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Re: Defining Ornithischia (was Re:)



David Marjanovic writes:
 > > Mr. Peters is using a character-based definition for
 > > Paranornithischia.  For example, Mr. Peters regards
 > > the following characters as important in establishing
 > > a relationship between Lotosaurus, Silesaurus and
 > > Lesothosaurus:
 > >
 > > 1. Ventral maxilla is narrow.
 > > 2. The orbit marks the halfway point of the skull.
 > > 3. The quadrate rises vertically and is concave
 > > posteriorly.
 > 
 > That is not a definition. It is a diagnosis. A definition would
 > have to mention at least one organism.

A phylogenetic definition would have to mention at least one organism,
yes; but there are other kinds of definitions, and for most of the
last 249 years, "key character"-based definitions were almost
universally used.

Don't get me wrong, I think phylogenetic definitions are definitely
the way to go; but to say that any other definition is not a
definition is revisionism.

Anyway, there's nothing to stop me defining Interestingdinosauria as
all members of Dinosauria that massed more than 10,000 kg.

 _/|_    ___________________________________________________________________
/o ) \/  Mike Taylor    <mike@indexdata.com>    http://www.miketaylor.org.uk
)_v__/\  "In the late 40s, it was felt by some academics that Britain
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         Unbelievable but true.  Those early computer pioneers certainly
         were morons" -- Andrew Brand.