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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

  Where the Wind Comes Sweeping Down the Pampas!!!!

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