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RE: crocodile reversed or normal




-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of Ken
Kinman
Sent: Tuesday, August 22, 2000 12:21 PM
To: dinosaur@usc.edu
Subject: Re: crocodile reversed or normal


I'll take a stab at this:
      I think you may be confusing Family Ornithosuchidae with the clade
Ornithosuchia.  Due to some quirky cladistic anchoring, Ornithosuchidae is
now included in Pseudosuchia (not in sister clade Ornithosuchia).  For this
reason I prefer using the term Ornithodira (which I believe still contains
the same groups as Ornithosuchia).
     Anyway, dinosaurs have croc-reversed ankles (as do all other
Ornithodira).  I believe that some of the primitive pseudosuchians (sensu
Gauthier) also have croc-reversed ankles (e.g., Erpetosuchidae), and you
dinosaurologists correct me if I am wrong, but I believe Family
Ornithosuchidae may also have croc-reversed ankles.  If this is true (will
have to recheck on this), I'm not sure why Ornithosuchidae is included in
Crurotarsi, but could be another one of those cladistic nomenclatural
quirks.
     It is all rather confusing, but the croc-normal ankles ("cross ankles")
apparently only occur in crocodylomorphs and other "advanced" Pseudosuchians
(but not the most primitive ones).  And to clarify, I am talking about
Pseudosuchia sensu Gauthier (not Pseudosuchia sensu Benton, which most
people call Suchia).
     Boy, I sure would hate to have to explain all this to a class of
college undergraduates.  I can see them all rolling their eyes in disbelief,
and I wouldn't blame them one bit. :-)
                            -----Ken Kinman

Thanks. What I need to do is figure out where to put Ornithosuchus,
Riojasuchus, etc.
Tracy