filter-feeding. Surprisingly,
recent studies indicate that Cearadactylus, a large predatory
ctenochasmatoid, named in 1985, is nested within this clade
of filter-feeders (Unwin, 2002). This implies both the evolution
of giant size within the clade and of a cranial morphology and
dentition equipped to deal with bigger prey than those
favoured by other ctenochasmatoids:<<

Even more surprising -- a newer unpublished cladogram puts Pterodactylus
closer to Scaphognathus than to Ctenochasma, which is closer to
Dorygnathus, via Parapsicephalus > Angustinaripterus > Gnathosaurus. And
Cearadactylus comes out as a much later descendant of Pterodactylus, as
the diagram correctly indicates.

>>something akin to a sea
eagle evolving from a spoonbill (Figure 2).<<

This should have been Dr. Unwin's clue that this could not be true.

>> While virtually nothing is known about
pterosaur reproduction<<

This will be known soon.

Re: Purbeckopus tracks.

Confession time: A few years ago, I trusted the outline of the pes in
Wright, et al. (1997) in reconstructing the phalangeal formula of the
trackmaker. Big mistake. Applying the new scanning technique I
discovered that I had reversed the digit order and that all of those
funny bulges around the digits were almost useless. With more details
now known, the track belongs to one of the short-metatarsal (=basal)
azhdarchids, not too far removed from Huanhepterus, as I'm sure Unwin's
talk with show.

Re: hind limb position in flying pteros.

On Oct. 7 I asked a few questions regarding John Conway's wonderful new
pterosaur illustrations.

1.  Considering the new wing model, what do you artists think of the
> terrestrial or arboreal situation regarding the hind limbs? Is it
> sprawling (knees out) or erect (knees essentially beneath the hip
> sockets)?

Jim Cunningham wrote >> Speaking as both an artist and as an engineer,
it would usually be
neither.  The knees are very slightly out when in the terrestrial
position, with the angle of the ankle placement on the tibia
compensating so that the articulation of the foot at the ankle is
vertical. But I've only tested that on one species. Certainly not what
one would think of as sprawling, but not quite vertical either.<<

It appears to me that the femoral head determines the typical angle of
the outgoing femur. In some species, widely sprawling, in others much
less so.

 2. Does the tarsus in flight have its dorsal side up?

Again Jim wrote >> No.  But the differential aftward flexing does make
the dorsal side visible from above. 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.  Also see
Jaime Headden's take: http://www.cmnh.org/dinoarch/2003Oct/msg00055.html

I understand what Jim is saying here. In pterosaurs with a spreading
metatarsus digit I is on top and digit IV is typically stacked below
proximally. Distally this could lead to a "card spread" except that
proximal articulations between the metatarsals appear to interlock and
prevent this from happening to the extent necessary for the appearance
detected in the illustration. Rather the metatarsus appears to be
variably spread in wading pterosaurs (and Anhanguera by descent),
apparently narrow for flight, and widespread for wading. As Jaime
correctly noted, the pads faced caudally in flight in all pterosaurs.
The metatarsus in Anhanguera, you'll note the foot and especially the
metatarsus is extremely reduced, no doubt because Anhanguera spent
little time on the ground, as in the modern albatross. Still trim tabs
don't have to be big.

In other pterosaurs with an appressed metatarsus no such card spread
would be possible, so only a toe spread  in the vertical plane (when
flying) is possible.

3. And if anterior, do the toes occasionally spread in flight as
spoilers?

Jim said >> Yes.  The aftward flexing of some of the toes to form an
airfoil would be a variable and transient feature<<

I was actually thinking about the effect a metatarsal spread in the
vertical plane, but flexing the toes backward is easily accomplished.

4. skipped

5. What is happening to the fuselage fillet seen on most pterosaurs? It
> seems to disappear or become unnecessary in the present model in which

> the knees are brought anteriorly close to the elbows?

Jim wrote: >>I don't think it is absolutely necessary, but it may still
be there and
likely is in a number of species.  It could help with flow control. <<

Perhaps upon landing? When the hind limbs might be extended differently?

6. What is the situation in basal pterosaurs regarding digit V? Is it
> actively involved with any flight membrane? Or is it tucked away for
> some other use?

Jim wrote: >> I think it may originally have been involved with the
uropatagium and then transferred more to the foot web in those later
pterosaurs in which
it may have been preserved. Note that I don't know which species those
may have been.  That implies that uropatagium loads that were originally

accepted by digit V were transferred to MT V in order to free the foot
from the uropatagium loading and to keep the uropatagium free of the
effects of moving the foot.  May well have had other, terrestrial uses
too.  I dunno about that.<<

In Sharovipteryx digit V is connected to the uropatagium, but digit V
extends anteriorly in this taxon. In pterosaurs, digit V is typically
found folded upon itself, completely tucked away, and typically angled
across the top of the metatarsus. In my opinion, digit V lost connection
to the uropatagium when this flexion occurred.

All for now,
See you in St. Paul.

David Peters
St. Louis