Re: More on Moser and prosauropod sacrals

["David Marjanovic" <david.marjanovic@gmx.at>]

> >   My only comment on this issue will be observation on one specimen of
> > *Silesaurus,* ZPAL Ab III/404, in which the sacrum is a
> > unified object of four vertebrae, comprising dorsosacrals 1 and 2, plus
> > the two primordial archosaurian sacrals, and no caudosacral,

> The well illustrated sacrum of Silesaurus IMHO confirms my position
> regarding Massospondylus: There are only two sacrals present (S1, S2, with
> key features that are present in S1 and S2 of Plateosaurus, Anchisaurus,
> Vulcanodon etc.). In Silesaurus the two last dorsals are fused to the
> sacrum. As these dorsals have no contact to the ilium,

I forgot something important. Under that definition, *Stegosaurus stenops*
has 4 sacrals (not 5, the "minimum" number for ornithischians), a
sacrodorsal (with normal, mobile dorsal ribs), and a sacrocaudal, assuming
that it isn't a free caudal that was just cast together with the sacrum and
ilia. I'm basing this on the skeletal cast in the geocenter here.

> as the term sacral is reserved for
> vertebrae that have a bony contact with the ilium.

In that case there are very few mammals with more than 1 or 2 sacrals. For
example, we don't have 6 then, just 2, + 4 sacrocaudals.