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Re: Dinosaur Planet, parts 3 & 4



> the dangers of assumption (phyletic bracketing) is that it limits what
dinosaur "could", "had", or "did" by the animals we have today. I tend to
take phyletic bracketing with a grain of salt because I question whether a
secondarily aquatic reptile is truly representative of the "primitive"
archosaur.

Of course it isn't. But those features that crocs and birds still have in
common ought to be representative. For a bracket, at least two are needed.
:-)

> One must also becareful in the assumptions made about birds (i.e., picking
the stand-in). Witmer argued by phyletic bracketing that birds and crocs
lack muscular cheeks, therefore ornithischians lack them as well.

Well. Phyletic bracketing just says that if one claims that ornithischians
had any sort of cheeks, one has to carry the burden of evidence. In that
particular case, there is indeed evidence that ornithischians had cheeks;
therefore phyletic bracketing by itself won't lead to the most parsimonious
hypothesis..

> As for footprints, as I pointed out in Eggs, Nests and Baby Dinosaurs, the
hatchling hadrosaur tracks from Utah do NOT occur with adult tracks.

Are you sure that the following two points are incorrect:
- The hatchlings were so light that they wouldn't have made tracks on ground
that preserves adult tracks.
- The adults were so heavy that they wouldn't have set a foot on the soft
ground that preserves hatchling tracks. (Assuming that any are known. Which
I've forgotten.) This need not mean e. g. staying out of an entire swamp; it
can also mean taking a long step over a puddle through which the hatchlings
have to run.