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RE: Hanson 2006, Mortimer, Baeker response

Tim Williams wrote:

> I also think it's a great idea to have a clade beginning with Eu- or
Neo- to 
> be inside the corresponding more-inclusive clade, especially given the

> situation regarding certain dinosaur clades.  For example, Ornithopoda

> (node-based) is defined to include _Heterodontosaurus_ but to exclude 
> _Triceratops_.  Thus, if heterodontosaurids are closer to ceratopsians
> to euronithopods, then Ornithopoda is invalid, but Euornithopoda 
> (stem-based) would continue.  This is very silly.

    I would disagree strongly in the case of 'Eu-'. This prefix (meaning
'true', as most listmembers are probably aware) has been widely used in
multiple circumstances in nomenclature. The first circumstance, as in
Eusauropoda, could probably be interpreted as defining 'what everyone
thinks of as a [sauropod, in this examples], excluding weirdo basal
forms'. Euornithopoda (and Eutriconodonta) probably represent a slightly
different sense, where a larger taxon has turned out to be
para/polyphyletic, but a significant portion still forms a monophyletic
core. Both these senses are consistent with the suggested rule. A
further sense of 'eu-', however, which a quick scan through my records
shows is mostly used at a generic level at present (but genera will
become just another clade under PhyloCode ;-) ), actually implies
_exclusion_ from the taxon it is named after - as examples, I find
_Eugagrella_, _Euphalangium_, _Eugaleaspis_, _Eucyclops_, etc. These
names usually arose because the new taxon closely resembles the one it
was named after, or because the original taxon turned out to be
polyphyletic, with the type species in one of the smaller partitions
while the bulk of the species need to be placed in a new taxon. In these
cases, 'eu-' might be interpreted as meaning 'what everyone _originally_
thought of as [taxon]'


        Christopher Taylor

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