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RE: Hanson 2006, Mortimer, Baeker response

Christopher Taylor wrote:

    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.

I think context is crucial here. We only have Euornithopoda because we had Ornithopoda before it. Euornithopoda was conceived as a subset of Ornithopoda. This is also true for Neosauropoda and Eusauropoda within Sauropoda, Eusaurischia within Saurischia, Neoceratopsia within Ceratopsia, and Euarchonta within Archonta. And so on. I support PhyloCode's notion that it is inappopriate to have taxa like Euarchonta enduring if and when Archonta is defunct.

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.

Yep. Also, in genus nomenclature the prefix 'Eu' is often tacked on when the original genus is found (or thought) to be preoccupied - such as _Eucentrosaurus_, _Euhelopus_, or _Euowenia_. But as you say, the context is different. When ruling whether Eu- is an appropriate prefix, Euornithopoda or Euarchonta represents a totally different situation to _Eugagrella_ or _Euhelopus_ etc.

In these
cases, 'eu-' might be interpreted as meaning 'what everyone _originally_
thought of as [taxon]'

_Eucoelophysis_ is such an example: the name implied that the material was conspecific with the *original* _Coelophysis_ type material. However, as it turns out, this may not be the case.