>I was checking out Stephen Czerkas' drawing of _Diploducus_,
and the dorsal spines in the reconstruction. I also remember >seeing
similar spines on a drawing by Greg Paul of a _Brachiosaurus_ for The
Dinosaur Encyclopedia. Is it generally accepted >that many sauropods had
Not really. Greg Paul one of the few artists who put such spines on
almost every sauropod. There of course is some evidence for them, but was
(as far as I know) found only one time, on a diplodocid.
>How similar are these spines to those on, say, an
_Amargasaurus_ or _Dicraeosaurus_?
Nothing similar. Dicraeosaurids' "spines" are just elongated
split vertebral neural arches. They are not separate structures. Les spines
that may have partly covered some sauropods were in fact not even ossified
(bony). They may well have been scattered on the whole body of every
sauropod, but they could also have been just a little row on the back of
just one diplodocid.