Re: Conway's Nyctosaurus Restoration or Introducing the Bennett Prize!

["Chris Bennett" <cbennett@bridgeport.edu>]

I have a few observations regarding John Conway's painting and the
reconstruction of Nyctosaurus with a jib.

First off, I must say that I very much like the artistic aspects of Conway's
painting, nice composition and execution.  Howeever, I would like to take
issue with some of the scientific aspcets of the recosntruction.

I have been dismayed that so many have been so quick to recosntruct a
membrane between the two rami of the crest of Nyctosaurus.  I noted in the
paper that there was no evidence of a membrane between the rami, and that
includes no evidence in the structure of the rami themselves to suggest that
there was a membrane.  There are lots of examples of extant animals with
spikes and prongs whcih do not support a membrane, so why should there have
been a membrane in Nyctosaurus?  There are also no specimens of pterosaurs
that show any evidecne of a membrane supported by a crest--my interpretation
of the crest of the Tapejara specimen is one of incomplete ossificaiton of
the crest and prezservation of the soft tissue covering of a developing
crest, rather than one of a membrane supported by anterior and posteiror
parts of the crest.  I am waiting for someone to do a life recosntrcution of
a crested Nyctosaurus without a sail, and concerned that the sailed
reconstruction may become THE standard reconstruction.

Conway reconstructed the nyctosaurs skimming with their lower jaws in the
water.  I assume this is an adaptation of the Thalassodromeus interpretation
applied to Nyctosaurus.  Kellner and Campos interpreted Thalassodromeus as a
"skimmer" based on the "streamlined" cross-section of the distal mandible,
which has sharply pointed median dorsal and ventral margins.  They thought
that the shape of the jaw was suited to cutting through the water while
fishing in the manner of the extant Black Skimmer.  I and some other
pterosaur workers have some real problems with the skimmer interpretation of
Thalassodromeus--I think the mandible is not nearly as laterally compressed
as it should have been if it were to be a skimmer, I fear cavitation, I see
the ocean as nothing like the glass smooth ponds and lagoons where skimmers
fish, etc.  However, ignoring all those problems the mandible of Nyctosaurus
is not laterally compressed at all, and it has nothing like any of hte
speciallizations seen in Black Skimmers.   We might as well start painting
Great Blue Herons as skimming low over lakes and rivers, waiting for their
mandible to touch the wary yet unsuspecting fish, and then with a snap they
pluck it wriggling from the water and greedily slide it down their gullet.

Turning to the question of sailing nyctosaurs, although I have the utmost
respect of Jim Cunningham's command of aerodynamics I distrust a lot of
mathematical modelling because such modelling is only as good as the
assumptions upon which it is based.  Jim says that the calculations say that
nyctosaurs could sail with a cranial jib like that painted by Conway and I
have no hope of challenging his math because I managed to slip though high
school and college without taking calculus.  I have little to mount a
challenge other than my gut feeling that it would not work in the real
world; however, I do have two problems with the model that as far as I know
Jim has not explained away.  Sailboats, sailboards, land yachts, and ice
boats all rely on sails to drive their forward motion in much the same way
that Jim calculates that Nyctosaurus could have used its cranial jib to
drive its forward motion, however, Nyctosaurus differs from sailboats,
sailboards, land yachts, and ice boats in two importnat ways.  All of them
are in contact with a dense substrate that prevents them from moving
sideways in responce to aerodynamic force on their sail.  Nyctosaurus would
have nothing to keep it from blowing sideways.  The second way that
sailboats, sailboards, land yachts, and ice boats differ from Nyctosaurus is
that they all can rely on the distrubution of weight to keep them more or
less upright. Sailboats have ballast or a weighted keel that acts to oppose
the aerodynamic force on the sail.  Sailboards, land yachts, ice boats and
some sailboats rely of people hanging off hte upwind side to keep them  from
tipping over.  Nyctosaurus could do no such thing.  What could it possibly
do to counter the roll effect of a jib almost the same size as one wing?  It
could not shift its center of gravity, and it could not hang off one side.
Perhaps Jim assumes that Nyctosaurus would unload the upwind wing, but it
just doesn't seem likely to me.

Jim may wish to counter my problems with more calculations, but I propose a
better solution.  I hereby announce the Bennett Prize in the spirit of the
Kramer Prize that was to be awarded to the first person to fly a man-powered
airplane around a closed circuit figure-8 course.  Kramer offered something
like 5000 English Pounds and then increased it when no one won in a few
years.  I will award the princely sum of $25.00 or 25 Euros (whichever is
greater!) to the first person to build and successfully fly a model that
uses a vertical sail entirely above the center of gravity to extract energy
to drive its forward flight.

Lastly, I was amused that David Peters again brought up the discolored area
in front of the skull of KJ1.  I thought I disposed of that matter in my
June 15 reply to two inquiries by Peters.  Perhaps Peters will believe
Conway when HE says the slab is painted and the discolored area is nothing.

Chris


S. Christopher Bennett, Ph.D.
Assistant Professor of Basic Sciences
College of Chiropractic
University of Bridgeport
Bridgeport, CT  06601