re: snake origins, etc.

[david peters <davidrpeters@earthlink.net>]

 "Having limbs is
a real problem if you need to fit through small openings underground, as
anybody who has tried exploring in caves knows," Hedges says. "Your body
could fit through much smaller openings if you did not have the wide
shoulders and pelvis that support your limbs." 
-- Blair Hedges, a professor of biology at Penn State,

[A wee bit Lamarckian. ]

At 11:05 AM -0800 2/4/04, Morgan Churchill wrote:
>I read the article, then the abstract.  If snakes aren't related to 
>monitors, then what group did they find them closely related to?  I 
>saw no mention of any probable ancestor group, which makes me kind 
>of suspicious of this.

[Good catch. They not only have to squash the current theory, they have to 
provide a better one for good science.]


[And on the subject of pterosaurs, Chris, thanks the ref:

Codorniú, L. and Chiappe, L. M. (2004) Early juvenile pterosaurs
(Pterodactyloidea: Pterodaustro guinazui) from the Lower Cretaceous of
central Argentina. Can. J. Earth Sci./Rev. Can. Sci. Terre 41(1): 9-18

Their small size (~300 mm of
wingspan), the lack of fusion of several postcranial bones, the minimal
epiphyseal ossification, and the porous appearance of the periosteal
surfaces indicate the specimens died at a very early stage of postnatal
development. 

[Tiny adult pterosaurs also have these characters via paedomorphosis.]

The presence of derived characters unique, within
Pterodactyloidea, to P. guinazui (e.g., caudal vertebrae exceeding 16
elements) supports the proposed specific identification of the specimens.

[This turns out to be quite common in micro-ctenochasmatids and others. I note 
that manual 4.1 extends when folded to the distal antebrachium in the proported 
juvenile, as it does in all other micro-ctenochasmatids. In the adult 
Pterodaustro 4.1 extends to the proximal antebrachim.]

The new material provides anatomical information previously unknown for P.
guinazui and sheds light on allometric transformations during the growth of
this pterosaur. Comparisons with more mature and much larger individuals
support two major allometric trends: (i) the negative allometric growth of
the proximal portion of the forelimb, and (ii) the positive allometric
growth of the metacarpal IV.

[These characters are different enough to suspect a novel species or genus. The 
humerus and metacarpal IV don't change much during maturation. Only the 
antebrachium and the tibia. In the case of the better specimen, the tibia is 
longer than the femur, which means it's an adult. And ossification only occurs 
after juvenile independence.]

David Peters