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RE: Stegosaur volume of Swiss Journal of Geosciences
Michael Mortimer <firstname.lastname@example.org> wrote:
> Long postorbital horns are only known in ceratopsids and
> their close sister taxa (Zuniceratops, Turanoceratops,
True enough. But which one is _Ceratops_: "ceratopsid" or "close sister taxon"?
> I was countering your statement that Ceratopsidae should
> have never been named by Marsh because Ceratops was so
I didn't have Ceratopsidae in mind when I made that comment. After all, this
was the 19th century, so I think we can give Marsh the benefit of the doubt. I
was alluding to families named in more recent times that began as monotypic
families - like Mussauridae or Agustiniidae or Aberratiodontidae. The fact
that these families were named makes them 'available' - which I don't always
think is a good thing. It's like you're rewarding workers who erect new
families willy-nilly. Other workers are more restrained, and don't
automatically erect new families whenever they discover a particularly
distinctive new taxon. _Eoraptor_ and _Eocursor_ and _Mononykus_ could have
been granted their own families (because they clearly didn't belong to existing
ones), but weren't.
> Instead of ditching Ceratopsidae, why don't we define it in
> a way that will include Ceratops? "Ceratops montanus <-
> Protoceratops andrewsi, Leptoceratops gracilis" or
Yes, I'm fine with that. However, that means you have to go through the
motions of including _Ceratops montanus_ in a phylogenetic analysis. This
seems like a pointless exercise - all this extra effort just to have _Ceratops_
remain as the name-giving taxon.
> Allosaurus fragilis is probably indeterminate within
> Allosauridae based on its holotype. Neovenator should be a
> carcharodontosaurid under that family's definition, and
> Neovenatoridae was based on the results of a single
> dataset. Coelophysidae was also based on probably
> indeterminate material that had to be exchanged for a
> neotype. Iguanodon and now it seems Stegosaurus were based
> on material
> Iguanodon is probably not the same as the original Iguanodon
> (likely to be Kukufeldia). The "Brachiosaurus" that is
> well known is Giraffatitan. Pachycephalosaurus' type is
> just a skull roof that could prove indeterminate once we
> have more complete pachycephalosaurines. As far as I know,
> there hasn't been an in depth analysis of Diplodocus or
> Camarasaurus species in two decades, so who knows how longus
> (several caudals and chevrons) and supremus (8 vertebrae)
> will hold up. These kind of examples are why we need
> strict priority-based taxonomy which does not fall when its
> eponym is found to be an undiagnostic member, as opposed to
> some subjective, authority-based system where things get
> renamed or lose their type status whenever someone thinks
> they're undiagnostic.
No, I think for the sake of taxonomic stability that we need to maintain
well-known genera, even when they are found to have inadequate type species.
That's why I think it was a good idea to replace the type species of
_Iguanodon_, and to do the same for _Stegosaurus_.
You mention that _Allosaurus_ and _Coelophysis_ were based on indeterminate
holotypes. Well, a neotype was designated for _Coleophysis_; and a neotype has
been proposed for _Allosaurus_:
I know you know this; but I'm just mentioning these examples to show that
switching the type species and/or type specimen is an integral part of
taxonomy. It is not 'subversion'. Not all taxonomy is priority-based.
Sometimes entirely subjective decisions are made in order preserve taxonomic
Should _Diplodocus_ and _Camarasaurus_ be found to be established upon
indeterminate type species, then I'm sure a new type species will be proposed
for these two genera. This is preferable to either genus becoming a nomen
dubium, considering how entrenched they are in the literature.
> As the above examples show, what seems like a justifiably
> valid taxon now may not be judged that way in the future.
> valid in 2100 than Marsh's views are now. Sure Sinraptor
> dongi's holotype is rather complete, but there are questions
> as to its validity compared to the earlier named hepingensis
> and Yangchuanosaurus. Yangchuanosaurus was named over a
> decade before Sinraptor, and has a more complete sacrum and
> tail. Under your system, why not use "Yangchuanosauridae"
> as the proper name for the family? It's all subjective
> anyway, so you can't say I'm wrong that the 15 years of
> genus priority, possibility of Yangchuanosaurus being the
> correct genus name, and more complete sacrum and tail trump
> Sinraptoridae being named and defined first and being based
> on a specimen with preserved manus and pes.
All I'm saying is that Sinraptoridae is a better choice than
Metriacanthosauridae for this clade. I'm not saying that the best-known genus
should *always* be the name-giver. All I'm saying is that some families were
named after very poorly known genera, and I don't think priority-based taxonomy
is always helpful for family-level clades. And priority-based taxonomy is not
the gold standard anyway - otherwise we would use Dryptosauroidea (Marsh, 1890)
in place of Tyrannosauroidea (Osborn, 1906).