New Suuwassea paper

[Tim Williams <twilliams_alpha@hotmail.com>]

Harris, Jerald D. (2006).  The significance of _Suuwassea emiliae_ 
(Dinosauria: Sauropoda) for flagellicaudatan intrarelationships and 
evolution.  Journal of Systematic Palaeontology 4: 185-198.

SYNOPSIS: "_Suuwassea emilieae_ is a recently described dinosaur taxon 
discovered in the Upper
Jurassic Morrison Formation of thewesternUnited Statesandtheonly 
non-diplodocid flagellicaudatan (Dinosauria: Sauropoda) known from North 
America. It retains sauropod symplesiomorphies that are unexpected in a Late 
Jurassic taxon and thus sheds light on the evolutionary origins of the 
Flagellicaudata.  Despite being comparatively small, the holotype of 
_Suuwassea_ demonstrates hallmarks of relatively advanced age.  A 
phylogenetic analysis of 30 taxa and 331 characters retains _Suuwassea_ in a 
trichotomy with the Diplodocidae (_Apatosaurus_ + (_Diplodocus_ + 
_Barosaurus_)) and the Dicraeosauridae (_Dicraeosaurus_ + _Amargasaurus_).  
This lack of resolution is probably due to a combination of missing data, 
character conflict and poor incorporation of specimens referred to 
diplodocid taxa that differ from their holotype specimens and species 
holotypes.  Middle Jurassic palaeobiogeographical reconstructions conflict 
with the hypothetical distribution of flagellicaudatans in the Middle and 
Late Jurassic based on their phylogeny, implying that physical barriers, 
such as epeiric seas, were not responsible for limiting their initial 
radiation.  The postparietal foramen shared by _Suuwassea_, _Dicraeosaurus_, 
_Tornieria_ and _Amargasaurus_ may correlate to preferred existence in 
near-shore, terrestrial environments."

Also includes a summary of the status of Late Jurassic sauropods in North 
America.

_Amphicoelias_: Often considered nomen dubium or synonymous with either 
_Diplodocus_ or _Supersaurus_.  [I would add that McIntosh (2005) notes that 
the 'stovepipe'-like femur of _Amphicoelias_, which was once considered 
diagnostic, is also found in some _Diplodocus_ specimens.  Hopefully 
vertebral characters is enough to keep the genus _Amphicoelias_ valid.]

_Apatosaurus_: Valid.

_Camarasaurus_: Valid.

_Dystrophaeus_: Nomen dubium.  It comes from the Tidwell Member of the 
Summerville Formation (Anderson and Lucas, 1992; Lucas and Anderson, 1997), 
so it's not a Morrison sauropod.  [Darn, I was hoping _Dystrophaeus_ would 
be valid, given that it's North America's geologically earliest neosauropod 
(and sauropodiform?) genus.]

_Diplodocus_ Valid.

_?Morosaurus? agilis_: Status uncertain.  [I had thought this one had been 
referred to _Diplodocus longus_, by Tidwell et al. (2005).]

_Barosaurus_: Valid.

_Brachiosaurus: Valid.

_Haplocanthosaurus_: Valid.

_?Apatosaurus? minimus_: Status uncertain.

_Ultrasauros_:  Nomen dubium. Type scapulocoracoid referred to 
_Brachiosaurus_, type thoracic
vertebra referred to _Supersaurus_ (Curtice et al., 1996; Curtice and 
Wilhite, 1996).

_Dystylosaurus_: Nomen dubium.  Type caudal vertebra referred to 
_Supersaurus_ (Curtice and Stadtman, 2001).

_Supersaurus_: Provisionally valid.

_Cathetosaurus_:  Nomen dubium.  Synonymized with _Camarasaurus_, but 
retained as _C. lewisi_ (McIntosh et al., 1996).

_Seismosaurus_:  Nomen dubium.  Synonymized with _Diplodocus_, but possibly 
a distinct species (Lucas, 2000; Lucas et al. 2004).

_Dyslocosaurus_: Valid.  Possibly from the Lance Formation (Upper 
Cretaceous), not Morrison Formation.

_Eobrontosaurus_: Nomen dubium.  Synonymized with _Camarasaurus_ (Upchurch 
et al. 2004).  [I know that not everybody agrees with this.]

_Suuwassea_: Valid.

Lots of other good stuff too.  I can provide copies on request.

Cheers

Tim