Re: Ceratosauria vs. Neotheropoda?

[Mike Taylor <mike@indexdata.com>]

In short: taste, judgement and an understanding of the historical
background are required.  Any fool can define a clade, but doing it
well is not as easy as it looks.  Caveat author!

2009/11/22 Tim Williams <tijawi@yahoo.com>:
> Augusto Haro <augustoharo@gmail.com> wrote:
>
>> I suppose this later inclusion should not be considered as
>> the original meaning of the name. If not, Ceratosauria would
>> have to be phylogenetically defined as including both neoceratosaurs
>> and tetanurans to cope with the original meaning.
>
>
> I think you might be overstating the importance of "original meaning" in 
> framing definitions and converting time-honored groups to clades.  There's no 
> rule that says you *must* adhere to the original meaning of a name when 
> converting it into a clade name.
>
>
> For example, the name Ornithosuchia was originally erected by Huene to 
> include _Ornithosuchus_ (he erected Ornithosuchidae at the same time). 
>  However, since then Ornithosuchia has been used for a much larger archosaur 
> clade, and some definitions (e.g., "the most inclusive clade Aves but not 
> Crocodylia") would actually result in clade Ornithosuchia excluding 
> _Ornithosuchus_.
>
>
> Personally, I would prefer that Ornithosuchia be defined such that it 
> includes _Ornithosuchus_ - for the sole reason that the name was erected 
> specifically to include _Ornithosuchus_.
>
>
> Similarly, Pseudosuchia was erected specifically to *exclude* crocodiles 
> (hence the name).  Yet some definitions of Pseudosuchia allow the 
> crocodilian-containing clade Suchia to be a subset of Pseudosuchia, which 
> strikes me as ridiculous.
>
>
> In short, for clades such as Ceratosauria, Ornithosuchia and Pseudosuchia I 
> think the only nod we should make to "original meaning" is that the 
> definition reflects the intent behind the name.  Ceratosauria was clearly 
> intended to include _Ceratosaurus_; so even if ornithomimids had been 
> originally included in this group (they weren't), it shouldn't really matter 
> to the current definition.
>
>
> Cheers
>
> Tim
>
>
>
>