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Re: Utahraptor;Argentine carnosaur
>I would greatly appreciate any and all information on both Utahraptor and the
>recently discovered Argentine giant carnosaur (i.e. dimensions,
>classifications, ages, etc.).
The Argentine giant predator ("carnosaur", if you insist on that archaic
term... ;-) ) has not yet been formally described, but will be soon. The
femur is about 1.44 m long (as compared to "Sue"'s, which is 1.38 m).
For Utahraptor, see KIRKLAND, J.I., BURGE, D., and GASTON, R. 1993. A
large dromaeosaur (Theropoda) from the Lower Cretaceous of eastern Utah.
Hunteria, 2(10), 1-16.
>Is the Argentine dinosaur a tyrannosaur? If so, then how did it get to South
>America? I thought South America was supposed to be isolated by the late
No, it isn't a tyrannosaurid. From what I've seen of it, it is either a
very derived abelisaurid (giant theropods related to Ceratosaurus), or a
primitive tetanurine (the favored hypothesis of the describers). I suspect
it may be closely related to Carcharodontosaurus and Bahariasaurus ;-) [A
joke, since no one has satisfactorily deteremined where these two theropods
fit in the family tree. It must be noted, though: both of these giant
theropod lived at about the same time as the new Argentine form].
South America is not particularly isolated during this interval. A
fragmentary spinosaurid is known from South America during this time, while
Spinosaurus itself is found in northern Africa. The east African
Malawisaurus and European titanosaurids resemble the titanosaurids of South
America from this interval. There is also sauropod material which
Argentine paleontologists have referred to Rebbachisaurus, a northern
>Sauropods existed to the end of the Cretaceous, and, in Titanosaurids,
>possibly even became larger, yet sauropods are mostly discussed in a Jurassic
>context. Why don't we hear more about the later sauropods?
One part jingoism (there are no complete sauropod skeletons from the
Cretaceous of the U.S., as opposed to excellent skeletons from the Late
Jurassic Morrison Formation). However, some of the South American (and now
northern African) Cretaceous sauropods are fairly complete, so hopefully we
can see some of them in future illustrations. Already Amargasaurus, from
the Early Cretaceous of Argentina, is showing up in dinosaur books and
magazines in the U.S. and elsewhere.
>Were they simply
>that much less common? Weren't they the only animals capable of fulfilling
>their ecological niches?
In some parts of the world, they were as common as ever. Although no
nonsauropod reached the >20 or >30 tonne range (as far as we know), there
were Late Cretaceous hadrosaurids which grew in excess of 10, or even 15
tonnes (Shangtungosaurus, Lambeosaurus? laticaudus).
>Finally, why would anyone suspect that dinosaurs were anything but
>warm-blooded? It seems bloody obvious to me...
For some recent thoughts on this, check out Jim Farlow's chapter in _The
Dinosauria_ and the references within.
Thomas R. Holtz, Jr.
Vertebrate Paleontologist in Exile Phone: 703-648-5280
U.S. Geological Survey FAX: 703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA 22092