Re: back to pteros

[David Peters <davidrpeters@earthlink.net>]

>
>
> <And with regards to pterosaurs, I bow to Luis Chiappe who says (and
> illustrates):
>
>  "This specimen is indistinguishable from both juvenile and mature specimens 
> of
> Pterodaustro ? with its long, slender snout and evidence of filament-like
> mandibular dentition.">
>
>   This is good for *Pterodaustro* and, as identified, shows exception to a
> rule. Show me prevalence of a "non-rule" in other vert groups aside from a
> pterosaur or two? Note that several exceptional animals with long snouts such
> as gharials and cranes have short snouts as juveniles. Chiappe's subjective
> decision in indistinguishability is, as has been stated before, largely
> unquantified. This doesn't invalidate "juvenile features" as has been noted
> before. Prove me wrong by invalidating the features I noted.

The first ptero egg turned out to be an anurognathid. You're not going to get
additional rostrum shortening in this clade, so it's rostrum is as short as 
those
of other anurognathids. The second Chinese ptero egg belongs to a basalmost
ornithocheirid still retaining some cycnorhamphid characters (long legs, for
instance).  You can see my take on it at:

www.pterosaurinfo.com/haopterid_egg.html

Note that the rostrum shows no shortening whatsoever.

Your examples of gharials and cranes unfortunately slipped back into archosaurs,
which are born cuter than most, as noted earlier.

Chiappe's decision might have been subjective ( personally, I think he measured
everything that could be measured), but I measured it and made side-by-side
comparisons ? and in this case, the good doctor's judgement was spot on.

>
>
>   Incidentally, the *Massospondylus* embryos look rather like lizards to me,
> with not exceptionally short but deep snouts, and actually remind me of "Baby
> Louie", proposed as a therizinosauroid. This is in contrast to the Auca 
> Mahuevo
> sauropod snouts or embryonic birds, but since the sauropod skulls show clear
> lachrymal and jugal anatomy of adults, there is differentiation from
> homogeneity among sauropodomorphan embryos. The more triangular skulls of
> theropod embryos and the curve-snouted croc embryos are in stark contrast in
> archosaurs.
>
>   Cheers,
>
> Jaime A. Headden
>

It would help, Jaime, if you indicated what sort of lizards  they rather look
like.

; - )

with regard to David Marjanovic's entreaties to find examples where the 
Photoshop
method works better than microscopic observations, I can think of only  a one
example where that has been tested by others

1. The original Langobardisaurus paper by Silvio Renesto described a complete
skeleton with a skull and cervical series preserved beneath the rib cage. The
reconstruction showed a rather low skull with Macrocnemus proportions. My 
tracing
of a photo indicated a large, short-snouted, giant orbit (rather juvenile in all
aspects!) skull that subsequently was validated by the third Langobardisaurus
specimen with a skull out in the open.

Other observations, such as the posterior of Longisquama, the forelimbs of
Sharovipteryx, the narrow chord wing on Sordes, the palate of Jeholopterus, the
sclerotic ring that turned out to be a premaxilla in Tischlinger's tiny
anurognathus and the like, have yet to be considered by others in print ? one 
way
or the other. Private requests to demonstrate alternate reconstructions and
phylogenies based on same have all gone unanswered ? but you can't blame them if
there's nothing there!

; - )

David Peters
St. Louis