The Magical, Mystery Ptero

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

  Greg Paul has a new article out in _Prehistoric Times_, pre-emptorily writing 
on the *Nyctosaurus* skim-sailing
theory before publication of the data supporting that theory, which Jim 
Cunningham has been loathe to spill the
full beans on for a good reason.

  Paul, G. S. 2003. The magical, mystery pterosaur *Nyctosaurus gracilis*. 
_Prehistoric Times_ 62:46-47.

  Paul describes the possible life history of *Nyctosaurus,* using Bennett's 
recently described new specimens as
*N. gracilis,* though Bennett refrained from using a specific epithet in his 
own paper. Rather than forwarding the
theory of a sail-bearing crest, Paul describes the crest as 'a psychedelic 
structure that gives new meaning to the
neocreationist concept of "intelligent" design -- it looks like someone 
designed it while on LSD.' He also
describes the crest as 'like ... flattened deer antlers.' (Both quotes from pg. 
46.) It is a peculiar study on the
living function of a VERY peculiar, flattened, aerodynamically controlled 
crest. Paul makes an observation that is
worth some consideration: if the animal flew, the crest must have an 
aerodynamic component. The problem with this
is that even if the crest served a display structure, it will still be 
aerodynamic in form, or the animal was
landbound, so evidence against an aerodynamic function for a display function 
will be effectively nil, as any
aerodynamic structure will be exapted for in a flying animal, whatever the 
original function, and thus people would
be prone to see aerodynamic first, display second. Cranial crests likely served 
both functions, but the surface
area is widely variable. Anyway....

  Paul lists several reasons why the crest is more likely to be a display 
structure than an aerodynamic one:

  1. 'The combination of low surface area and failure to appear until all grown 
up suggest the crests were not
airfoils such as rudders, but were instead display structures.' (Pg. 47.)

  This has a lot to do with the idea that there are posteriorly crestless 
skulls of *Nyctosaurus,* which Bennett
states is unknown, so the idea that there are crestless skulls cannot be 
supported and thus cannot support point
one.\

  2. '[L]ack of anatomical evidence' (pg. 46) and (earlier, pg. 47) '[T]heir 
crisp edges differ from the amorphous
rims of the crests of pterosaurs in which keratin sheaths greatly expand the 
area of the crest.'

  I take this to mean the absence of any preservation of the "sail" as implied 
by Jim Cunningham and John Conway.
The problem with this is that while this my offer that the bony crest did not 
have bone fade into the keratin, as
occurs only in *Tapejara,* it would not prevent pterosaurs like 
*Germanodactylus* and *Austriadactylus* from
bearing what is generally agreed to have a bone-based keratin-sheathed cranial 
crest. This occurs in
*Gnathosaurus,* as well, where the bony margin is well-formed and not too 
irregular, but highly rugose and ridged.
The rugosity is not known in the beaks of pterosaurs (commonly held to bear 
keratin sheaths) or *Tapejara,* but is
known in *Tupuxuara* and *Thalassodromeus,* and more primitive, 
"rhamphorhynchoid" pterosaur crests. So the
conclusions of features of the bony crest as bearing keratin are not clear-cut, 
as birds and turtles both will show
"unfinished" and very porous bone beneath keratin beaks, and some show 
complete, smooth "finished" bone.

  3. '[S]ails only work when the mainbody of the vessel has a substrate that it 
can work against. Water in the case
of sail boats and ships, the ground or ice in case of sail????? [what are terms 
for sail driven ice runners and
land racers?].'

  To counter this, I will use the example of the extant skimmer, *Rhynchops,* 
in which this bird occassionally
holds the tips of its wings when flying levelly into the water to stabilize the 
water-penetrating beak. This has
also been used to support use of the beak in larger pterosaurs, in the writings 
of Jim Cunningham, and is likely
used by other "skimmers" like ornithocheirids.

  4. 'Also, when sailing against the wind the sail is set at an angle to the 
direction of travel, so a pterosaur
that tried to do this with its crest would also have to swivel its large beak 
to the side, creating a rudder effect
that would prevent the creature from moving in a straight line.' (Pg. 47.)

  This might be the point, but Paul does not argue the absence of a 
head-turning rudder effect in other crested
pterosaurs, from *Tropeognathus* to *Pteranodon,* *Austriadactylus* to 
*Tupuxuara* or the more impressively crested
*Thalassodromeus.* So these animals needed to fixed-headed in flight, or be 
incapable of head-turning during
feeding. The black skimmer likely does not turn its head in feeding, and the 
wing-tips in water insures stability.
As long as the pterosaur kept its head stable and in line, a "sail" would be 
little detriment. See point five for
more on the issue head use in water.

  5. Paul notes the length of the jaws in *Nyctosaurus* are even in length, in 
*Thalassodromeus* where the lower
jaw's tip is mediolaterally compressed with a dorsal keel, and an allusion to 
the skimmer, *Pteranodon* with a
longer upper jaw than lower with inferred surface water feeding as in dipping, 
separate from skimmers.

  Would like to note that ornithocheirids like *Anhanguera* show various 
modifications to skimming including a
lower jaw that could open to almost 90 degrees to the upper jaw, and a 
specialized upper/lower keel that stabilized
the jaw during the snatch-n-grab method of feeding. The offset of the upper 
keel suggests the attitude of the head
at max "snatch" position was pointing caudoventrally well into the water, and 
the wings would need to be in the
water to prevent the animal from being sideways or into the water head-long. 
*Pteranodon* shows the same
modifications of the jaw joint, suggesting great usage of the jaw at full gape 
with a bony "stop" to prevent the
jaw opening further, likely to brace it during maximum gape. Thus it would seem 
length of the lower jaw, and likely
shape of the jaw tip, would have little bearing on actual feeding habits as 
long as the wings weren't too deeply
water-lodged or the animal spilled to the side or forward and became 
destabilized. Jim Cunningham has also
described (and I think published) on the ability of dorsally flat-jawed 
*Quetzalcoatlus* to surface skim, so that
too reduces point five.

  Paul describes *Nyctosaurus* as having lived almost entirely on the water, 
coming to land only for breeding
purposes, as he proposes for other marine pterosaurs. This appears to be odd, 
because aside from the kingfisher
*Halcyon,* there are no marine birds which would dare nest on open sea, and the 
loons prefer near shore mats to lay
their eggs on. The sea otter also rears its young on protected mats of seaweed, 
but not open water, and there are
few exceptions to other large living animals that live entirely on open water. 
*Nyctosaurus* has fully capable
quadrupedal posture, even is walking was awkward, so I cannot see the 
possibilities of living on land being
difficult. Paul supports this by alluding to the walking posture of 
*Nyctosaurus* being difficult because of the
absence of manual digits, but that's odd because it can still (as used by 
Unwin) walk on the metacarpal-phalangeal
joint of the wing digit, as Paul illustrates in the paper.

  Paul notes that the crest of *Nyctosaurus,* which apparently appeared 
relatively late in ontogeny given the less
ossified surface of KJ2 versus KJ1, appears to show an "adult"-appearing full 
crest, implying that display is the
most likely conclusion for the "antlers," rather than a sail. But in fact, the 
conclusion away from a display via
keratin or skin-based crest coverage over the struts does not seem to hold 
positive evidence on Paul's side, so the
argument appears to favor only a display-related crest function, and this seems 
to be the sole support on the
matter. Paul also appears to contradict himself by saying 'It is less likely 
that the crestless specimens were the
girls and the crested ones the boys, although this cannot be ruled out until 
more specimens are sampled.' (pg. 46)
but then goes on to describe a scene which is also illustrated of an immature, 
*Pteranodon*-like stubby-crested
skulled female watching a full-crested, antlered male displaying, without any 
hesitation on remarking which are
male or female. As above and noted by Bennett, crestless specimens with a 
complete occiput are unknown, so this
conclusion as to the shape or presence of the crest in females is not tenable, 
especially given such absence of
crestless specimens of other species of crested pterosaurs. It seems 
unreasonable to assume we have recovered ONLY
males from the Santana and Crato Formations of crested species.

  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)