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Re: Those supercrested nyctosaurs



Colin McHenry wrote:

> Conway, Cunningham, Gerritsen, and McHenry presented an aerodynamic model
> for Nyctosaurus, based upon KJ1  & 2, at CAVEPS last year.  The presence of
> a membrane was assumed, based upon the superficial similarity of the crest
> to the mast and boom of a sailboard, and following an earlier suggestion by
> Dino Frey.

Actually, in my mind we were careful not to assert a belief in the actual
presence of a membraned crest.  We were interested in what effects such a
membrane crest might have if it were actually present;  if it could be viable
and have some beneficial effects on bioenergetics.  Our initial work suggested
that under some circumstances it could indeed be beneficial so long as an
appropriate part of  the animal was in contact with the water most of the time.
However, in order not to present a biased perspective, one of the images that we
present with our talks on the KJ specimens is an alternative antlered version of
the beast.  Personally I do not think there is strong evidence for or against a
membrane crested Nyctosaurus.  But the benefits are substantial enough that
further work is warranted on the concept, both on the benefits and on the
problems presented by a membrane crest.

>  Preliminary calculations suggested that the hypothetical
> membrane could have acted like a sail during low level flight, as long as
> there was contact between the animal and the water surface sufficient to
> resist the leeway (sideways horizontal force) caused by the action of the
> wind upon the 'sail'.  Such contact could have come from the mandibe during
> skim feeding, or from e.g. the wing.  At windspeeds between 6 and 9 knots
> our model is calculated to make reasonable progress over the water.  Climate
> simulations of the WIB during the middle Cretaceous suggest that these
> speeds would have been within the normal range of expected windspeeds.
>
> Of course, whether or not our model has any relevance to what Nyctosaurus
> was actually doing is unknown.  One problem facing any future work on this
> topic is that the specimens are not in a public collection.