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Agustinia ligabuei



Hi all,

I'm going to ask a potentially very silly question: how certain can we
be that the osteoderms (particularly types 3 and 4) of *Agustinia
ligabuei* Bonaparte, 1999 are actually osteoderms? Is it possible that
they are just misidentified transverse processes / sacral ribs
(compare the base of the osteoderm (but rotate it upside down) in
Bonaparte (1999) to Figure 23.B in Curry Rogers (2009), for example)?
If so, then the sacrum would have to have been at least a third wider
than it is long (though I don't 100% trust the scale bars for the
dimensions of the sacral vertebrae - in Bonaparte (1999), Figure 1
suggests that they are ~11cm long, whilst Figure 2 suggests ~67cm...).
Novas (2009) follows Bonaparte's (1999) Figure 2, and based on his
Figure 5.4 (p. 173; presuming his scaling of the osteoderms is
correct) the breadth of the pelvis (without the ilia) would be ~91cm.

The identity of the Type 2 osteoderm (640mm transverse length) is a
bit more problematic; could it be the fused ischia, viewed dorsally?
Similarly problematic is the type 4 osteoderm in Figure 5 of Bonaparte
(1999) which was 760mm long; could this be a dorsal rib?

The only images I am able to find of the holotype specimens are those
in the original paper and the rearranged images in Novas, 2009. The
discussions of Salgado & Bonaparte (2007) and Upchurch et al. (2004)
don't add much to the original description, the codings for
*Augustinia* [sic] in Curry Rogers 2005 appear not to actually
correspond to *Agustinia*, and I've had no luck finding any images on
the internet. Have I missed any important references to this specimen?
Do any photos and / or a quarry map exist somewhere, I wonder?

If I'm completely off the track here, please let me know, it's just
that I've been looking at Bonaparte's figures and struggling to
believe the interpretation. This taxon is definitely in need of
redescription and re-illustration... or (wishfully thinking) another,
more complete specimen!

Cheers,

Steve

Bonaparte, J.F., 1999. An armoured sauropod from the Aptian of
northern Patagonia, Argentina, In: Tomida, Y., Rich, T.H.,
Vickers-Rich, P. (Eds.), Second Gondwanan Dinosaur Symposium: National
Science Museum Monograph, 15, Tokyo, pp. 1-12.
Curry Rogers, K.A., 2005. Titanosauria: a phylogenetic overview, In:
Curry Rogers, K.A., Wilson, J.A. (Eds.), The Sauropods: Evolution and
Paleobiology. University of California Press, Berkeley, pp. 50-103.
Curry Rogers, K., 2009. The postcranial osteology of *Rapetosaurus
krausei* (Sauropoda: Titanosauria) from the Late Cretaceous of
Madagascar. Journal of Vertebrate Paleontology 29, 1046-1086.
Novas, F.E., 2009. Cretaceous sauropods, In: Novas, F.E. (Ed.), The
Age of Dinosaurs in South America. Indiana University Press,
Bloomington, pp. 166-241.
Salgado, L., Bonaparte, J.F., 2007. Sauropodomorpha, In: Gasparini,
Z., Salgado, L., Coria, R.A. (Eds.), Patagonian Mesozoic Reptiles.
Indiana University Press, Bloomington, pp. 188-228.
Upchurch, P., Barrett, P.M., Dodson, P., 2004. Sauropoda, In:
Weishampel, D.B., Dodson, P., Osmólska, H. (Eds.), The Dinosauria:
Second Edition. University of California Press, Berkeley, pp. 259-322.

--
Dr. Stephen Poropat

Postdoctoral Research Fellow
Uppsala University
Villavägen 16
SE-752 36 Uppsala
Sweden

Research Associate
Australian Age of Dinosaurs
PO Box 408
Winton 4735
Australia