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RE: Ouranosaurus - how many species? Other "spino"-Igaunodontids?
Michael Mortimer <firstname.lastname@example.org> wrote:
> Don't forget Late Cretaceous taxa like Hypacrosaurus and
> Barsboldia. Then =
> you have some 'protoceratopsian' tails too=2C and Jurassic
> ids and Ceratosaurus had somewhat tall spines.
> Really=2C taxa with tall ne=
> ural spines were common=2C it's just that only a few are
> famous for it. =20
Those dinosaurs that are most famous for having tall neural spines tend to be
those that show the most extreme development of this condition - such as
_Spinosaurus_, _Amargasaurus_ and _Ouranosaurus_. In these forms, as with
_Dimetrodon_ and _Edaphosaurus_, the extreme elongation of the spines suggests
that they supported a membranous sail.
For those taxa that have 'tall-ish' spines, it's a much more open question
whether the spines supported a sail, or a ridge or hump. For example, the tall
spines of _Altispinax_ and _Metriacanthosaurus_ might have supported epaxial
musculature, rather than a sail.
Bailey (1997) proposed that ALL tall-spined dinosaurs had a "buffalo-style"
hump, for the purposes of fat storage. He even included restorations of
_Ouranosaurus_ and _Spinosaurus_ sporting giant humps! However, as fat-storing
devices, these humps would make them more like camels (which do *not* have tall
spines to support the adipose hump) than buffalos (where the hump is muscular,
and helps support the head). I think most workers would agree that a muscular
hump is a possibility for some dinosaurs with moderately tall spines; but it's
a stretch for the very tall-spined ones.
Bailey, Jack Bowman (1997). Neural spine elongation in dinosaurs: sailbacks or
buffalo-backs? J. Paleontol. 71: 1124-1146.