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Marine reptiles



I'm not certain how ichthyosaurs made it to the dinosaur discussion 
forum, but then I could say the same for many other off-the-subject
items that appear here with some frequency.  Some time ago Paul Willis
wrote about an Australian opalised ichthyosaur for sale at the rather
steep price of $60,000 AUS.  I could care less about the opal, but I am 
interested in the ichthyosaur (not to purchase, mind you!).  Has it,
or will it, be examined, identified, and described by a professional 
ichthyosaurologist?  Is there any possibility that it is something other
than _Platyterygius_, assuming that it may be of Cretaceous age?  Is it
older?  In other words, does anyone know the status of this specimen?
With luck, Mary Wade of the Queensland Museum will have had a chance to
look it over.  I would hate to think the specimen could wind up in private 
ownership rather than be acquired by a museum or university.

Another contributor to this list, whose name I have forgotten, flatly
stated that ictiosaurs (sic) belonged to the Lepidosauria.  No way Jose.
The differences between ichthyosaurs and mosasaurs, for example, are vast.
After years of studying ichthyosaurs, I think it safe to say they are
are neodiapsids.  From that point on it gets difficult.  In a number of
ways they seem closely allied to the Younginiformes (formerly included
within the Lepidosauromorpha), but have other characters which would
show a relationship with the Sauria, which includes the lepidosauromorph
and archosauromorph clades as defined by Gauthier, Kluge, and Rowe (1988)
and Laurin (1991).  Within the Sauria, they definitely show closer
relationships with the lepidosauromorphs (but _not_ lepidosaurs) as
opposed to the archosauromorphs.  For now, it seems they fall into a yet 
to be defined region between the Youngiformes and the Lepidosauromorpha
clade of the Sauria.  I'm working on it!  One of the biggest problems
when working with many marine reptiles is the limbs.  Classification of
terrestrial amniotes places heavy reliance on limb characters.  Any 
synapomorphies between the limbs of _fully_ marine reptiles, such as
ichthyosaurs, and terrestrial tetrapods are virtually impossible to
define.

I can't seem to get away from marine reptiles.  Books on Bill Hunt's wish
list included an illustrated encyclopedia of ancient marine reptiles.
I can go along with that.  The last publication devoted solely to such a
subject was Williston's, "Water Reptiles of the Past and Present," which
came out in 1914.  However, for junior paleontologists, a small, but
beautifully illustrated and informative book by Judy Massare was published
in 1991 by Franklin Watts, Inc., entitled "Prehistoric Marine Reptiles: Sea
Monsters during the Age of Dinosaurs."  Betsy Nicholls of the Tyrrell
Museum and I are coediting a book to be published by Academic Press in
the near future with the tentative title, "Sea Reptiles of the Past."  It
will not be encyclopedic however, but will reflect some of the research
currently underway on marine reptiles by a number of vertebrate
paleontologists.  Nuff said.  Comments would best be addressed to me,
thereby keeping this a dino forum.

Jack M. Callaway
Vertebrate Paleontologist
callaway@icsi.net
Laredo, Texas