[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Defining Ornithischia (was Re:)

Or can a diagnosis include characters that are only present in some of
the members?

Philosophical arguments have been made about this point (before phylogenetic nomenclature came along, at least). One suggestion was to regard secondary absence as a special kind of presence, so that snakes can still be regarded as tetrapods...