Re: Some Observations on Nyctosaurus

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

----- Original Message -----
From: "Jaime Headden" <ja_headden@qilong.8m.com>
To: <dinosaur@usc.edu>
Sent: Friday, October 17, 2003 8:34 PM
Subject: Some Observations on Nyctosaurus


> Thanks to Marco Auditore for sending me this paper, and permitting
> me to run over the discussions and data. I have a few
> observations to make on the nature of the skull and postcrania that
> Chris Bennett describes.
>
>   Bennett, S. C. 2003. New crested specimens of the Late Cretaceous
> pterosaur *Nyctosaurus*. _Paläontologische Zeitschrift_
> 77(1):61-75.
>
>   The first observation I have is on the taphonomy: in KJ1, nearly all the
> elements are aligned within 30 degrees of one another,
> suggesting deposition in a flow, rather than still, environment; elements
> not in this 30 degree range include the proximal ends of
> the first wing-digit phalanges, the disarticulated lower jaw, the left
wing
> metacarpal, and "ossified tendons" associated with the
> latter. The skull excluding the cranial crest is aligned cross-wise to
this
> degree, and is largely parallel to the lower jaw,
> suggesting that the crest may have had more of an effect in-stream
> during deposition than the bulk of the skull. In KJ2, the
> elements are aligned large in two directions, with the left side of the
slab
> aligned about 25 degrees from the slab midline to the
> left, and the right side aligned to the right about 30 degrees, though
this
> right side median is much more partial to cross-wise
> elements than is the left side, including the skull; the lower jaw is
aligned
> parallel to the right-side median, and the left side
> median lacks nearly any cross-wise elements except for portions of the
> broken crest. This is also suggestive of a flow-like
> deposition. Since I am unaware of the depositional direction of the slabs
> in situ, I cannot speculate otherwise, but the nature of
> the sediment, being chalk, indicates these were offshore, and not part of
> an inshore, stream or riverine environment, so the Great
> Interior Seaway most likely had a relatively strong sub-surface flow.
>

Please don't take this the wrong way, but ... so what?  I did not comment on
the possible alignments because I did not think them important.  It is not
news that there were occasional currents on the floor of the Western
Interior Seaway, but the specimens were on the order of 200 km from the near
shore and there is no evidence of transport.  Note that Nyctosaurus wing
elements were thin-walled, hollow tubes with a lot of surface area for their
mass and they are not transported away, simply possibly aligned.  It would
not take strong currents to simply turn a bone to align it with the flow.


>   My second observation is on the arm: based on the above alignment of
> elements, it is considerable to note that the  "ossified
> tendons" noted by Bennett are almost _always_ associated with wing
> elements. In KJ1, these are associated with the radius, ulna, and
> the wing metacarpals. Two are associated parallel and adjacent to the
> right MCIV, one is associated about 20 degrees and adjacent to
> the left MCIV, and one is associated parallel and adjacent to the ulna
> and radius, which were found as float near the rest of the
> specimen. In KJ2, the tendons are preserved parallel (< 20 degrees)
> and adjacent to the left MCIV, perpendicular to and almost
> abutting one end of the right radius and parallel to the posterior ramus
> of the crest, and as fragments both cross-wise and diagonal
> to the flow on the right side of the slab between the proximal and
> distal syncarpals, which are near to the right MCIV and first
> wing phalanx. This tells me that these elements are intimately associated
> with the wing.

Yes, the ossified tendons are associated with the wing musculature, and I
think I know which muscles.


>  Furthermore, the morphology of parallel
> fused fibers with striated but longitudinal structure, even though one
> end (proximal?) is bifurcated in KJ1 for two elements,
> suggests to me that these may very well pertain to very vestigial
> metacarpals I-III; their distal morphology is rounded and
> truncated, so it may be likely phalanges could have been present,
> but my gut at least informs me otherwise, and the phalanges may
> most likely be absent, and the fusion of the "tendons" as an effect
> of structural reinforcement of the elongated wing metacarpal.
>

You are mistaken.  As I wrote in the paper, one form of ossified tendon is
flat and has "a striated appearance indicating that it was made up of
multiple fibers before ossification", but the other is round in
cross-section, does not have a striated appearance, and bifurcates at one
end.  The second morphology  is tendon and clearly does not pertain to
metacarpals I-III, and note that I clearly stated that there is no evidence
of Mc I-III in either specimen.  I do not have time to discuss the evidence
here, and I suggest that you wait until I complete the thorough
redescription and revision of Nyctosaurus that is in progress.  Note that
the Pal. Zeit. paper was simply to document the crested specimens--they are
privately held and as you may know it is difficult to publish on privately
held specimens in U.S. journals.  Therefore, I simply wanted to get a
thorough description of those specimens published so that in my
redescription and revision I can refer to the information provided by them
by citing the Pal. Zeit. paper without having to describe the specimens.  As
a result, detailed discussion of the osteology of Nyctosaurus including the
questions of the ossified tendons and Mc I-III was put off for inclusion in
the redescription and revision.

Note also that ossification of the tendons in Nyctosaurus is most likely
related to the hyperelongation of the wing metacarpal and the need to limit
the elasticity of the consequently hyperelongated tendons.  Bone is less
elastic that dense fibrous connective tissue.


>   My third observation is not really an observation but a question:
> Bennett describes the other skulls of *Nyctosaurus* as
> crestless, but doesn't Williston's skull (I know not the number, and
> figured only to my knowledge in Wellnhofer's pterosaur
> encyclopedia and an illustration of the wall-mount of the type of
> *N. bonneri,* referred by Bennett (1991, 1994) to *N. gracilis* --
> the sole postcranial material of South American *N. lamegoi*
> is irrelevant to this observation) have a midline sagittal rostral
> crest, as in pterodactylids, germanodactylids, & dsungaripterids?
> This was not mentioned by Bennett. This skull is a tad different
> from those of KJ1 and KJ2, though it does not appear by much,
> so I am curious about the statement Bennett used on pg. 61: "1) they
> do not represent a new species[.]" What did *Nyctosaurus*' skull
> look like, then, if both are the same species, perhaps?
>

Do I really look dumb enough to publish a paper describing new crested
Nyctosaurus skulls and comparing them other Nyctosaurus skulls and not
include all available Nyctosaurus skulls?  Wait, don't answer that. Anyway,
I am not that dumb!  The specimen that you refer to is FHSM 2148, and I did
discuss it.  I also discussed the Field Museum specimen, FMNH P 25026, which
was described by Williston, and the Carnegie Museum specimen, CM 11422.
Before you get upset and ask about the Nebraska specimen, I will point out
that its skull exposed and eroded and all that was left was the anterior
part of the beak(s).  The structure on the premaxilla that apparently looks
like a crest to you is an artefact, the result of damage to the specimen and
inaccurate reconstruction by Sternberg--one can do all sorts of bizarre
things with plaster and brown paint, but that does not make them real. There
is no evidence in Nyctosaurus of a median crest on the premaxilla like that
of Germanodactylus, etc.  Note that I already commented on just this point,
which was brought up by David Peters some time ago.

Chris


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