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Amargosaurus, Argentinian but not Titanosaur!



>Has anyone seen any fossil material from Amargasaurus, the Argentine sauropod
>with exceedingly long dual veterbral processes that create a double row of
>"sails." 

Incidentally, the original reference for this new sauropod is:
Salgado, L. and J.F. Bonaparte.  1991.  Un nuevo sauropodo Dicraeosauridae,
Amargasaurus cazaui gen. et sp. nov., de la Formacion La Amarga, neocomiano
de la Provincia del Neque'n, Argentina.  Ameghiniana, 28:333-346.

>   Does anyone have any idea if this feature may have been a double sail or a
>single wide ridge with connective materials between the two processes?

I suspect it was a double sail.  Some illustrators show the tips of the
spines protruding from the sails, but this is an extraordinarily rare
condition in tetrapods, so I suspect all the spines were within flesh. 
Along the base of the bifurcation there was probably a series of tendons,
as is suspected between the much smaller spines in Diplodocus (see
Alexander's Dynamics of Dinosaurs for a discussion of the purpose of said
tendons).

>   I am writing a piece for the soon to be launched magazine  (ages 7 to 16)
>Dinosaurus, and I want to resolve some questions about this beast,
>particularly for illustrative purposes.
>   I need to know something about the animal's normal Jurassic-early
>Cretaceous habitat. It appears to be a Titanosaur. What anatomical features
>are indicative of Titanosaurs?

Amaragasaurus is most certainly NOT a titanosaurian.  It is instead a
member of the Dicraeosauridae, and its closest known relative is
Dicraeosaurus of Late Jurassic Africa.  It is somewhat more distantly
related to Diplodocus, Apatosaurus, and the other Diplodocidae.

Characteristics of the braincase, the sloping skull, and especially the
bifurcated neural spines are indicative of it being a dicraeosaurid. 
Diplodocids and camamarasaurids (but not titanosaurids) have neural spines
with bifurcations, but in dicraeosaurids these spines are very elongate.

Also, Amaragasaurus is only known from the Early Cretaceous.  Little is
known of the habitat of this animal, but slightly younger dinosaurs from
the same region include the giant titanosaurian Argentinosaurus, the
smaller Andesaurus, and the horned predator Carnotaurus.

>   I would also like to ask if anyone out there is an illustrator. I can use
>samples of work to see if I can put together a stable of illustrators for the
>publication. Someone responded to this question a month ago, but I lost the
>correspondence. Please reply: Pterodan@aol.com. Or write Kim Robert Nilsen,
>Dinosaurus Magazine, HCR10, Box 152, Keene, NH 03431.

Good luck with your magazine.
                                     

                                
Thomas R. Holtz, Jr.
Vertebrate Paleontologist in Exile
U.S. Geological Survey
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092

email:  tholtz@geochange.er.usgs.gov 
Phone:  703-648-5280
FAX:            703-648-5420