Re: remains of spinosauridae

["Mickey Mortimer" <Mickey_Mortimer111@msn.com>]

Jaime Headden wrote-

> <Yeah, but S. maroccanus is considered a junior synonym of S. aegyptiacus
> now anyway.>
>
>   Isn't it funny how when someone publishes a statement saying that two
> taxa are similar, and it's so convincingly done (such as Sereno et al.'s
> single sentence in 1998, the description of *Suchomimus*), "he" becomes
> "everyone?" Not everyone holds this view of synonymy, such as Dale
> Russell, and despite the attempt, *S. maroccanus* does have distinct
> cervical morphology, however age-related it might be. Based on the lost
> type of *S. aegyptiacus,* the quality of comparison is robust; it is my
> observation that the opinion of Sereno et al. is based on the limited type
> (a single vertebra) to which only other regionally found vertebrae were
> found. This does not reduce the quality of the diagnosis. Perhaps *S.
> maroccanus* can be a nomen dubium, but frankly, the centrum proportions
> versus the shorter neural spine to size distinguishes the two species.

Oh, I agree completely regarding the amusing habit of following terse (often
unsupported) suggestions of synonymy and diagnosability.  I especially hate
it when someone is reviewing species belonging to a higher taxon or coming
from a particular location, and doesn't want to deal with the poorly known
forms.  So they'll just say they are indeterminate, and cite something like
The Dinosauria, which listed nomina dubia without any support.
Regarding S. marocannus, Sereno et al. rejected its validity because the
only character given in the diagnosis to distinguish it from S. aegyptiacus
was the longer cervical centra, and they thought this varied within the
vertebral column.  S. aegyptiacus preserves two cervicals, one of which is
possibly the axis, and the other from the middle of the neck.  The latter's
centrum has a length to posterior height ratio of 1.05.  The two relatively
complete cervicals of S. marocannus have ratios of 1.39 and 1.60.  Ratios in
Baryonyx's holotype range from 1.25-1.81, which is the same amount of
variation supposedly separating the Spinosaurus species.  Neural spines are
comparable in height between Spinosaurus species, and anteroposterior length
of the spine varies with centrum elongation as seen in Baryonyx.  The latter
shows similar differences between cervicals 6 and 8 as seen between S.
aegyptiacus and S. marocannus.  Russell states besides the elongation noted
above and of the neural peduncle (also seen in Baryonyx), the cervicals of
the two Spinosaurus species are very similar.  The dentaries are also
"essentially indistinguishable".  Thus, I must agree with Sereno that S.
marocannus is a junior synonym of S. aegyptiacus.

Mickey Mortimer