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Re: New sauropod paper



Mickey Mortimer (mickey_mortimer111@msn.com) wrote:

<Doesn't this just mean all of the specimens are syntypes?  A lectotype should
probably be chosen, but the name's hardly invalid.  Note Sereno chose a
lectotype for Elaphrosaurus gautieri when he renamed it Spinostropheus.>

  Syntypes are normally chosen from a collected bundle of bones whose reference
to one another is largely associated. Separation of Cope's syntypes for
*Coelophysis* into non-syntypic material resultes from this when Padian
reviewed the situation in 1989. A lectotype must be chosen from a syntype
series, but no such type series has been designated. That said....

Jay (sappororaptor@yahoo.com) wrote:


<If that's the case, then say bye to Jobaria. As mentioned above, there is a
lot of material mentioned above for R. tamesnensis. But question: how much of
this was collected and what was left in the field?  When i read the 1999
Jobaria paper years the ago, that footnote regarding R. tamesnensis didn't
sound definite....>

  The problem is is that a type specimen or series must bear the name, and must
be used to found features considered diagnostic of a species to be valid or
purposes of taxonomy and referal. De Lapparent failed, as was largely
conventional of his type, to designate any types.

  However, before we get into more Sereno-bashing, we should consider some
supportive philosophy here:

  Very little of de Lapparent's specimens derive from a single site, and
virtually none of it articulated, but were inferred based on stratigraphy and
approximation. Given the sauropods of a single horizon at Como Bluff, Wyoming
number over five distinct species, it was entirely possible that de Lapparent's
specimens did not all belong to a single taxon and, as in Como Bluff, may have
even represented similar species of a "family" grossly collected throughout the
Tiourarén Formation.

  Even though Sereno et al. could acknowledge they WERE of the same taxon he
and others had found near Agadéz, they had found more or less half-complete
skeletons of several age groups and were capable of describing associative
anatomies of a skeleton, which de Lapparent had to infer from assuming his
collection belonged to a single taxon.

  De Lapparent did not name a lectotype, and while Sereno et al. could have,
the collection of material had not undergone serious systematic review nor the
sauropods of the region or even vertical differentiation of the Tiourarén
affirmed their continuity (note that the Morrison Formation is divided into
members and some taxa of sauropod are found either above, below, or within
particular members, and some members) and thus Sereno felt it prudent to name a
taxon based on the best available material of the diagnostic sauropod material.

  Thus de Lapparent's name could be considered either a nomen nudum, or at most
a nomen dubium, and not healthy to use for limited material. Sereno et al.
diagnosed *Jobaria* based on total axial features, whereas reasonable
collections in de Lapparent's associations may have had only 1 or two features,
of which *Jobaria* is diagnostic due to the features collection, rather than 1
or 2 absolute apomorphies. The distribution, rather than the particulars, are
diagnostic in this case. Thus it is my opinion that Sereno et al. did the best
thing available with the material. Further material may then be referred based
on shared characters, but I figure much of it may not be referred.

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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