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Re: Nopcsaspondylus has no hypophene, please



I understand Sebastian's frustration at seeing these two
specimens/taxa confused, but I have to admit that I have made the same
mistake myself -- see the figure caption in this blog-post:
        
http://svpow.wordpress.com/2010/04/21/open-access-becoming-increasingly-inevitable/
and Phil Mannion's correction.

But I think it's a very bad idea to speak, even informally, about
"rebbachisauroids".  Every phylogenetic definition that's ever been
offered of Rebbachisauridae is branch-based, and so includes all the
candidate "rebbachisaur-like" taxa.  Salgado et al. (2004) is the
earliest such definition, citing a personal communication from Jeff
Wilson defining this clade as (Rebbachisaurus garasbae not
Diplodocus), and Taylor and Naish (2005) reaffirmed this definition.

If anything, it seems like Sebastian probably wants to coin a name for
a LESS inclusive clade with Rebbachisauridae.

-- Mike.




On 22 November 2011 19:41, Mike Taylor <mike@indexdata.com> wrote:
> On 22 November 2011 19:38, Sebastian Apesteguia
> <sebapesteguia@yahoo.com.ar> wrote:
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>
> Rescued from truncation, as this is a particularly important subject.
>
> -- Mike.
>
>
>
>
> Hi,
> in the last two years I've seen some papers with mistakes concerning
> the distinction between two specimens which I described in "The
> sauropod diversity of the La Amarga Formation (Barremian),
> Neuquén (Argentina)" (Gondwana Research, 2007).
>
> Specimens are:
> -MACN PV N35, a dorsal vertebra, which I described and figured, but not named.
>
> -Nopcsaspondylus alarconensis, another dorsal vertebra (which I didn't
> figured, only referred to the original paper by Nopcsa in 1902)
>
>
> Concerning MACN PV N35, I said:
> "MACN PV N35 is considered here a basal diplodocoid......"
>
> ".....it is possible that MACN PV N35 could belong to a form related
> to Zapalasaurus or that taxon itself. However, I prefer to maintain
> the distinction of MACN PV N35 from Zapalasaurus considering that..."
> "MACNPVN35 shares with rebbachisaurids........It must be noted,
> however, that the presence of a well-developed hyposphene shows a very
> basal position in the
> clade, like that of Histriasaurus boscariolli (Dalla Vecchia, 1998).
> Additionally, MACN PV N35 lacks all the following rebbachisaurid
> diagnostic dorsal neural arch features, the La Amarga taxon having a
> plesiomorphical condition for all of them: absence of
> hyposphene–hypantrum articular complex in dorsal vertebrae; posterior
> dorsal neural spine reaching four times the
> length of the centrum; and petal-shaped posterior dorsal and anterior
> caudal neural spines. All these features point to the need for
> creating a more inclusive category to include rebbachisaurids
> and the basal most forms related to them, as a lineage related to
> rebbachisaurids, but lacking several of their diagnostic nodebased
> features".
> and, finally:
>
> "However, although the material from Barda Alarcón and MACN PV N35
> indicate low spined rebbachisaurids (it should say rebbachisauroids),
> the latter specimen also retains a well-developed hyposphene".
>
>
> Concerning Nopcsaspondylus (a regular, Cenomanian rebbachisaurid), I
> offered the following diagnosis:
> "diplodocoid sauropod characterized by mid to posterior dorsal
> vertebrae with very reduced centra, forked medial
> centropostzygapophyseal lamina, lateral lamina of the neural spine
> formed by the spinodiapophyseal lamina plus a lateral
> spinopostzygapophyseal (different from that forming the postspinal
> lamina)."
>
> Well, in the paper of Demandasaurus, Torcida et al. say:
> "There are only two other rebbachisaurids in which the
> hyposphene-hypanthrum articulation is developed: Histriasaurus and
> Nopcsaspondylus (Apesteguía 2007)."
>
>
> Additionally, Whitlock say:
> "Apesteguía (2007) assigned MACN PV N35 to Nopcsaspondylus
> (??????????), which is contradicted by the presence of a hyposphene in
> MACN PV N35 and its absence in Nopcsaspondylus (Nopcsa, 1902)....For
> this reason, MACN PV N35 cannot be assigned to Nopcsaspondylus."
>
> Please, MACN PV N35 is an Early Cretaceous (Barremian) basal
> diplodocoid, perhaps a rebbachisauroid (in my concept, including
> Histriasaurus).
> Nopcsaspondylus is a Late Cretaceous (Cenomanian) regular
> rebbachisaurid, which I named in the paper only in order to
> differentiate from other specimens, thats why is not described, but
> added in an Appendix of Systematic definitions.
>
> I never mixed them or referred one to each other.
> Just that,
> Best regards,
> Sebastian
>
>
>
>
> Dr. Sebastián Apesteguía
>
> Fundación de Historia Natural 'Félix de Azara' -
> CEBBAD (CONICET) - Universidad Maimónides. Virasoro 732,
> Buenos Aires, ARGENTINA
> Tel-fax: 5411-49051100 ext. 1228,
> sebapesteguia@gmail.com, www.fundacionazara.org.ar
>