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Segnosaur Eggs



Mickey Mortimer (Mickey_Mortimer11@email.msn.com) wrote:

<Pressures could include clutch size, nest temperature, nest
structure, etc..>

  I'll add a few here, to round this list a little: humidity,
predation, habit of parenting, _lack_ of a nest,
parasite-brooding.... Clutch size would only affect size of the
egg, as I understand the issue.

<I could think of several reasons segnosaurs might have reversed
to a dinosauroid prismatic morphology- perhaps including a
difference in ovary morphology based on segnosaurs being
quadrupedal and/or herbivorous unlike other theropods, but like
other dinosaurs with dinosauroid eggshell.>

  I'd like to wonder at the reasons this specimen is being
called a segnosaur embryo. It does look segnosaurian, but I'd
like to see some synapomorphies from the abstract :) Anyway, not
to be crass, a few corrections:

  First: The ovary has absolutely nothing to do with the
formation of the eggshell. There are separate glands that
produce the shell just prior to extrusion. Second: Segnosaurs
are not in the least quadrupedal, not by any stretch of the
imagination. The wrist possesses a restrictive maniraptoran
morphology in possession of the form of a radius that was locked
with the ulna distally and a trochlear distal carpal 1+2, that
forced the wrist in a single plane. The elbow and shoulder are
maniraptoran in quality and do not allow the arm to act as a
quadruped's, irrelevant of how long it is. Third: Diet does not
affect eggshell morphology; this is largely an environmental
issue, such as the prescence of layers through evolution in the
progression from drenched to soggy/wet to moist to dry nesting
areas. Layers and pore structure and even surface structure does
depend on these factors.

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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