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Re: [dinosaur] Latenivenatrix, new troodontid from Dinosaur Park Formation, Alberta (validity of Troodon)



Thomas Richard Holtz <tholtz@umd.edu> wrote:

> A valid point. Which is why--like it or not--the ACTUAL practice in taxonomy
> is "common usage within the field", not the letter of the law.


Agreed.  There should be some discretion involved in choosing family
names, based on prevailing practice (and phylogenetic utility) -
rather than just the blind application of ICZN 'laws'.  After all,
families are now clades - something the ICZN could not have envisaged
when its stringent rules regarding 'family'-level names were crafted.
Nomenclatural priority shouldn't be the only reason for deciding what
a 'family'-level clade should be called.

Tyrannosauridae should certainly have preference over Deinodontidae.
I agree with Matt that the situation with Deinodontidae is almost
exactly the same as Troodontidae.  Thus, Saurornithoididae should have
preference over Troodontidae.  It's also worth remembering that the
current usage of Troodontidae only goes back to 1987.  Before that,
there were differing opinions over whether troodontids were theropods
or ornithopods.


(from a previous message):

> > "That's why ... Titanosauridae are here to stay."
>
> Actually, arguably not. Within Titanosauria there are several proposed and 
> employed "families" (Saltasauridae, Nemegtosauridae,
> Aeolosauridae, potentially others). It is not at all certain which of these 
> the Titanosaurus indicus material would belong to. If we agreed
> to put all of these in one family, that would be Titanosauridae. But if we 
> regard them as distinct taxa, and cannot affirm where
> Titanosaurus goes, we can continue to not use "Titanosauridae".


Excellent point.  An analogous situation could potentially arise with
_Ceratops_. We may not be able to 'prove' that _Ceratops_ actually
belongs in Ceratopsidae - after all, some non-ceratopsid
neoceratopsians have postorbital horn cores (_Turanoceratops,
_Zuniceratops_).  And _Ceratops_ is not defined (phylogenetically) to
belong in Ceratopsidae, because _Ceratops_ is not a specifier for
clade Ceratopsidae.  As it is, and assuming _Ceratops_ is a ceratopsid
(which I admit does seem likely for _Ceratops_, based on the
morphology of the horn cores), it is extremely difficult to determine
whether _Ceratops_ is a chasmosaurine or a centrosaurine.  The
_Ceratops_ horn cores bear a striking resemblance to those of certain
members of both groups.



David Marjanovic <david.marjanovic@gmx.at> wrote:

> OTU just means "line in a data matrix". Several specimen-level phylogenetic 
> analyses (of other clades) have been performed.

True - but these clades are taxa.  Once a species is declared to be a
nomen dubium, it is no longer a taxon.